/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * Handling of regular expressions: vim_regcomp(), vim_regexec(), vim_regsub()
 *
 * NOTICE:
 *
 * This is NOT the original regular expression code as written by Henry
 * Spencer.  This code has been modified specifically for use with the VIM
 * editor, and should not be used separately from Vim.  If you want a good
 * regular expression library, get the original code.  The copyright notice
 * that follows is from the original.
 *
 * END NOTICE
 *
 *	Copyright (c) 1986 by University of Toronto.
 *	Written by Henry Spencer.  Not derived from licensed software.
 *
 *	Permission is granted to anyone to use this software for any
 *	purpose on any computer system, and to redistribute it freely,
 *	subject to the following restrictions:
 *
 *	1. The author is not responsible for the consequences of use of
 *		this software, no matter how awful, even if they arise
 *		from defects in it.
 *
 *	2. The origin of this software must not be misrepresented, either
 *		by explicit claim or by omission.
 *
 *	3. Altered versions must be plainly marked as such, and must not
 *		be misrepresented as being the original software.
 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 *
 * Changes have been made by Tony Andrews, Olaf 'Rhialto' Seibert, Robert
 * Webb, Ciaran McCreesh and Bram Moolenaar.
 * Named character class support added by Walter Briscoe (1998 Jul 01)
 */

// By default: do not create debugging logs or files related to regular
// expressions, even when compiling with -DDEBUG.
// Uncomment the second line to get the regexp debugging.
#undef DEBUG
// #define DEBUG

#include "vim.h"

#ifdef DEBUG
/* show/save debugging data when BT engine is used */
#define BT_REGEXP_DUMP
/* save the debugging data to a file instead of displaying it */
#define BT_REGEXP_LOG
#define BT_REGEXP_DEBUG_LOG
#define BT_REGEXP_DEBUG_LOG_NAME "bt_regexp_debug.log"
#endif

/*
 * The "internal use only" fields in regexp.h are present to pass info from
 * compile to execute that permits the execute phase to run lots faster on
 * simple cases.  They are:
 *
 * regstart	char that must begin a match; NUL if none obvious; Can be a
 *		multi-byte character.
 * reganch	is the match anchored (at beginning-of-line only)?
 * regmust	string (pointer into program) that match must include, or NULL
 * regmlen	length of regmust string
 * regflags	RF_ values or'ed together
 *
 * Regstart and reganch permit very fast decisions on suitable starting points
 * for a match, cutting down the work a lot.  Regmust permits fast rejection
 * of lines that cannot possibly match.  The regmust tests are costly enough
 * that vim_regcomp() supplies a regmust only if the r.e. contains something
 * potentially expensive (at present, the only such thing detected is * or +
 * at the start of the r.e., which can involve a lot of backup).  Regmlen is
 * supplied because the test in vim_regexec() needs it and vim_regcomp() is
 * computing it anyway.
 */

/*
 * Structure for regexp "program".  This is essentially a linear encoding
 * of a nondeterministic finite-state machine (aka syntax charts or
 * "railroad normal form" in parsing technology).  Each node is an opcode
 * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
 * all nodes except BRANCH and BRACES_COMPLEX implement concatenation; a "next"
 * pointer with a BRANCH on both ends of it is connecting two alternatives.
 * (Here we have one of the subtle syntax dependencies:	an individual BRANCH
 * (as opposed to a collection of them) is never concatenated with anything
 * because of operator precedence).  The "next" pointer of a BRACES_COMPLEX
 * node points to the node after the stuff to be repeated.
 * The operand of some types of node is a literal string; for others, it is a
 * node leading into a sub-FSM.  In particular, the operand of a BRANCH node
 * is the first node of the branch.
 * (NB this is *not* a tree structure: the tail of the branch connects to the
 * thing following the set of BRANCHes.)
 *
 * pattern	is coded like:
 *
 *			  +-----------------+
 *			  |		    V
 * <aa>\|<bb>	BRANCH <aa> BRANCH <bb> --> END
 *		     |	    ^	 |	    ^
 *		     +------+	 +----------+
 *
 *
 *		       +------------------+
 *		       V		  |
 * <aa>*	BRANCH BRANCH <aa> --> BACK BRANCH --> NOTHING --> END
 *		     |	    |		    ^			   ^
 *		     |	    +---------------+			   |
 *		     +---------------------------------------------+
 *
 *
 *		       +----------------------+
 *		       V		      |
 * <aa>\+	BRANCH <aa> --> BRANCH --> BACK  BRANCH --> NOTHING --> END
 *		     |		     |		 ^			^
 *		     |		     +-----------+			|
 *		     +--------------------------------------------------+
 *
 *
 *					+-------------------------+
 *					V			  |
 * <aa>\{}	BRANCH BRACE_LIMITS --> BRACE_COMPLEX <aa> --> BACK  END
 *		     |				    |		     ^
 *		     |				    +----------------+
 *		     +-----------------------------------------------+
 *
 *
 * <aa>\@!<bb>	BRANCH NOMATCH <aa> --> END  <bb> --> END
 *		     |	     |		      ^       ^
 *		     |	     +----------------+       |
 *		     +--------------------------------+
 *
 *						      +---------+
 *						      |		V
 * \z[abc]	BRANCH BRANCH  a  BRANCH  b  BRANCH  c	BRANCH	NOTHING --> END
 *		     |	    |	       |	  |	^		    ^
 *		     |	    |	       |	  +-----+		    |
 *		     |	    |	       +----------------+		    |
 *		     |	    +---------------------------+		    |
 *		     +------------------------------------------------------+
 *
 * They all start with a BRANCH for "\|" alternatives, even when there is only
 * one alternative.
 */

/*
 * The opcodes are:
 */

// clang-format off

/* definition	number		   opnd?    meaning */
#define END 0           /*	End of program or NOMATCH operand. */
#define BOL 1           /*	Match "" at beginning of line. */
#define EOL 2           /*	Match "" at end of line. */
#define BRANCH 3        /* node Match this alternative, or the \
                         *	next... */
#define BACK 4          /*	Match "", "next" ptr points backward. */
#define EXACTLY 5       /* str	Match this string. */
#define NOTHING 6       /*	Match empty string. */
#define STAR 7          /* node Match this (simple) thing 0 or more \
                         *	times. */
#define PLUS 8          /* node Match this (simple) thing 1 or more \
                         *	times. */
#define MATCH 9         /* node match the operand zero-width */
#define NOMATCH 10      /* node check for no match with operand */
#define BEHIND 11       /* node look behind for a match with operand */
#define NOBEHIND 12     /* node look behind for no match with operand */
#define SUBPAT 13       /* node match the operand here */
#define BRACE_SIMPLE 14 /* node Match this (simple) thing between m and \
                         *	n times (\{m,n\}). */
#define BOW 15          /*	Match "" after [^a-zA-Z0-9_] */
#define EOW 16          /*	Match "" at    [^a-zA-Z0-9_] */
#define BRACE_LIMITS 17 /* nr nr  define the min & max for BRACE_SIMPLE \
                         *	and BRACE_COMPLEX. */
#define NEWL 18         /*	Match line-break */
#define BHPOS 19        /*	End position for BEHIND or NOBEHIND */

// clang-format off

/* character classes: 20-48 normal, 50-78 include a line-break */
#define ADD_NL 30
#define FIRST_NL ANY + ADD_NL
#define ANY 20    /*	Match any one character. */
#define ANYOF 21  /* str	Match any character in this string. */
#define ANYBUT 22 /* str	Match any character not in this \
                   *	string. */
#define IDENT 23  /*	Match identifier char */
#define SIDENT 24 /*	Match identifier char but no digit */
#define KWORD 25  /*	Match keyword char */
#define SKWORD 26 /*	Match word char but no digit */
#define FNAME 27  /*	Match file name char */
#define SFNAME 28 /*	Match file name char but no digit */
#define PRINT 29  /*	Match printable char */
#define SPRINT 30 /*	Match printable char but no digit */
#define WHITE 31  /*	Match whitespace char */
#define NWHITE 32 /*	Match non-whitespace char */
#define DIGIT 33  /*	Match digit char */
#define NDIGIT 34 /*	Match non-digit char */
#define HEX 35    /*	Match hex char */
#define NHEX 36   /*	Match non-hex char */
#define OCTAL 37  /*	Match octal char */
#define NOCTAL 38 /*	Match non-octal char */
#define WORD 39   /*	Match word char */
#define NWORD 40  /*	Match non-word char */
#define HEAD 41   /*	Match head char */
#define NHEAD 42  /*	Match non-head char */
#define ALPHA 43  /*	Match alpha char */
#define NALPHA 44 /*	Match non-alpha char */
#define LOWER 45  /*	Match lowercase char */
#define NLOWER 46 /*	Match non-lowercase char */
#define UPPER 47  /*	Match uppercase char */
#define NUPPER 48 /*	Match non-uppercase char */
#define LAST_NL NUPPER + ADD_NL
#define WITH_NL(op) ((op) >= FIRST_NL && (op) <= LAST_NL)

#define MOPEN 80    /* -89	 Mark this point in input as start of \
                     *	 \( subexpr.  MOPEN + 0 marks start of    \
                     *	 match. */
#define MCLOSE 90   /* -99	 Analogous to MOPEN.  MCLOSE + 0 marks \
                     *	 end of match. */
#define BACKREF 100 /* -109 node Match same string again \1-\9 */

#define BRACE_COMPLEX 140 /* -149 node Match nodes between m & n times */

#define NOPEN 150  /*	Mark this point in input as start of \
                           \%( subexpr. */
#define NCLOSE 151 /*	Analogous to NOPEN. */

#define MULTIBYTECODE 200 /* mbc	Match one multi-byte character */
#define RE_BOF 201        /*	Match "" at beginning of file. */
#define RE_EOF 202        /*	Match "" at end of file. */
#define CURSOR 203        /*	Match location of cursor. */

#define RE_LNUM 204 /* nr cmp  Match line number */
#define RE_COL 205  /* nr cmp  Match column number */
#define RE_VCOL 206 /* nr cmp  Match virtual column number */

#define RE_MARK 207      /* mark cmp  Match mark position */
#define RE_VISUAL 208    /*	Match Visual area */
#define RE_COMPOSING 209 /* any composing characters */

/*
 * Magic characters have a special meaning, they don't match literally.
 * Magic characters are negative.  This separates them from literal characters
 * (possibly multi-byte).  Only ASCII characters can be Magic.
 */
#define Magic(x) ((int)(x)-256)
#define un_Magic(x) ((x) + 256)
#define is_Magic(x) ((x) < 0)

// clang-format on

static int
no_Magic(int x)
{
  if (is_Magic(x))
    return un_Magic(x);
  return x;
}

static int
toggle_Magic(int x)
{
  if (is_Magic(x))
    return un_Magic(x);
  return Magic(x);
}

/*
 * The first byte of the regexp internal "program" is actually this magic
 * number; the start node begins in the second byte.  It's used to catch the
 * most severe mutilation of the program by the caller.
 */

#define REGMAGIC 0234

/*
 * Opcode notes:
 *
 * BRANCH	The set of branches constituting a single choice are hooked
 *		together with their "next" pointers, since precedence prevents
 *		anything being concatenated to any individual branch.  The
 *		"next" pointer of the last BRANCH in a choice points to the
 *		thing following the whole choice.  This is also where the
 *		final "next" pointer of each individual branch points; each
 *		branch starts with the operand node of a BRANCH node.
 *
 * BACK		Normal "next" pointers all implicitly point forward; BACK
 *		exists to make loop structures possible.
 *
 * STAR,PLUS	'=', and complex '*' and '+', are implemented as circular
 *		BRANCH structures using BACK.  Simple cases (one character
 *		per match) are implemented with STAR and PLUS for speed
 *		and to minimize recursive plunges.
 *
 * BRACE_LIMITS	This is always followed by a BRACE_SIMPLE or BRACE_COMPLEX
 *		node, and defines the min and max limits to be used for that
 *		node.
 *
 * MOPEN,MCLOSE	...are numbered at compile time.
 * ZOPEN,ZCLOSE	...ditto
 */

/*
 * A node is one char of opcode followed by two chars of "next" pointer.
 * "Next" pointers are stored as two 8-bit bytes, high order first.  The
 * value is a positive offset from the opcode of the node containing it.
 * An operand, if any, simply follows the node.  (Note that much of the
 * code generation knows about this implicit relationship.)
 *
 * Using two bytes for the "next" pointer is vast overkill for most things,
 * but allows patterns to get big without disasters.
 */
#define OP(p) ((int)*(p))
#define NEXT(p) (((*((p) + 1) & 0377) << 8) + (*((p) + 2) & 0377))
#define OPERAND(p) ((p) + 3)
/* Obtain an operand that was stored as four bytes, MSB first. */
#define OPERAND_MIN(p) (((long)(p)[3] << 24) + ((long)(p)[4] << 16) + ((long)(p)[5] << 8) + (long)(p)[6])
/* Obtain a second operand stored as four bytes. */
#define OPERAND_MAX(p) OPERAND_MIN((p) + 4)
/* Obtain a second single-byte operand stored after a four bytes operand. */
#define OPERAND_CMP(p) (p)[7]

/*
 * Utility definitions.
 */
#define UCHARAT(p) ((int)*(char_u *)(p))

/* Used for an error (down from) vim_regcomp(): give the error message, set
 * rc_did_emsg and return NULL */
#define EMSG_RET_NULL(m) return (emsg((m)), rc_did_emsg = TRUE, (void *)NULL)
#define IEMSG_RET_NULL(m) return (iemsg((m)), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG_RET_FAIL(m) return (emsg((m)), rc_did_emsg = TRUE, FAIL)
#define EMSG2_RET_NULL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG3_RET_NULL(m, c, a) return (semsg((const char *)(m), (c) ? "" : "\\", (a)), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG2_RET_FAIL(m, c) return (semsg((const char *)(m), (c) ? "" : "\\"), rc_did_emsg = TRUE, FAIL)
#define EMSG_ONE_RET_NULL EMSG2_RET_NULL(_("E369: invalid item in %s%%[]"), reg_magic == MAGIC_ALL)

#define MAX_LIMIT (32767L << 16L)

static int cstrncmp(char_u *s1, char_u *s2, int *n);
static char_u *cstrchr(char_u *, int);

#ifdef BT_REGEXP_DUMP
static void regdump(char_u *, bt_regprog_T *);
#endif
#ifdef DEBUG
static char_u *regprop(char_u *);
#endif

static int re_mult_next(char *what);

static char_u e_missingbracket[] = N_("E769: Missing ] after %s[");
static char_u e_reverse_range[] = N_("E944: Reverse range in character class");
static char_u e_large_class[] = N_("E945: Range too large in character class");
static char_u e_unmatchedpp[] = N_("E53: Unmatched %s%%(");
static char_u e_unmatchedp[] = N_("E54: Unmatched %s(");
static char_u e_unmatchedpar[] = N_("E55: Unmatched %s)");
static char_u e_missing_sb[] = N_("E69: Missing ] after %s%%[");
static char_u e_empty_sb[] = N_("E70: Empty %s%%[]");
static char_u e_recursive[] = N_("E956: Cannot use pattern recursively");

#define NOT_MULTI 0
#define MULTI_ONE 1
#define MULTI_MULT 2
/*
 * Return NOT_MULTI if c is not a "multi" operator.
 * Return MULTI_ONE if c is a single "multi" operator.
 * Return MULTI_MULT if c is a multi "multi" operator.
 */
static int
re_multi_type(int c)
{
  if (c == Magic('@') || c == Magic('=') || c == Magic('?'))
    return MULTI_ONE;
  if (c == Magic('*') || c == Magic('+') || c == Magic('{'))
    return MULTI_MULT;
  return NOT_MULTI;
}

/*
 * Flags to be passed up and down.
 */
#define HASWIDTH 0x1   /* Known never to match null string. */
#define SIMPLE 0x2     /* Simple enough to be STAR/PLUS operand. */
#define SPSTART 0x4    /* Starts with * or +. */
#define HASNL 0x8      /* Contains some \n. */
#define HASLOOKBH 0x10 /* Contains "\@<=" or "\@<!". */
#define WORST 0        /* Worst case. */

/*
 * When regcode is set to this value, code is not emitted and size is computed
 * instead.
 */
#define JUST_CALC_SIZE ((char_u *)-1)

static char_u *reg_prev_sub = NULL;

/*
 * REGEXP_INRANGE contains all characters which are always special in a []
 * range after '\'.
 * REGEXP_ABBR contains all characters which act as abbreviations after '\'.
 * These are:
 *  \n	- New line (NL).
 *  \r	- Carriage Return (CR).
 *  \t	- Tab (TAB).
 *  \e	- Escape (ESC).
 *  \b	- Backspace (Ctrl_H).
 *  \d  - Character code in decimal, eg \d123
 *  \o	- Character code in octal, eg \o80
 *  \x	- Character code in hex, eg \x4a
 *  \u	- Multibyte character code, eg \u20ac
 *  \U	- Long multibyte character code, eg \U12345678
 */
static char_u REGEXP_INRANGE[] = "]^-n\\";
static char_u REGEXP_ABBR[] = "nrtebdoxuU";

/*
 * Translate '\x' to its control character, except "\n", which is Magic.
 */
static int
backslash_trans(int c)
{
  switch (c)
  {
  case 'r':
    return CAR;
  case 't':
    return TAB;
  case 'e':
    return ESC;
  case 'b':
    return BS;
  }
  return c;
}

/*
 * Check for a character class name "[:name:]".  "pp" points to the '['.
 * Returns one of the CLASS_ items. CLASS_NONE means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
static int
get_char_class(char_u **pp)
{
  static const char *(class_names[]) =
      {
          "alnum:]",
#define CLASS_ALNUM 0
          "alpha:]",
#define CLASS_ALPHA 1
          "blank:]",
#define CLASS_BLANK 2
          "cntrl:]",
#define CLASS_CNTRL 3
          "digit:]",
#define CLASS_DIGIT 4
          "graph:]",
#define CLASS_GRAPH 5
          "lower:]",
#define CLASS_LOWER 6
          "print:]",
#define CLASS_PRINT 7
          "punct:]",
#define CLASS_PUNCT 8
          "space:]",
#define CLASS_SPACE 9
          "upper:]",
#define CLASS_UPPER 10
          "xdigit:]",
#define CLASS_XDIGIT 11
          "tab:]",
#define CLASS_TAB 12
          "return:]",
#define CLASS_RETURN 13
          "backspace:]",
#define CLASS_BACKSPACE 14
          "escape:]",
#define CLASS_ESCAPE 15
          "ident:]",
#define CLASS_IDENT 16
          "keyword:]",
#define CLASS_KEYWORD 17
          "fname:]",
#define CLASS_FNAME 18
      };
#define CLASS_NONE 99
  int i;

  if ((*pp)[1] == ':')
  {
    for (i = 0; i < (int)(sizeof(class_names) / sizeof(*class_names)); ++i)
      if (STRNCMP(*pp + 2, class_names[i], STRLEN(class_names[i])) == 0)
      {
        *pp += STRLEN(class_names[i]) + 2;
        return i;
      }
  }
  return CLASS_NONE;
}

/*
 * Specific version of character class functions.
 * Using a table to keep this fast.
 */
static short class_tab[256];

#define RI_DIGIT 0x01
#define RI_HEX 0x02
#define RI_OCTAL 0x04
#define RI_WORD 0x08
#define RI_HEAD 0x10
#define RI_ALPHA 0x20
#define RI_LOWER 0x40
#define RI_UPPER 0x80
#define RI_WHITE 0x100

static void
init_class_tab(void)
{
  int i;
  static int done = FALSE;

  if (done)
    return;

  for (i = 0; i < 256; ++i)
  {
    if (i >= '0' && i <= '7')
      class_tab[i] = RI_DIGIT + RI_HEX + RI_OCTAL + RI_WORD;
    else if (i >= '8' && i <= '9')
      class_tab[i] = RI_DIGIT + RI_HEX + RI_WORD;
    else if (i >= 'a' && i <= 'f')
      class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
#ifdef EBCDIC
    else if ((i >= 'g' && i <= 'i') || (i >= 'j' && i <= 'r') || (i >= 's' && i <= 'z'))
#else
    else if (i >= 'g' && i <= 'z')
#endif
      class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
    else if (i >= 'A' && i <= 'F')
      class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
#ifdef EBCDIC
    else if ((i >= 'G' && i <= 'I') || (i >= 'J' && i <= 'R') || (i >= 'S' && i <= 'Z'))
#else
    else if (i >= 'G' && i <= 'Z')
#endif
      class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
    else if (i == '_')
      class_tab[i] = RI_WORD + RI_HEAD;
    else
      class_tab[i] = 0;
  }
  class_tab[' '] |= RI_WHITE;
  class_tab['\t'] |= RI_WHITE;
  done = TRUE;
}

#define ri_digit(c) (c < 0x100 && (class_tab[c] & RI_DIGIT))
#define ri_hex(c) (c < 0x100 && (class_tab[c] & RI_HEX))
#define ri_octal(c) (c < 0x100 && (class_tab[c] & RI_OCTAL))
#define ri_word(c) (c < 0x100 && (class_tab[c] & RI_WORD))
#define ri_head(c) (c < 0x100 && (class_tab[c] & RI_HEAD))
#define ri_alpha(c) (c < 0x100 && (class_tab[c] & RI_ALPHA))
#define ri_lower(c) (c < 0x100 && (class_tab[c] & RI_LOWER))
#define ri_upper(c) (c < 0x100 && (class_tab[c] & RI_UPPER))
#define ri_white(c) (c < 0x100 && (class_tab[c] & RI_WHITE))

/* flags for regflags */
#define RF_ICASE 1    /* ignore case */
#define RF_NOICASE 2  /* don't ignore case */
#define RF_HASNL 4    /* can match a NL */
#define RF_ICOMBINE 8 /* ignore combining characters */
#define RF_LOOKBH 16  /* uses "\@<=" or "\@<!" */

/*
 * Global work variables for vim_regcomp().
 */

static char_u *regparse;             /* Input-scan pointer. */
static int prevchr_len;              /* byte length of previous char */
static int num_complex_braces;       /* Complex \{...} count */
static int regnpar;                  /* () count. */
static char_u *regcode;              /* Code-emit pointer, or JUST_CALC_SIZE */
static long regsize;                 /* Code size. */
static int reg_toolong;              /* TRUE when offset out of range */
static char_u had_endbrace[NSUBEXP]; /* flags, TRUE if end of () found */
static unsigned regflags;            /* RF_ flags for prog */
static long brace_min[10];           /* Minimums for complex brace repeats */
static long brace_max[10];           /* Maximums for complex brace repeats */
static int brace_count[10];          /* Current counts for complex brace repeats */
static int one_exactly = FALSE;      /* only do one char for EXACTLY */

static int reg_magic; /* magicness of the pattern: */
#define MAGIC_NONE 1  /* "\V" very unmagic */
#define MAGIC_OFF 2   /* "\M" or 'magic' off */
#define MAGIC_ON 3    /* "\m" or 'magic' */
#define MAGIC_ALL 4   /* "\v" very magic */

static int reg_string; /* matching with a string instead of a buffer
				   line */
static int reg_strict; /* "[abc" is illegal */

/*
 * META contains all characters that may be magic, except '^' and '$'.
 */

#ifdef EBCDIC
static char_u META[] = "%&()*+.123456789<=>?@ACDFHIKLMOPSUVWX[_acdfhiklmnopsuvwxz{|~";
#else
/* META[] is used often enough to justify turning it into a table. */
static char_u META_flags[] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    /*		   %  &     (  )  *  +	      .    */
    0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 0,
    /*     1  2  3	4  5  6  7  8  9	<  =  >  ? */
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1,
    /*  @  A     C	D     F     H  I     K	L  M	 O */
    1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1,
    /*  P	     S	   U  V  W  X	  Z  [		 _ */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1,
    /*     a     c	d     f     h  i     k	l  m  n  o */
    0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
    /*  p	     s	   u  v  w  x	  z  {	|     ~    */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1};
#endif

static int curchr; /* currently parsed character */
/* Previous character.  Note: prevchr is sometimes -1 when we are not at the
 * start, eg in /[ ^I]^ the pattern was never found even if it existed,
 * because ^ was taken to be magic -- webb */
static int prevchr;
static int prevprevchr; /* previous-previous character */
static int nextchr;     /* used for ungetchr() */

/* arguments for reg() */
#define REG_NOPAREN 0 /* toplevel reg() */
#define REG_PAREN 1   /* \(\) */
#define REG_ZPAREN 2  /* \z(\) */
#define REG_NPAREN 3  /* \%(\) */

typedef struct
{
  char_u *regparse;
  int prevchr_len;
  int curchr;
  int prevchr;
  int prevprevchr;
  int nextchr;
  int at_start;
  int prev_at_start;
  int regnpar;
} parse_state_T;

/*
 * Forward declarations for vim_regcomp()'s friends.
 */
static void initchr(char_u *);
static int getchr(void);
static void skipchr_keepstart(void);
static int peekchr(void);
static void skipchr(void);
static void ungetchr(void);
static long gethexchrs(int maxinputlen);
static long getoctchrs(void);
static long getdecchrs(void);
static int coll_get_char(void);
static void regcomp_start(char_u *expr, int flags);
static char_u *reg(int, int *);
static char_u *regbranch(int *flagp);
static char_u *regconcat(int *flagp);
static char_u *regpiece(int *);
static char_u *regatom(int *);
static char_u *regnode(int);
static int use_multibytecode(int c);
static int prog_magic_wrong(void);
static char_u *regnext(char_u *);
static void regc(int b);
static void regmbc(int c);
#define REGMBC(x) regmbc(x);
#define CASEMBC(x) case x:
static void reginsert(int, char_u *);
static void reginsert_nr(int op, long val, char_u *opnd);
static void reginsert_limits(int, long, long, char_u *);
static char_u *re_put_long(char_u *pr, long_u val);
static int read_limits(long *, long *);
static void regtail(char_u *, char_u *);
static void regoptail(char_u *, char_u *);
static int reg_iswordc(int);

static regengine_T bt_regengine;
static regengine_T nfa_regengine;

/*
 * Return TRUE if compiled regular expression "prog" can match a line break.
 */
int re_multiline(regprog_T *prog)
{
  return (prog->regflags & RF_HASNL);
}

/*
 * Check for an equivalence class name "[=a=]".  "pp" points to the '['.
 * Returns a character representing the class. Zero means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
static int
get_equi_class(char_u **pp)
{
  int c;
  int l = 1;
  char_u *p = *pp;

  if (p[1] == '=' && p[2] != NUL)
  {
    if (has_mbyte)
      l = (*mb_ptr2len)(p + 2);
    if (p[l + 2] == '=' && p[l + 3] == ']')
    {
      if (has_mbyte)
        c = mb_ptr2char(p + 2);
      else
        c = p[2];
      *pp += l + 4;
      return c;
    }
  }
  return 0;
}

#ifdef EBCDIC
/*
 * Table for equivalence class "c". (IBM-1047)
 */
char *EQUIVAL_CLASS_C[16] = {
    "A\x62\x63\x64\x65\x66\x67",
    "C\x68",
    "E\x71\x72\x73\x74",
    "I\x75\x76\x77\x78",
    "N\x69",
    "O\xEB\xEC\xED\xEE\xEF\x80",
    "U\xFB\xFC\xFD\xFE",
    "Y\xBA",
    "a\x42\x43\x44\x45\x46\x47",
    "c\x48",
    "e\x51\x52\x53\x54",
    "i\x55\x56\x57\x58",
    "n\x49",
    "o\xCB\xCC\xCD\xCE\xCF\x70",
    "u\xDB\xDC\xDD\xDE",
    "y\x8D\xDF",
};
#endif

/*
 * Produce the bytes for equivalence class "c".
 * Currently only handles latin1, latin9 and utf-8.
 * NOTE: When changing this function, also change nfa_emit_equi_class()
 */
static void
reg_equi_class(int c)
{
  if (enc_utf8 || STRCMP(p_enc, "latin1") == 0 || STRCMP(p_enc, "iso-8859-15") == 0)
  {
#ifdef EBCDIC
    int i;

    /* This might be slower than switch/case below. */
    for (i = 0; i < 16; i++)
    {
      if (vim_strchr(EQUIVAL_CLASS_C[i], c) != NULL)
      {
        char *p = EQUIVAL_CLASS_C[i];

        while (*p != 0)
          regmbc(*p++);
        return;
      }
    }
#else
    switch (c)
    {
    /* Do not use '\300' style, it results in a negative number. */
    case 'A':
    case 0xc0:
    case 0xc1:
    case 0xc2:
    case 0xc3:
    case 0xc4:
    case 0xc5:
      CASEMBC(0x100)
      CASEMBC(0x102)
      CASEMBC(0x104)
      CASEMBC(0x1cd)
      CASEMBC(0x1de)
      CASEMBC(0x1e0)
      CASEMBC(0x1ea2)
      regmbc('A');
      regmbc(0xc0);
      regmbc(0xc1);
      regmbc(0xc2);
      regmbc(0xc3);
      regmbc(0xc4);
      regmbc(0xc5);
      REGMBC(0x100)
      REGMBC(0x102)
      REGMBC(0x104)
      REGMBC(0x1cd)
      REGMBC(0x1de)
      REGMBC(0x1e0)
      REGMBC(0x1ea2)
      return;
    case 'B':
      CASEMBC(0x1e02)
      CASEMBC(0x1e06)
      regmbc('B');
      REGMBC(0x1e02)
      REGMBC(0x1e06)
      return;
    case 'C':
    case 0xc7:
      CASEMBC(0x106)
      CASEMBC(0x108)
      CASEMBC(0x10a)
      CASEMBC(0x10c)
      regmbc('C');
      regmbc(0xc7);
      REGMBC(0x106)
      REGMBC(0x108)
      REGMBC(0x10a)
      REGMBC(0x10c)
      return;
    case 'D':
      CASEMBC(0x10e)
      CASEMBC(0x110)
      CASEMBC(0x1e0a)
      CASEMBC(0x1e0e)
      CASEMBC(0x1e10)
      regmbc('D');
      REGMBC(0x10e)
      REGMBC(0x110)
      REGMBC(0x1e0a)
      REGMBC(0x1e0e)
      REGMBC(0x1e10)
      return;
    case 'E':
    case 0xc8:
    case 0xc9:
    case 0xca:
    case 0xcb:
      CASEMBC(0x112)
      CASEMBC(0x114)
      CASEMBC(0x116)
      CASEMBC(0x118)
      CASEMBC(0x11a)
      CASEMBC(0x1eba)
      CASEMBC(0x1ebc)
      regmbc('E');
      regmbc(0xc8);
      regmbc(0xc9);
      regmbc(0xca);
      regmbc(0xcb);
      REGMBC(0x112)
      REGMBC(0x114)
      REGMBC(0x116)
      REGMBC(0x118)
      REGMBC(0x11a)
      REGMBC(0x1eba)
      REGMBC(0x1ebc)
      return;
    case 'F':
      CASEMBC(0x1e1e)
      regmbc('F');
      REGMBC(0x1e1e)
      return;
    case 'G':
      CASEMBC(0x11c)
      CASEMBC(0x11e)
      CASEMBC(0x120)
      CASEMBC(0x122)
      CASEMBC(0x1e4)
      CASEMBC(0x1e6)
      CASEMBC(0x1f4)
      CASEMBC(0x1e20)
      regmbc('G');
      REGMBC(0x11c)
      REGMBC(0x11e)
      REGMBC(0x120)
      REGMBC(0x122)
      REGMBC(0x1e4)
      REGMBC(0x1e6)
      REGMBC(0x1f4)
      REGMBC(0x1e20)
      return;
    case 'H':
      CASEMBC(0x124)
      CASEMBC(0x126)
      CASEMBC(0x1e22)
      CASEMBC(0x1e26)
      CASEMBC(0x1e28)
      regmbc('H');
      REGMBC(0x124)
      REGMBC(0x126)
      REGMBC(0x1e22)
      REGMBC(0x1e26)
      REGMBC(0x1e28)
      return;
    case 'I':
    case 0xcc:
    case 0xcd:
    case 0xce:
    case 0xcf:
      CASEMBC(0x128)
      CASEMBC(0x12a)
      CASEMBC(0x12c)
      CASEMBC(0x12e)
      CASEMBC(0x130)
      CASEMBC(0x1cf)
      CASEMBC(0x1ec8)
      regmbc('I');
      regmbc(0xcc);
      regmbc(0xcd);
      regmbc(0xce);
      regmbc(0xcf);
      REGMBC(0x128)
      REGMBC(0x12a)
      REGMBC(0x12c)
      REGMBC(0x12e)
      REGMBC(0x130)
      REGMBC(0x1cf)
      REGMBC(0x1ec8)
      return;
    case 'J':
      CASEMBC(0x134)
      regmbc('J');
      REGMBC(0x134)
      return;
    case 'K':
      CASEMBC(0x136)
      CASEMBC(0x1e8)
      CASEMBC(0x1e30)
      CASEMBC(0x1e34)
      regmbc('K');
      REGMBC(0x136)
      REGMBC(0x1e8)
      REGMBC(0x1e30)
      REGMBC(0x1e34)
      return;
    case 'L':
      CASEMBC(0x139)
      CASEMBC(0x13b)
      CASEMBC(0x13d)
      CASEMBC(0x13f)
      CASEMBC(0x141)
      CASEMBC(0x1e3a)
      regmbc('L');
      REGMBC(0x139)
      REGMBC(0x13b)
      REGMBC(0x13d)
      REGMBC(0x13f)
      REGMBC(0x141)
      REGMBC(0x1e3a)
      return;
    case 'M':
      CASEMBC(0x1e3e)
      CASEMBC(0x1e40)
      regmbc('M');
      REGMBC(0x1e3e)
      REGMBC(0x1e40)
      return;
    case 'N':
    case 0xd1:
      CASEMBC(0x143)
      CASEMBC(0x145)
      CASEMBC(0x147)
      CASEMBC(0x1e44)
      CASEMBC(0x1e48)
      regmbc('N');
      regmbc(0xd1);
      REGMBC(0x143)
      REGMBC(0x145)
      REGMBC(0x147)
      REGMBC(0x1e44)
      REGMBC(0x1e48)
      return;
    case 'O':
    case 0xd2:
    case 0xd3:
    case 0xd4:
    case 0xd5:
    case 0xd6:
    case 0xd8:
      CASEMBC(0x14c)
      CASEMBC(0x14e)
      CASEMBC(0x150)
      CASEMBC(0x1a0)
      CASEMBC(0x1d1)
      CASEMBC(0x1ea)
      CASEMBC(0x1ec)
      CASEMBC(0x1ece)
      regmbc('O');
      regmbc(0xd2);
      regmbc(0xd3);
      regmbc(0xd4);
      regmbc(0xd5);
      regmbc(0xd6);
      regmbc(0xd8);
      REGMBC(0x14c)
      REGMBC(0x14e)
      REGMBC(0x150)
      REGMBC(0x1a0)
      REGMBC(0x1d1)
      REGMBC(0x1ea)
      REGMBC(0x1ec)
      REGMBC(0x1ece)
      return;
    case 'P':
    case 0x1e54:
    case 0x1e56:
      regmbc('P');
      REGMBC(0x1e54)
      REGMBC(0x1e56)
      return;
    case 'R':
      CASEMBC(0x154)
      CASEMBC(0x156)
      CASEMBC(0x158)
      CASEMBC(0x1e58)
      CASEMBC(0x1e5e)
      regmbc('R');
      REGMBC(0x154)
      REGMBC(0x156)
      REGMBC(0x158)
      REGMBC(0x1e58)
      REGMBC(0x1e5e)
      return;
    case 'S':
      CASEMBC(0x15a)
      CASEMBC(0x15c)
      CASEMBC(0x15e)
      CASEMBC(0x160)
      CASEMBC(0x1e60)
      regmbc('S');
      REGMBC(0x15a)
      REGMBC(0x15c)
      REGMBC(0x15e)
      REGMBC(0x160)
      REGMBC(0x1e60)
      return;
    case 'T':
      CASEMBC(0x162)
      CASEMBC(0x164)
      CASEMBC(0x166)
      CASEMBC(0x1e6a)
      CASEMBC(0x1e6e)
      regmbc('T');
      REGMBC(0x162)
      REGMBC(0x164)
      REGMBC(0x166)
      REGMBC(0x1e6a)
      REGMBC(0x1e6e)
      return;
    case 'U':
    case 0xd9:
    case 0xda:
    case 0xdb:
    case 0xdc:
      CASEMBC(0x168)
      CASEMBC(0x16a)
      CASEMBC(0x16c)
      CASEMBC(0x16e)
      CASEMBC(0x170)
      CASEMBC(0x172)
      CASEMBC(0x1af)
      CASEMBC(0x1d3)
      CASEMBC(0x1ee6)
      regmbc('U');
      regmbc(0xd9);
      regmbc(0xda);
      regmbc(0xdb);
      regmbc(0xdc);
      REGMBC(0x168)
      REGMBC(0x16a)
      REGMBC(0x16c)
      REGMBC(0x16e)
      REGMBC(0x170)
      REGMBC(0x172)
      REGMBC(0x1af)
      REGMBC(0x1d3)
      REGMBC(0x1ee6)
      return;
    case 'V':
      CASEMBC(0x1e7c)
      regmbc('V');
      REGMBC(0x1e7c)
      return;
    case 'W':
      CASEMBC(0x174)
      CASEMBC(0x1e80)
      CASEMBC(0x1e82)
      CASEMBC(0x1e84)
      CASEMBC(0x1e86)
      regmbc('W');
      REGMBC(0x174)
      REGMBC(0x1e80)
      REGMBC(0x1e82)
      REGMBC(0x1e84)
      REGMBC(0x1e86)
      return;
    case 'X':
      CASEMBC(0x1e8a)
      CASEMBC(0x1e8c)
      regmbc('X');
      REGMBC(0x1e8a)
      REGMBC(0x1e8c)
      return;
    case 'Y':
    case 0xdd:
      CASEMBC(0x176)
      CASEMBC(0x178)
      CASEMBC(0x1e8e)
      CASEMBC(0x1ef2)
      CASEMBC(0x1ef6)
      CASEMBC(0x1ef8)
      regmbc('Y');
      regmbc(0xdd);
      REGMBC(0x176)
      REGMBC(0x178)
      REGMBC(0x1e8e)
      REGMBC(0x1ef2)
      REGMBC(0x1ef6)
      REGMBC(0x1ef8)
      return;
    case 'Z':
      CASEMBC(0x179)
      CASEMBC(0x17b)
      CASEMBC(0x17d)
      CASEMBC(0x1b5)
      CASEMBC(0x1e90)
      CASEMBC(0x1e94)
      regmbc('Z');
      REGMBC(0x179)
      REGMBC(0x17b)
      REGMBC(0x17d)
      REGMBC(0x1b5)
      REGMBC(0x1e90)
      REGMBC(0x1e94)
      return;
    case 'a':
    case 0xe0:
    case 0xe1:
    case 0xe2:
    case 0xe3:
    case 0xe4:
    case 0xe5:
      CASEMBC(0x101)
      CASEMBC(0x103)
      CASEMBC(0x105)
      CASEMBC(0x1ce)
      CASEMBC(0x1df)
      CASEMBC(0x1e1)
      CASEMBC(0x1ea3)
      regmbc('a');
      regmbc(0xe0);
      regmbc(0xe1);
      regmbc(0xe2);
      regmbc(0xe3);
      regmbc(0xe4);
      regmbc(0xe5);
      REGMBC(0x101)
      REGMBC(0x103)
      REGMBC(0x105)
      REGMBC(0x1ce)
      REGMBC(0x1df)
      REGMBC(0x1e1)
      REGMBC(0x1ea3)
      return;
    case 'b':
      CASEMBC(0x1e03)
      CASEMBC(0x1e07)
      regmbc('b');
      REGMBC(0x1e03)
      REGMBC(0x1e07)
      return;
    case 'c':
    case 0xe7:
      CASEMBC(0x107)
      CASEMBC(0x109)
      CASEMBC(0x10b)
      CASEMBC(0x10d)
      regmbc('c');
      regmbc(0xe7);
      REGMBC(0x107)
      REGMBC(0x109)
      REGMBC(0x10b)
      REGMBC(0x10d)
      return;
    case 'd':
      CASEMBC(0x10f)
      CASEMBC(0x111)
      CASEMBC(0x1e0b)
      CASEMBC(0x1e0f)
      CASEMBC(0x1e11)
      regmbc('d');
      REGMBC(0x10f)
      REGMBC(0x111)
      REGMBC(0x1e0b)
      REGMBC(0x1e0f)
      REGMBC(0x1e11)
      return;
    case 'e':
    case 0xe8:
    case 0xe9:
    case 0xea:
    case 0xeb:
      CASEMBC(0x113)
      CASEMBC(0x115)
      CASEMBC(0x117)
      CASEMBC(0x119)
      CASEMBC(0x11b)
      CASEMBC(0x1ebb)
      CASEMBC(0x1ebd)
      regmbc('e');
      regmbc(0xe8);
      regmbc(0xe9);
      regmbc(0xea);
      regmbc(0xeb);
      REGMBC(0x113)
      REGMBC(0x115)
      REGMBC(0x117)
      REGMBC(0x119)
      REGMBC(0x11b)
      REGMBC(0x1ebb)
      REGMBC(0x1ebd)
      return;
    case 'f':
      CASEMBC(0x1e1f)
      regmbc('f');
      REGMBC(0x1e1f)
      return;
    case 'g':
      CASEMBC(0x11d)
      CASEMBC(0x11f)
      CASEMBC(0x121)
      CASEMBC(0x123)
      CASEMBC(0x1e5)
      CASEMBC(0x1e7)
      CASEMBC(0x1f5)
      CASEMBC(0x1e21)
      regmbc('g');
      REGMBC(0x11d)
      REGMBC(0x11f)
      REGMBC(0x121)
      REGMBC(0x123)
      REGMBC(0x1e5)
      REGMBC(0x1e7)
      REGMBC(0x1f5)
      REGMBC(0x1e21)
      return;
    case 'h':
      CASEMBC(0x125)
      CASEMBC(0x127)
      CASEMBC(0x1e23)
      CASEMBC(0x1e27)
      CASEMBC(0x1e29)
      CASEMBC(0x1e96)
      regmbc('h');
      REGMBC(0x125)
      REGMBC(0x127)
      REGMBC(0x1e23)
      REGMBC(0x1e27)
      REGMBC(0x1e29)
      REGMBC(0x1e96)
      return;
    case 'i':
    case 0xec:
    case 0xed:
    case 0xee:
    case 0xef:
      CASEMBC(0x129)
      CASEMBC(0x12b)
      CASEMBC(0x12d)
      CASEMBC(0x12f)
      CASEMBC(0x1d0)
      CASEMBC(0x1ec9)
      regmbc('i');
      regmbc(0xec);
      regmbc(0xed);
      regmbc(0xee);
      regmbc(0xef);
      REGMBC(0x129)
      REGMBC(0x12b)
      REGMBC(0x12d)
      REGMBC(0x12f)
      REGMBC(0x1d0)
      REGMBC(0x1ec9)
      return;
    case 'j':
      CASEMBC(0x135)
      CASEMBC(0x1f0)
      regmbc('j');
      REGMBC(0x135)
      REGMBC(0x1f0)
      return;
    case 'k':
      CASEMBC(0x137)
      CASEMBC(0x1e9)
      CASEMBC(0x1e31)
      CASEMBC(0x1e35)
      regmbc('k');
      REGMBC(0x137)
      REGMBC(0x1e9)
      REGMBC(0x1e31)
      REGMBC(0x1e35)
      return;
    case 'l':
      CASEMBC(0x13a)
      CASEMBC(0x13c)
      CASEMBC(0x13e)
      CASEMBC(0x140)
      CASEMBC(0x142)
      CASEMBC(0x1e3b)
      regmbc('l');
      REGMBC(0x13a)
      REGMBC(0x13c)
      REGMBC(0x13e)
      REGMBC(0x140)
      REGMBC(0x142)
      REGMBC(0x1e3b)
      return;
    case 'm':
      CASEMBC(0x1e3f)
      CASEMBC(0x1e41)
      regmbc('m');
      REGMBC(0x1e3f)
      REGMBC(0x1e41)
      return;
    case 'n':
    case 0xf1:
      CASEMBC(0x144)
      CASEMBC(0x146)
      CASEMBC(0x148)
      CASEMBC(0x149)
      CASEMBC(0x1e45)
      CASEMBC(0x1e49)
      regmbc('n');
      regmbc(0xf1);
      REGMBC(0x144)
      REGMBC(0x146)
      REGMBC(0x148)
      REGMBC(0x149)
      REGMBC(0x1e45)
      REGMBC(0x1e49)
      return;
    case 'o':
    case 0xf2:
    case 0xf3:
    case 0xf4:
    case 0xf5:
    case 0xf6:
    case 0xf8:
      CASEMBC(0x14d)
      CASEMBC(0x14f)
      CASEMBC(0x151)
      CASEMBC(0x1a1)
      CASEMBC(0x1d2)
      CASEMBC(0x1eb)
      CASEMBC(0x1ed)
      CASEMBC(0x1ecf)
      regmbc('o');
      regmbc(0xf2);
      regmbc(0xf3);
      regmbc(0xf4);
      regmbc(0xf5);
      regmbc(0xf6);
      regmbc(0xf8);
      REGMBC(0x14d)
      REGMBC(0x14f)
      REGMBC(0x151)
      REGMBC(0x1a1)
      REGMBC(0x1d2)
      REGMBC(0x1eb)
      REGMBC(0x1ed)
      REGMBC(0x1ecf)
      return;
    case 'p':
      CASEMBC(0x1e55)
      CASEMBC(0x1e57)
      regmbc('p');
      REGMBC(0x1e55)
      REGMBC(0x1e57)
      return;
    case 'r':
      CASEMBC(0x155)
      CASEMBC(0x157)
      CASEMBC(0x159)
      CASEMBC(0x1e59)
      CASEMBC(0x1e5f)
      regmbc('r');
      REGMBC(0x155)
      REGMBC(0x157)
      REGMBC(0x159)
      REGMBC(0x1e59)
      REGMBC(0x1e5f)
      return;
    case 's':
      CASEMBC(0x15b)
      CASEMBC(0x15d)
      CASEMBC(0x15f)
      CASEMBC(0x161)
      CASEMBC(0x1e61)
      regmbc('s');
      REGMBC(0x15b)
      REGMBC(0x15d)
      REGMBC(0x15f)
      REGMBC(0x161)
      REGMBC(0x1e61)
      return;
    case 't':
      CASEMBC(0x163)
      CASEMBC(0x165)
      CASEMBC(0x167)
      CASEMBC(0x1e6b)
      CASEMBC(0x1e6f)
      CASEMBC(0x1e97)
      regmbc('t');
      REGMBC(0x163)
      REGMBC(0x165)
      REGMBC(0x167)
      REGMBC(0x1e6b)
      REGMBC(0x1e6f)
      REGMBC(0x1e97)
      return;
    case 'u':
    case 0xf9:
    case 0xfa:
    case 0xfb:
    case 0xfc:
      CASEMBC(0x169)
      CASEMBC(0x16b)
      CASEMBC(0x16d)
      CASEMBC(0x16f)
      CASEMBC(0x171)
      CASEMBC(0x173)
      CASEMBC(0x1b0)
      CASEMBC(0x1d4)
      CASEMBC(0x1ee7)
      regmbc('u');
      regmbc(0xf9);
      regmbc(0xfa);
      regmbc(0xfb);
      regmbc(0xfc);
      REGMBC(0x169)
      REGMBC(0x16b)
      REGMBC(0x16d)
      REGMBC(0x16f)
      REGMBC(0x171)
      REGMBC(0x173)
      REGMBC(0x1b0)
      REGMBC(0x1d4)
      REGMBC(0x1ee7)
      return;
    case 'v':
      CASEMBC(0x1e7d)
      regmbc('v');
      REGMBC(0x1e7d)
      return;
    case 'w':
      CASEMBC(0x175)
      CASEMBC(0x1e81)
      CASEMBC(0x1e83)
      CASEMBC(0x1e85)
      CASEMBC(0x1e87)
      CASEMBC(0x1e98)
      regmbc('w');
      REGMBC(0x175)
      REGMBC(0x1e81)
      REGMBC(0x1e83)
      REGMBC(0x1e85)
      REGMBC(0x1e87)
      REGMBC(0x1e98)
      return;
    case 'x':
      CASEMBC(0x1e8b)
      CASEMBC(0x1e8d)
      regmbc('x');
      REGMBC(0x1e8b)
      REGMBC(0x1e8d)
      return;
    case 'y':
    case 0xfd:
    case 0xff:
      CASEMBC(0x177)
      CASEMBC(0x1e8f)
      CASEMBC(0x1e99)
      CASEMBC(0x1ef3)
      CASEMBC(0x1ef7)
      CASEMBC(0x1ef9)
      regmbc('y');
      regmbc(0xfd);
      regmbc(0xff);
      REGMBC(0x177)
      REGMBC(0x1e8f)
      REGMBC(0x1e99)
      REGMBC(0x1ef3)
      REGMBC(0x1ef7)
      REGMBC(0x1ef9)
      return;
    case 'z':
      CASEMBC(0x17a)
      CASEMBC(0x17c)
      CASEMBC(0x17e)
      CASEMBC(0x1b6)
      CASEMBC(0x1e91)
      CASEMBC(0x1e95)
      regmbc('z');
      REGMBC(0x17a)
      REGMBC(0x17c)
      REGMBC(0x17e)
      REGMBC(0x1b6)
      REGMBC(0x1e91)
      REGMBC(0x1e95)
      return;
    }
#endif
  }
  regmbc(c);
}

/*
 * Check for a collating element "[.a.]".  "pp" points to the '['.
 * Returns a character. Zero means that no item was recognized.  Otherwise
 * "pp" is advanced to after the item.
 * Currently only single characters are recognized!
 */
static int
get_coll_element(char_u **pp)
{
  int c;
  int l = 1;
  char_u *p = *pp;

  if (p[0] != NUL && p[1] == '.' && p[2] != NUL)
  {
    if (has_mbyte)
      l = (*mb_ptr2len)(p + 2);
    if (p[l + 2] == '.' && p[l + 3] == ']')
    {
      if (has_mbyte)
        c = mb_ptr2char(p + 2);
      else
        c = p[2];
      *pp += l + 4;
      return c;
    }
  }
  return 0;
}

static int reg_cpo_lit; /* 'cpoptions' contains 'l' flag */
static int reg_cpo_bsl; /* 'cpoptions' contains '\' flag */

static void
get_cpo_flags(void)
{
  reg_cpo_lit = vim_strchr(p_cpo, CPO_LITERAL) != NULL;
  reg_cpo_bsl = vim_strchr(p_cpo, CPO_BACKSL) != NULL;
}

/*
 * Skip over a "[]" range.
 * "p" must point to the character after the '['.
 * The returned pointer is on the matching ']', or the terminating NUL.
 */
static char_u *
skip_anyof(char_u *p)
{
  int l;

  if (*p == '^') /* Complement of range. */
    ++p;
  if (*p == ']' || *p == '-')
    ++p;
  while (*p != NUL && *p != ']')
  {
    if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1)
      p += l;
    else if (*p == '-')
    {
      ++p;
      if (*p != ']' && *p != NUL)
        MB_PTR_ADV(p);
    }
    else if (*p == '\\' && !reg_cpo_bsl && (vim_strchr(REGEXP_INRANGE, p[1]) != NULL || (!reg_cpo_lit && vim_strchr(REGEXP_ABBR, p[1]) != NULL)))
      p += 2;
    else if (*p == '[')
    {
      if (get_char_class(&p) == CLASS_NONE && get_equi_class(&p) == 0 && get_coll_element(&p) == 0 && *p != NUL)
        ++p; /* it is not a class name and not NUL */
    }
    else
      ++p;
  }

  return p;
}

/*
 * Skip past regular expression.
 * Stop at end of "startp" or where "dirc" is found ('/', '?', etc).
 * Take care of characters with a backslash in front of it.
 * Skip strings inside [ and ].
 * When "newp" is not NULL and "dirc" is '?', make an allocated copy of the
 * expression and change "\?" to "?".  If "*newp" is not NULL the expression
 * is changed in-place.
 */
char_u *
skip_regexp(
    char_u *startp,
    int dirc,
    int magic,
    char_u **newp)
{
  int mymagic;
  char_u *p = startp;

  if (magic)
    mymagic = MAGIC_ON;
  else
    mymagic = MAGIC_OFF;
  get_cpo_flags();

  for (; p[0] != NUL; MB_PTR_ADV(p))
  {
    if (p[0] == dirc) /* found end of regexp */
      break;
    if ((p[0] == '[' && mymagic >= MAGIC_ON) || (p[0] == '\\' && p[1] == '[' && mymagic <= MAGIC_OFF))
    {
      p = skip_anyof(p + 1);
      if (p[0] == NUL)
        break;
    }
    else if (p[0] == '\\' && p[1] != NUL)
    {
      if (dirc == '?' && newp != NULL && p[1] == '?')
      {
        /* change "\?" to "?", make a copy first. */
        if (*newp == NULL)
        {
          *newp = vim_strsave(startp);
          if (*newp != NULL)
            p = *newp + (p - startp);
        }
        if (*newp != NULL)
          STRMOVE(p, p + 1);
        else
          ++p;
      }
      else
        ++p; /* skip next character */
      if (*p == 'v')
        mymagic = MAGIC_ALL;
      else if (*p == 'V')
        mymagic = MAGIC_NONE;
    }
  }
  return p;
}

/*
 * Return TRUE if the back reference is legal. We must have seen the close
 * brace.
 * TODO: Should also check that we don't refer to something that is repeated
 * (+*=): what instance of the repetition should we match?
 */
static int
seen_endbrace(int refnum)
{
  if (!had_endbrace[refnum])
  {
    char_u *p;

    /* Trick: check if "@<=" or "@<!" follows, in which case
	 * the \1 can appear before the referenced match. */
    for (p = regparse; *p != NUL; ++p)
      if (p[0] == '@' && p[1] == '<' && (p[2] == '!' || p[2] == '='))
        break;
    if (*p == NUL)
    {
      emsg(_("E65: Illegal back reference"));
      rc_did_emsg = TRUE;
      return FALSE;
    }
  }
  return TRUE;
}

/*
 * bt_regcomp() - compile a regular expression into internal code for the
 * traditional back track matcher.
 * Returns the program in allocated space.  Returns NULL for an error.
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because vim_free() must be able to free it all.)
 *
 * Whether upper/lower case is to be ignored is decided when executing the
 * program, it does not matter here.
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.
 * "re_flags": RE_MAGIC and/or RE_STRING.
 */
static regprog_T *
bt_regcomp(char_u *expr, int re_flags)
{
  bt_regprog_T *r;
  char_u *scan;
  char_u *longest;
  int len;
  int flags;

  if (expr == NULL)
    EMSG_RET_NULL(_(e_null));

  init_class_tab();

  /*
     * First pass: determine size, legality.
     */
  regcomp_start(expr, re_flags);
  regcode = JUST_CALC_SIZE;
  regc(REGMAGIC);
  if (reg(REG_NOPAREN, &flags) == NULL)
    return NULL;

  /* Allocate space. */
  r = alloc(sizeof(bt_regprog_T) + regsize);
  if (r == NULL)
    return NULL;
  r->re_in_use = FALSE;

  /*
     * Second pass: emit code.
     */
  regcomp_start(expr, re_flags);
  regcode = r->program;
  regc(REGMAGIC);
  if (reg(REG_NOPAREN, &flags) == NULL || reg_toolong)
  {
    vim_free(r);
    if (reg_toolong)
      EMSG_RET_NULL(_("E339: Pattern too long"));
    return NULL;
  }

  /* Dig out information for optimizations. */
  r->regstart = NUL; /* Worst-case defaults. */
  r->reganch = 0;
  r->regmust = NULL;
  r->regmlen = 0;
  r->regflags = regflags;
  if (flags & HASNL)
    r->regflags |= RF_HASNL;
  if (flags & HASLOOKBH)
    r->regflags |= RF_LOOKBH;
  scan = r->program + 1;        /* First BRANCH. */
  if (OP(regnext(scan)) == END) /* Only one top-level choice. */
  {
    scan = OPERAND(scan);

    /* Starting-point info. */
    if (OP(scan) == BOL || OP(scan) == RE_BOF)
    {
      r->reganch++;
      scan = regnext(scan);
    }

    if (OP(scan) == EXACTLY)
    {
      if (has_mbyte)
        r->regstart = (*mb_ptr2char)(OPERAND(scan));
      else
        r->regstart = *OPERAND(scan);
    }
    else if ((OP(scan) == BOW || OP(scan) == EOW || OP(scan) == NOTHING || OP(scan) == MOPEN + 0 || OP(scan) == NOPEN || OP(scan) == MCLOSE + 0 || OP(scan) == NCLOSE) && OP(regnext(scan)) == EXACTLY)
    {
      if (has_mbyte)
        r->regstart = (*mb_ptr2char)(OPERAND(regnext(scan)));
      else
        r->regstart = *OPERAND(regnext(scan));
    }

    /*
	 * If there's something expensive in the r.e., find the longest
	 * literal string that must appear and make it the regmust.  Resolve
	 * ties in favor of later strings, since the regstart check works
	 * with the beginning of the r.e. and avoiding duplication
	 * strengthens checking.  Not a strong reason, but sufficient in the
	 * absence of others.
	 */
    /*
	 * When the r.e. starts with BOW, it is faster to look for a regmust
	 * first. Used a lot for "#" and "*" commands. (Added by mool).
	 */
    if ((flags & SPSTART || OP(scan) == BOW || OP(scan) == EOW) && !(flags & HASNL))
    {
      longest = NULL;
      len = 0;
      for (; scan != NULL; scan = regnext(scan))
        if (OP(scan) == EXACTLY && STRLEN(OPERAND(scan)) >= (size_t)len)
        {
          longest = OPERAND(scan);
          len = (int)STRLEN(OPERAND(scan));
        }
      r->regmust = longest;
      r->regmlen = len;
    }
  }
#ifdef BT_REGEXP_DUMP
  regdump(expr, r);
#endif
  r->engine = &bt_regengine;
  return (regprog_T *)r;
}

/*
 * Free a compiled regexp program, returned by bt_regcomp().
 */
static void
bt_regfree(regprog_T *prog)
{
  vim_free(prog);
}

/*
 * Setup to parse the regexp.  Used once to get the length and once to do it.
 */
static void
regcomp_start(
    char_u *expr,
    int re_flags) /* see vim_regcomp() */
{
  initchr(expr);
  if (re_flags & RE_MAGIC)
    reg_magic = MAGIC_ON;
  else
    reg_magic = MAGIC_OFF;
  reg_string = (re_flags & RE_STRING);
  reg_strict = (re_flags & RE_STRICT);
  get_cpo_flags();

  num_complex_braces = 0;
  regnpar = 1;
  vim_memset(had_endbrace, 0, sizeof(had_endbrace));
  regsize = 0L;
  reg_toolong = FALSE;
  regflags = 0;
}

// variables used for parsing
static int at_start;      // True when on the first character
static int prev_at_start; // True when on the second character

/*
 * Parse regular expression, i.e. main body or parenthesized thing.
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
static char_u *
reg(
    int paren, /* REG_NOPAREN, REG_PAREN, REG_NPAREN or REG_ZPAREN */
    int *flagp)
{
  char_u *ret;
  char_u *br;
  char_u *ender;
  int parno = 0;
  int flags;

  *flagp = HASWIDTH; /* Tentatively. */

  if (paren == REG_PAREN)
  {
    /* Make a MOPEN node. */
    if (regnpar >= NSUBEXP)
      EMSG2_RET_NULL(_("E51: Too many %s("), reg_magic == MAGIC_ALL);
    parno = regnpar;
    ++regnpar;
    ret = regnode(MOPEN + parno);
  }
  else if (paren == REG_NPAREN)
  {
    /* Make a NOPEN node. */
    ret = regnode(NOPEN);
  }
  else
    ret = NULL;

  /* Pick up the branches, linking them together. */
  br = regbranch(&flags);
  if (br == NULL)
    return NULL;
  if (ret != NULL)
    regtail(ret, br); /* [MZ]OPEN -> first. */
  else
    ret = br;
  /* If one of the branches can be zero-width, the whole thing can.
     * If one of the branches has * at start or matches a line-break, the
     * whole thing can. */
  if (!(flags & HASWIDTH))
    *flagp &= ~HASWIDTH;
  *flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
  while (peekchr() == Magic('|'))
  {
    skipchr();
    br = regbranch(&flags);
    if (br == NULL || reg_toolong)
      return NULL;
    regtail(ret, br); /* BRANCH -> BRANCH. */
    if (!(flags & HASWIDTH))
      *flagp &= ~HASWIDTH;
    *flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
  }

  /* Make a closing node, and hook it on the end. */
  ender = regnode(
      paren == REG_PAREN ? MCLOSE + parno : paren == REG_NPAREN ? NCLOSE : END);
  regtail(ret, ender);

  /* Hook the tails of the branches to the closing node. */
  for (br = ret; br != NULL; br = regnext(br))
    regoptail(br, ender);

  /* Check for proper termination. */
  if (paren != REG_NOPAREN && getchr() != Magic(')'))
  {
    if (paren == REG_NPAREN)
      EMSG2_RET_NULL(_(e_unmatchedpp), reg_magic == MAGIC_ALL);
    else
      EMSG2_RET_NULL(_(e_unmatchedp), reg_magic == MAGIC_ALL);
  }
  else if (paren == REG_NOPAREN && peekchr() != NUL)
  {
    if (curchr == Magic(')'))
      EMSG2_RET_NULL(_(e_unmatchedpar), reg_magic == MAGIC_ALL);
    else
      EMSG_RET_NULL(_(e_trailing)); /* "Can't happen". */
                                    /* NOTREACHED */
  }
  /*
     * Here we set the flag allowing back references to this set of
     * parentheses.
     */
  if (paren == REG_PAREN)
    had_endbrace[parno] = TRUE; /* have seen the close paren */
  return ret;
}

/*
 * Parse one alternative of an | operator.
 * Implements the & operator.
 */
static char_u *
regbranch(int *flagp)
{
  char_u *ret;
  char_u *chain = NULL;
  char_u *latest;
  int flags;

  *flagp = WORST | HASNL; /* Tentatively. */

  ret = regnode(BRANCH);
  for (;;)
  {
    latest = regconcat(&flags);
    if (latest == NULL)
      return NULL;
    /* If one of the branches has width, the whole thing has.  If one of
	 * the branches anchors at start-of-line, the whole thing does.
	 * If one of the branches uses look-behind, the whole thing does. */
    *flagp |= flags & (HASWIDTH | SPSTART | HASLOOKBH);
    /* If one of the branches doesn't match a line-break, the whole thing
	 * doesn't. */
    *flagp &= ~HASNL | (flags & HASNL);
    if (chain != NULL)
      regtail(chain, latest);
    if (peekchr() != Magic('&'))
      break;
    skipchr();
    regtail(latest, regnode(END)); /* operand ends */
    if (reg_toolong)
      break;
    reginsert(MATCH, latest);
    chain = latest;
  }

  return ret;
}

/*
 * Parse one alternative of an | or & operator.
 * Implements the concatenation operator.
 */
static char_u *
regconcat(int *flagp)
{
  char_u *first = NULL;
  char_u *chain = NULL;
  char_u *latest;
  int flags;
  int cont = TRUE;

  *flagp = WORST; /* Tentatively. */

  while (cont)
  {
    switch (peekchr())
    {
    case NUL:
    case Magic('|'):
    case Magic('&'):
    case Magic(')'):
      cont = FALSE;
      break;
    case Magic('Z'):
      regflags |= RF_ICOMBINE;
      skipchr_keepstart();
      break;
    case Magic('c'):
      regflags |= RF_ICASE;
      skipchr_keepstart();
      break;
    case Magic('C'):
      regflags |= RF_NOICASE;
      skipchr_keepstart();
      break;
    case Magic('v'):
      reg_magic = MAGIC_ALL;
      skipchr_keepstart();
      curchr = -1;
      break;
    case Magic('m'):
      reg_magic = MAGIC_ON;
      skipchr_keepstart();
      curchr = -1;
      break;
    case Magic('M'):
      reg_magic = MAGIC_OFF;
      skipchr_keepstart();
      curchr = -1;
      break;
    case Magic('V'):
      reg_magic = MAGIC_NONE;
      skipchr_keepstart();
      curchr = -1;
      break;
    default:
      latest = regpiece(&flags);
      if (latest == NULL || reg_toolong)
        return NULL;
      *flagp |= flags & (HASWIDTH | HASNL | HASLOOKBH);
      if (chain == NULL) /* First piece. */
        *flagp |= flags & SPSTART;
      else
        regtail(chain, latest);
      chain = latest;
      if (first == NULL)
        first = latest;
      break;
    }
  }
  if (first == NULL) /* Loop ran zero times. */
    first = regnode(NOTHING);
  return first;
}

/*
 * Parse something followed by possible [*+=].
 *
 * Note that the branching code sequences used for = and the general cases
 * of * and + are somewhat optimized:  they use the same NOTHING node as
 * both the endmarker for their branch list and the body of the last branch.
 * It might seem that this node could be dispensed with entirely, but the
 * endmarker role is not redundant.
 */
static char_u *
regpiece(int *flagp)
{
  char_u *ret;
  int op;
  char_u *next;
  int flags;
  long minval;
  long maxval;

  ret = regatom(&flags);
  if (ret == NULL)
    return NULL;

  op = peekchr();
  if (re_multi_type(op) == NOT_MULTI)
  {
    *flagp = flags;
    return ret;
  }
  /* default flags */
  *flagp = (WORST | SPSTART | (flags & (HASNL | HASLOOKBH)));

  skipchr();
  switch (op)
  {
  case Magic('*'):
    if (flags & SIMPLE)
      reginsert(STAR, ret);
    else
    {
      /* Emit x* as (x&|), where & means "self". */
      reginsert(BRANCH, ret);         /* Either x */
      regoptail(ret, regnode(BACK));  /* and loop */
      regoptail(ret, ret);            /* back */
      regtail(ret, regnode(BRANCH));  /* or */
      regtail(ret, regnode(NOTHING)); /* null. */
    }
    break;

  case Magic('+'):
    if (flags & SIMPLE)
      reginsert(PLUS, ret);
    else
    {
      /* Emit x+ as x(&|), where & means "self". */
      next = regnode(BRANCH); /* Either */
      regtail(ret, next);
      regtail(regnode(BACK), ret);    /* loop back */
      regtail(next, regnode(BRANCH)); /* or */
      regtail(ret, regnode(NOTHING)); /* null. */
    }
    *flagp = (WORST | HASWIDTH | (flags & (HASNL | HASLOOKBH)));
    break;

  case Magic('@'):
  {
    int lop = END;
    long nr;

    nr = getdecchrs();
    switch (no_Magic(getchr()))
    {
    case '=':
      lop = MATCH;
      break; /* \@= */
    case '!':
      lop = NOMATCH;
      break; /* \@! */
    case '>':
      lop = SUBPAT;
      break; /* \@> */
    case '<':
      switch (no_Magic(getchr()))
      {
      case '=':
        lop = BEHIND;
        break; /* \@<= */
      case '!':
        lop = NOBEHIND;
        break; /* \@<! */
      }
    }
    if (lop == END)
      EMSG2_RET_NULL(_("E59: invalid character after %s@"),
                     reg_magic == MAGIC_ALL);
    /* Look behind must match with behind_pos. */
    if (lop == BEHIND || lop == NOBEHIND)
    {
      regtail(ret, regnode(BHPOS));
      *flagp |= HASLOOKBH;
    }
    regtail(ret, regnode(END)); /* operand ends */
    if (lop == BEHIND || lop == NOBEHIND)
    {
      if (nr < 0)
        nr = 0; /* no limit is same as zero limit */
      reginsert_nr(lop, nr, ret);
    }
    else
      reginsert(lop, ret);
    break;
  }

  case Magic('?'):
  case Magic('='):
    /* Emit x= as (x|) */
    reginsert(BRANCH, ret);        /* Either x */
    regtail(ret, regnode(BRANCH)); /* or */
    next = regnode(NOTHING);       /* null. */
    regtail(ret, next);
    regoptail(ret, next);
    break;

  case Magic('{'):
    if (!read_limits(&minval, &maxval))
      return NULL;
    if (flags & SIMPLE)
    {
      reginsert(BRACE_SIMPLE, ret);
      reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
    }
    else
    {
      if (num_complex_braces >= 10)
        EMSG2_RET_NULL(_("E60: Too many complex %s{...}s"),
                       reg_magic == MAGIC_ALL);
      reginsert(BRACE_COMPLEX + num_complex_braces, ret);
      regoptail(ret, regnode(BACK));
      regoptail(ret, ret);
      reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
      ++num_complex_braces;
    }
    if (minval > 0 && maxval > 0)
      *flagp = (HASWIDTH | (flags & (HASNL | HASLOOKBH)));
    break;
  }
  if (re_multi_type(peekchr()) != NOT_MULTI)
  {
    // Can't have a multi follow a multi.
    if (peekchr() == Magic('*'))
      EMSG2_RET_NULL(_("E61: Nested %s*"), reg_magic >= MAGIC_ON);
    EMSG3_RET_NULL(_("E62: Nested %s%c"), reg_magic == MAGIC_ALL,
                   no_Magic(peekchr()));
  }

  return ret;
}

/* When making changes to classchars also change nfa_classcodes. */
static char_u *classchars = (char_u *)".iIkKfFpPsSdDxXoOwWhHaAlLuU";
static int classcodes[] = {
    ANY, IDENT, SIDENT, KWORD, SKWORD,
    FNAME, SFNAME, PRINT, SPRINT,
    WHITE, NWHITE, DIGIT, NDIGIT,
    HEX, NHEX, OCTAL, NOCTAL,
    WORD, NWORD, HEAD, NHEAD,
    ALPHA, NALPHA, LOWER, NLOWER,
    UPPER, NUPPER};

/*
 * Parse the lowest level.
 *
 * Optimization:  gobbles an entire sequence of ordinary characters so that
 * it can turn them into a single node, which is smaller to store and
 * faster to run.  Don't do this when one_exactly is set.
 */
static char_u *
regatom(int *flagp)
{
  char_u *ret;
  int flags;
  int c;
  char_u *p;
  int extra = 0;
  int save_prev_at_start = prev_at_start;

  *flagp = WORST; /* Tentatively. */

  c = getchr();
  switch (c)
  {
  case Magic('^'):
    ret = regnode(BOL);
    break;

  case Magic('$'):
    ret = regnode(EOL);
    break;

  case Magic('<'):
    ret = regnode(BOW);
    break;

  case Magic('>'):
    ret = regnode(EOW);
    break;

  case Magic('_'):
    c = no_Magic(getchr());
    if (c == '^') /* "\_^" is start-of-line */
    {
      ret = regnode(BOL);
      break;
    }
    if (c == '$') /* "\_$" is end-of-line */
    {
      ret = regnode(EOL);
      break;
    }

    extra = ADD_NL;
    *flagp |= HASNL;

    /* "\_[" is character range plus newline */
    if (c == '[')
      goto collection;

    /* "\_x" is character class plus newline */
    /* FALLTHROUGH */

    /*
	 * Character classes.
	 */
  case Magic('.'):
  case Magic('i'):
  case Magic('I'):
  case Magic('k'):
  case Magic('K'):
  case Magic('f'):
  case Magic('F'):
  case Magic('p'):
  case Magic('P'):
  case Magic('s'):
  case Magic('S'):
  case Magic('d'):
  case Magic('D'):
  case Magic('x'):
  case Magic('X'):
  case Magic('o'):
  case Magic('O'):
  case Magic('w'):
  case Magic('W'):
  case Magic('h'):
  case Magic('H'):
  case Magic('a'):
  case Magic('A'):
  case Magic('l'):
  case Magic('L'):
  case Magic('u'):
  case Magic('U'):
    p = vim_strchr(classchars, no_Magic(c));
    if (p == NULL)
      EMSG_RET_NULL(_("E63: invalid use of \\_"));

    /* When '.' is followed by a composing char ignore the dot, so that
	 * the composing char is matched here. */
    if (enc_utf8 && c == Magic('.') && utf_iscomposing(peekchr()))
    {
      c = getchr();
      goto do_multibyte;
    }
    ret = regnode(classcodes[p - classchars] + extra);
    *flagp |= HASWIDTH | SIMPLE;
    break;

  case Magic('n'):
    if (reg_string)
    {
      /* In a string "\n" matches a newline character. */
      ret = regnode(EXACTLY);
      regc(NL);
      regc(NUL);
      *flagp |= HASWIDTH | SIMPLE;
    }
    else
    {
      /* In buffer text "\n" matches the end of a line. */
      ret = regnode(NEWL);
      *flagp |= HASWIDTH | HASNL;
    }
    break;

  case Magic('('):
    if (one_exactly)
      EMSG_ONE_RET_NULL;
    ret = reg(REG_PAREN, &flags);
    if (ret == NULL)
      return NULL;
    *flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
    break;

  case NUL:
  case Magic('|'):
  case Magic('&'):
  case Magic(')'):
    if (one_exactly)
      EMSG_ONE_RET_NULL;
    IEMSG_RET_NULL(_(e_internal)); /* Supposed to be caught earlier. */
                                   /* NOTREACHED */

  case Magic('='):
  case Magic('?'):
  case Magic('+'):
  case Magic('@'):
  case Magic('{'):
  case Magic('*'):
    c = no_Magic(c);
    EMSG3_RET_NULL(_("E64: %s%c follows nothing"),
                   (c == '*' ? reg_magic >= MAGIC_ON : reg_magic == MAGIC_ALL), c);
    /* NOTREACHED */

  case Magic('~'): /* previous substitute pattern */
    if (reg_prev_sub != NULL)
    {
      char_u *lp;

      ret = regnode(EXACTLY);
      lp = reg_prev_sub;
      while (*lp != NUL)
        regc(*lp++);
      regc(NUL);
      if (*reg_prev_sub != NUL)
      {
        *flagp |= HASWIDTH;
        if ((lp - reg_prev_sub) == 1)
          *flagp |= SIMPLE;
      }
    }
    else
      EMSG_RET_NULL(_(e_nopresub));
    break;

  case Magic('1'):
  case Magic('2'):
  case Magic('3'):
  case Magic('4'):
  case Magic('5'):
  case Magic('6'):
  case Magic('7'):
  case Magic('8'):
  case Magic('9'):
  {
    int refnum;

    refnum = c - Magic('0');
    if (!seen_endbrace(refnum))
      return NULL;
    ret = regnode(BACKREF + refnum);
  }
  break;

  case Magic('z'):
  {
    c = no_Magic(getchr());
    switch (c)
    {

    case 's':
      ret = regnode(MOPEN + 0);
      if (re_mult_next("\\zs") == FAIL)
        return NULL;
      break;

    case 'e':
      ret = regnode(MCLOSE + 0);
      if (re_mult_next("\\ze") == FAIL)
        return NULL;
      break;

    default:
      EMSG_RET_NULL(_("E68: Invalid character after \\z"));
    }
  }
  break;

  case Magic('%'):
  {
    c = no_Magic(getchr());
    switch (c)
    {
    /* () without a back reference */
    case '(':
      if (one_exactly)
        EMSG_ONE_RET_NULL;
      ret = reg(REG_NPAREN, &flags);
      if (ret == NULL)
        return NULL;
      *flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
      break;

    /* Catch \%^ and \%$ regardless of where they appear in the
		 * pattern -- regardless of whether or not it makes sense. */
    case '^':
      ret = regnode(RE_BOF);
      break;

    case '$':
      ret = regnode(RE_EOF);
      break;

    case '#':
      ret = regnode(CURSOR);
      break;

    case 'V':
      ret = regnode(RE_VISUAL);
      break;

    case 'C':
      ret = regnode(RE_COMPOSING);
      break;

    /* \%[abc]: Emit as a list of branches, all ending at the last
		 * branch which matches nothing. */
    case '[':
      if (one_exactly) /* doesn't nest */
        EMSG_ONE_RET_NULL;
      {
        char_u *lastbranch;
        char_u *lastnode = NULL;
        char_u *br;

        ret = NULL;
        while ((c = getchr()) != ']')
        {
          if (c == NUL)
            EMSG2_RET_NULL(_(e_missing_sb),
                           reg_magic == MAGIC_ALL);
          br = regnode(BRANCH);
          if (ret == NULL)
            ret = br;
          else
            regtail(lastnode, br);

          ungetchr();
          one_exactly = TRUE;
          lastnode = regatom(flagp);
          one_exactly = FALSE;
          if (lastnode == NULL)
            return NULL;
        }
        if (ret == NULL)
          EMSG2_RET_NULL(_(e_empty_sb),
                         reg_magic == MAGIC_ALL);
        lastbranch = regnode(BRANCH);
        br = regnode(NOTHING);
        if (ret != JUST_CALC_SIZE)
        {
          regtail(lastnode, br);
          regtail(lastbranch, br);
          /* connect all branches to the NOTHING
				   * branch at the end */
          for (br = ret; br != lastnode;)
          {
            if (OP(br) == BRANCH)
            {
              regtail(br, lastbranch);
              br = OPERAND(br);
            }
            else
              br = regnext(br);
          }
        }
        *flagp &= ~(HASWIDTH | SIMPLE);
        break;
      }

    case 'd': /* %d123 decimal */
    case 'o': /* %o123 octal */
    case 'x': /* %xab hex 2 */
    case 'u': /* %uabcd hex 4 */
    case 'U': /* %U1234abcd hex 8 */
    {
      long i;

      switch (c)
      {
      case 'd':
        i = getdecchrs();
        break;
      case 'o':
        i = getoctchrs();
        break;
      case 'x':
        i = gethexchrs(2);
        break;
      case 'u':
        i = gethexchrs(4);
        break;
      case 'U':
        i = gethexchrs(8);
        break;
      default:
        i = -1;
        break;
      }

      if (i < 0 || i > INT_MAX)
        EMSG2_RET_NULL(
            _("E678: Invalid character after %s%%[dxouU]"),
            reg_magic == MAGIC_ALL);
      if (use_multibytecode(i))
        ret = regnode(MULTIBYTECODE);
      else
        ret = regnode(EXACTLY);
      if (i == 0)
        regc(0x0a);
      else
        regmbc(i);
      regc(NUL);
      *flagp |= HASWIDTH;
      break;
    }

    default:
      if (VIM_ISDIGIT(c) || c == '<' || c == '>' || c == '\'')
      {
        long_u n = 0;
        int cmp;

        cmp = c;
        if (cmp == '<' || cmp == '>')
          c = getchr();
        while (VIM_ISDIGIT(c))
        {
          n = n * 10 + (c - '0');
          c = getchr();
        }
        if (c == '\'' && n == 0)
        {
          /* "\%'m", "\%<'m" and "\%>'m": Mark */
          c = getchr();
          ret = regnode(RE_MARK);
          if (ret == JUST_CALC_SIZE)
            regsize += 2;
          else
          {
            *regcode++ = c;
            *regcode++ = cmp;
          }
          break;
        }
        else if (c == 'l' || c == 'c' || c == 'v')
        {
          if (c == 'l')
          {
            ret = regnode(RE_LNUM);
            if (save_prev_at_start)
              at_start = TRUE;
          }
          else if (c == 'c')
            ret = regnode(RE_COL);
          else
            ret = regnode(RE_VCOL);
          if (ret == JUST_CALC_SIZE)
            regsize += 5;
          else
          {
            /* put the number and the optional
				       * comparator after the opcode */
            regcode = re_put_long(regcode, n);
            *regcode++ = cmp;
          }
          break;
        }
      }

      EMSG2_RET_NULL(_("E71: Invalid character after %s%%"),
                     reg_magic == MAGIC_ALL);
    }
  }
  break;

  case Magic('['):
  collection:
  {
    char_u *lp;

    /*
	     * If there is no matching ']', we assume the '[' is a normal
	     * character.  This makes 'incsearch' and ":help [" work.
	     */
    lp = skip_anyof(regparse);
    if (*lp == ']') /* there is a matching ']' */
    {
      int startc = -1; /* > 0 when next '-' is a range */
      int endc;

      /*
		 * In a character class, different parsing rules apply.
		 * Not even \ is special anymore, nothing is.
		 */
      if (*regparse == '^') /* Complement of range. */
      {
        ret = regnode(ANYBUT + extra);
        regparse++;
      }
      else
        ret = regnode(ANYOF + extra);

      /* At the start ']' and '-' mean the literal character. */
      if (*regparse == ']' || *regparse == '-')
      {
        startc = *regparse;
        regc(*regparse++);
      }

      while (*regparse != NUL && *regparse != ']')
      {
        if (*regparse == '-')
        {
          ++regparse;
          /* The '-' is not used for a range at the end and
			 * after or before a '\n'. */
          if (*regparse == ']' || *regparse == NUL || startc == -1 || (regparse[0] == '\\' && regparse[1] == 'n'))
          {
            regc('-');
            startc = '-'; /* [--x] is a range */
          }
          else
          {
            /* Also accept "a-[.z.]" */
            endc = 0;
            if (*regparse == '[')
              endc = get_coll_element(&regparse);
            if (endc == 0)
            {
              if (has_mbyte)
                endc = mb_ptr2char_adv(&regparse);
              else
                endc = *regparse++;
            }

            /* Handle \o40, \x20 and \u20AC style sequences */
            if (endc == '\\' && !reg_cpo_lit && !reg_cpo_bsl)
              endc = coll_get_char();

            if (startc > endc)
              EMSG_RET_NULL(_(e_reverse_range));
            if (has_mbyte && ((*mb_char2len)(startc) > 1 || (*mb_char2len)(endc) > 1))
            {
              /* Limit to a range of 256 chars. */
              if (endc > startc + 256)
                EMSG_RET_NULL(_(e_large_class));
              while (++startc <= endc)
                regmbc(startc);
            }
            else
            {
#ifdef EBCDIC
              int alpha_only = FALSE;

              /* for alphabetical range skip the gaps
				 * 'i'-'j', 'r'-'s', 'I'-'J' and 'R'-'S'.  */
              if (isalpha(startc) && isalpha(endc))
                alpha_only = TRUE;
#endif
              while (++startc <= endc)
#ifdef EBCDIC
                if (!alpha_only || isalpha(startc))
#endif
                  regc(startc);
            }
            startc = -1;
          }
        }
        /*
		     * Only "\]", "\^", "\]" and "\\" are special in Vi.  Vim
		     * accepts "\t", "\e", etc., but only when the 'l' flag in
		     * 'cpoptions' is not included.
		     * Posix doesn't recognize backslash at all.
		     */
        else if (*regparse == '\\' && !reg_cpo_bsl && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL || (!reg_cpo_lit && vim_strchr(REGEXP_ABBR, regparse[1]) != NULL)))
        {
          regparse++;
          if (*regparse == 'n')
          {
            /* '\n' in range: also match NL */
            if (ret != JUST_CALC_SIZE)
            {
              /* Using \n inside [^] does not change what
				 * matches. "[^\n]" is the same as ".". */
              if (*ret == ANYOF)
              {
                *ret = ANYOF + ADD_NL;
                *flagp |= HASNL;
              }
              /* else: must have had a \n already */
            }
            regparse++;
            startc = -1;
          }
          else if (*regparse == 'd' || *regparse == 'o' || *regparse == 'x' || *regparse == 'u' || *regparse == 'U')
          {
            startc = coll_get_char();
            if (startc == 0)
              regc(0x0a);
            else
              regmbc(startc);
          }
          else
          {
            startc = backslash_trans(*regparse++);
            regc(startc);
          }
        }
        else if (*regparse == '[')
        {
          int c_class;
          int cu;

          c_class = get_char_class(&regparse);
          startc = -1;
          /* Characters assumed to be 8 bits! */
          switch (c_class)
          {
          case CLASS_NONE:
            c_class = get_equi_class(&regparse);
            if (c_class != 0)
            {
              /* produce equivalence class */
              reg_equi_class(c_class);
            }
            else if ((c_class =
                          get_coll_element(&regparse)) != 0)
            {
              /* produce a collating element */
              regmbc(c_class);
            }
            else
            {
              /* literal '[', allow [[-x] as a range */
              startc = *regparse++;
              regc(startc);
            }
            break;
          case CLASS_ALNUM:
            for (cu = 1; cu < 128; cu++)
              if (isalnum(cu))
                regmbc(cu);
            break;
          case CLASS_ALPHA:
            for (cu = 1; cu < 128; cu++)
              if (isalpha(cu))
                regmbc(cu);
            break;
          case CLASS_BLANK:
            regc(' ');
            regc('\t');
            break;
          case CLASS_CNTRL:
            for (cu = 1; cu <= 127; cu++)
              if (iscntrl(cu))
                regmbc(cu);
            break;
          case CLASS_DIGIT:
            for (cu = 1; cu <= 127; cu++)
              if (VIM_ISDIGIT(cu))
                regmbc(cu);
            break;
          case CLASS_GRAPH:
            for (cu = 1; cu <= 127; cu++)
              if (isgraph(cu))
                regmbc(cu);
            break;
          case CLASS_LOWER:
            for (cu = 1; cu <= 255; cu++)
              if (MB_ISLOWER(cu) && cu != 170 && cu != 186)
                regmbc(cu);
            break;
          case CLASS_PRINT:
            for (cu = 1; cu <= 255; cu++)
              if (vim_isprintc(cu))
                regmbc(cu);
            break;
          case CLASS_PUNCT:
            for (cu = 1; cu < 128; cu++)
              if (ispunct(cu))
                regmbc(cu);
            break;
          case CLASS_SPACE:
            for (cu = 9; cu <= 13; cu++)
              regc(cu);
            regc(' ');
            break;
          case CLASS_UPPER:
            for (cu = 1; cu <= 255; cu++)
              if (MB_ISUPPER(cu))
                regmbc(cu);
            break;
          case CLASS_XDIGIT:
            for (cu = 1; cu <= 255; cu++)
              if (vim_isxdigit(cu))
                regmbc(cu);
            break;
          case CLASS_TAB:
            regc('\t');
            break;
          case CLASS_RETURN:
            regc('\r');
            break;
          case CLASS_BACKSPACE:
            regc('\b');
            break;
          case CLASS_ESCAPE:
            regc('\033');
            break;
          case CLASS_IDENT:
            for (cu = 1; cu <= 255; cu++)
              if (vim_isIDc(cu))
                regmbc(cu);
            break;
          case CLASS_KEYWORD:
            for (cu = 1; cu <= 255; cu++)
              if (reg_iswordc(cu))
                regmbc(cu);
            break;
          case CLASS_FNAME:
            for (cu = 1; cu <= 255; cu++)
              if (vim_isfilec(cu))
                regmbc(cu);
            break;
          }
        }
        else
        {
          if (has_mbyte)
          {
            int len;

            /* produce a multibyte character, including any
			     * following composing characters */
            startc = mb_ptr2char(regparse);
            len = (*mb_ptr2len)(regparse);
            if (enc_utf8 && utf_char2len(startc) != len)
              startc = -1; /* composing chars */
            while (--len >= 0)
              regc(*regparse++);
          }
          else
          {
            startc = *regparse++;
            regc(startc);
          }
        }
      }
      regc(NUL);
      prevchr_len = 1; /* last char was the ']' */
      if (*regparse != ']')
        EMSG_RET_NULL(_(e_toomsbra)); /* Cannot happen? */
      skipchr();                      /* let's be friends with the lexer again */
      *flagp |= HASWIDTH | SIMPLE;
      break;
    }
    else if (reg_strict)
      EMSG2_RET_NULL(_(e_missingbracket), reg_magic > MAGIC_OFF);
  }
    /* FALLTHROUGH */

  default:
  {
    int len;

    /* A multi-byte character is handled as a separate atom if it's
	     * before a multi and when it's a composing char. */
    if (use_multibytecode(c))
    {
    do_multibyte:
      ret = regnode(MULTIBYTECODE);
      regmbc(c);
      *flagp |= HASWIDTH | SIMPLE;
      break;
    }

    ret = regnode(EXACTLY);

    /*
	     * Append characters as long as:
	     * - there is no following multi, we then need the character in
	     *   front of it as a single character operand
	     * - not running into a Magic character
	     * - "one_exactly" is not set
	     * But always emit at least one character.  Might be a Multi,
	     * e.g., a "[" without matching "]".
	     */
    for (len = 0; c != NUL && (len == 0 || (re_multi_type(peekchr()) == NOT_MULTI && !one_exactly && !is_Magic(c))); ++len)
    {
      c = no_Magic(c);
      if (has_mbyte)
      {
        regmbc(c);
        if (enc_utf8)
        {
          int l;

          /* Need to get composing character too. */
          for (;;)
          {
            l = utf_ptr2len(regparse);
            if (!UTF_COMPOSINGLIKE(regparse, regparse + l))
              break;
            regmbc(utf_ptr2char(regparse));
            skipchr();
          }
        }
      }
      else
        regc(c);
      c = getchr();
    }
    ungetchr();

    regc(NUL);
    *flagp |= HASWIDTH;
    if (len == 1)
      *flagp |= SIMPLE;
  }
  break;
  }

  return ret;
}

/*
 * Return TRUE if MULTIBYTECODE should be used instead of EXACTLY for
 * character "c".
 */
static int
use_multibytecode(int c)
{
  return has_mbyte && (*mb_char2len)(c) > 1 && (re_multi_type(peekchr()) != NOT_MULTI || (enc_utf8 && utf_iscomposing(c)));
}

/*
 * Emit a node.
 * Return pointer to generated code.
 */
static char_u *
regnode(int op)
{
  char_u *ret;

  ret = regcode;
  if (ret == JUST_CALC_SIZE)
    regsize += 3;
  else
  {
    *regcode++ = op;
    *regcode++ = NUL; /* Null "next" pointer. */
    *regcode++ = NUL;
  }
  return ret;
}

/*
 * Emit (if appropriate) a byte of code
 */
static void
regc(int b)
{
  if (regcode == JUST_CALC_SIZE)
    regsize++;
  else
    *regcode++ = b;
}

/*
 * Emit (if appropriate) a multi-byte character of code
 */
static void
regmbc(int c)
{
  if (!has_mbyte && c > 0xff)
    return;
  if (regcode == JUST_CALC_SIZE)
    regsize += (*mb_char2len)(c);
  else
    regcode += (*mb_char2bytes)(c, regcode);
}

/*
 * Insert an operator in front of already-emitted operand
 *
 * Means relocating the operand.
 */
static void
reginsert(int op, char_u *opnd)
{
  char_u *src;
  char_u *dst;
  char_u *place;

  if (regcode == JUST_CALC_SIZE)
  {
    regsize += 3;
    return;
  }
  src = regcode;
  regcode += 3;
  dst = regcode;
  while (src > opnd)
    *--dst = *--src;

  place = opnd; /* Op node, where operand used to be. */
  *place++ = op;
  *place++ = NUL;
  *place = NUL;
}

/*
 * Insert an operator in front of already-emitted operand.
 * Add a number to the operator.
 */
static void
reginsert_nr(int op, long val, char_u *opnd)
{
  char_u *src;
  char_u *dst;
  char_u *place;

  if (regcode == JUST_CALC_SIZE)
  {
    regsize += 7;
    return;
  }
  src = regcode;
  regcode += 7;
  dst = regcode;
  while (src > opnd)
    *--dst = *--src;

  place = opnd; /* Op node, where operand used to be. */
  *place++ = op;
  *place++ = NUL;
  *place++ = NUL;
  re_put_long(place, (long_u)val);
}

/*
 * Insert an operator in front of already-emitted operand.
 * The operator has the given limit values as operands.  Also set next pointer.
 *
 * Means relocating the operand.
 */
static void
reginsert_limits(
    int op,
    long minval,
    long maxval,
    char_u *opnd)
{
  char_u *src;
  char_u *dst;
  char_u *place;

  if (regcode == JUST_CALC_SIZE)
  {
    regsize += 11;
    return;
  }
  src = regcode;
  regcode += 11;
  dst = regcode;
  while (src > opnd)
    *--dst = *--src;

  place = opnd; /* Op node, where operand used to be. */
  *place++ = op;
  *place++ = NUL;
  *place++ = NUL;
  place = re_put_long(place, (long_u)minval);
  place = re_put_long(place, (long_u)maxval);
  regtail(opnd, place);
}

/*
 * Write a long as four bytes at "p" and return pointer to the next char.
 */
static char_u *
re_put_long(char_u *p, long_u val)
{
  *p++ = (char_u)((val >> 24) & 0377);
  *p++ = (char_u)((val >> 16) & 0377);
  *p++ = (char_u)((val >> 8) & 0377);
  *p++ = (char_u)(val & 0377);
  return p;
}

/*
 * Set the next-pointer at the end of a node chain.
 */
static void
regtail(char_u *p, char_u *val)
{
  char_u *scan;
  char_u *temp;
  int offset;

  if (p == JUST_CALC_SIZE)
    return;

  /* Find last node. */
  scan = p;
  for (;;)
  {
    temp = regnext(scan);
    if (temp == NULL)
      break;
    scan = temp;
  }

  if (OP(scan) == BACK)
    offset = (int)(scan - val);
  else
    offset = (int)(val - scan);
  /* When the offset uses more than 16 bits it can no longer fit in the two
     * bytes available.  Use a global flag to avoid having to check return
     * values in too many places. */
  if (offset > 0xffff)
    reg_toolong = TRUE;
  else
  {
    *(scan + 1) = (char_u)(((unsigned)offset >> 8) & 0377);
    *(scan + 2) = (char_u)(offset & 0377);
  }
}

/*
 * Like regtail, on item after a BRANCH; nop if none.
 */
static void
regoptail(char_u *p, char_u *val)
{
  /* When op is neither BRANCH nor BRACE_COMPLEX0-9, it is "operandless" */
  if (p == NULL || p == JUST_CALC_SIZE || (OP(p) != BRANCH && (OP(p) < BRACE_COMPLEX || OP(p) > BRACE_COMPLEX + 9)))
    return;
  regtail(OPERAND(p), val);
}

/*
 * Functions for getting characters from the regexp input.
 */
/*
 * Start parsing at "str".
 */
static void
initchr(char_u *str)
{
  regparse = str;
  prevchr_len = 0;
  curchr = prevprevchr = prevchr = nextchr = -1;
  at_start = TRUE;
  prev_at_start = FALSE;
}

/*
 * Save the current parse state, so that it can be restored and parsing
 * starts in the same state again.
 */
static void
save_parse_state(parse_state_T *ps)
{
  ps->regparse = regparse;
  ps->prevchr_len = prevchr_len;
  ps->curchr = curchr;
  ps->prevchr = prevchr;
  ps->prevprevchr = prevprevchr;
  ps->nextchr = nextchr;
  ps->at_start = at_start;
  ps->prev_at_start = prev_at_start;
  ps->regnpar = regnpar;
}

/*
 * Restore a previously saved parse state.
 */
static void
restore_parse_state(parse_state_T *ps)
{
  regparse = ps->regparse;
  prevchr_len = ps->prevchr_len;
  curchr = ps->curchr;
  prevchr = ps->prevchr;
  prevprevchr = ps->prevprevchr;
  nextchr = ps->nextchr;
  at_start = ps->at_start;
  prev_at_start = ps->prev_at_start;
  regnpar = ps->regnpar;
}

/*
 * Get the next character without advancing.
 */
static int
peekchr(void)
{
  static int after_slash = FALSE;

  if (curchr == -1)
  {
    switch (curchr = regparse[0])
    {
    case '.':
    case '[':
    case '~':
      /* magic when 'magic' is on */
      if (reg_magic >= MAGIC_ON)
        curchr = Magic(curchr);
      break;
    case '(':
    case ')':
    case '{':
    case '%':
    case '+':
    case '=':
    case '?':
    case '@':
    case '!':
    case '&':
    case '|':
    case '<':
    case '>':
    case '#':  /* future ext. */
    case '"':  /* future ext. */
    case '\'': /* future ext. */
    case ',':  /* future ext. */
    case '-':  /* future ext. */
    case ':':  /* future ext. */
    case ';':  /* future ext. */
    case '`':  /* future ext. */
    case '/':  /* Can't be used in / command */
      /* magic only after "\v" */
      if (reg_magic == MAGIC_ALL)
        curchr = Magic(curchr);
      break;
    case '*':
      /* * is not magic as the very first character, eg "?*ptr", when
	     * after '^', eg "/^*ptr" and when after "\(", "\|", "\&".  But
	     * "\(\*" is not magic, thus must be magic if "after_slash" */
      if (reg_magic >= MAGIC_ON && !at_start && !(prev_at_start && prevchr == Magic('^')) && (after_slash || (prevchr != Magic('(') && prevchr != Magic('&') && prevchr != Magic('|'))))
        curchr = Magic('*');
      break;
    case '^':
      /* '^' is only magic as the very first character and if it's after
	     * "\(", "\|", "\&' or "\n" */
      if (reg_magic >= MAGIC_OFF && (at_start || reg_magic == MAGIC_ALL || prevchr == Magic('(') || prevchr == Magic('|') || prevchr == Magic('&') || prevchr == Magic('n') || (no_Magic(prevchr) == '(' && prevprevchr == Magic('%'))))
      {
        curchr = Magic('^');
        at_start = TRUE;
        prev_at_start = FALSE;
      }
      break;
    case '$':
      /* '$' is only magic as the very last char and if it's in front of
	     * either "\|", "\)", "\&", or "\n" */
      if (reg_magic >= MAGIC_OFF)
      {
        char_u *p = regparse + 1;
        int is_magic_all = (reg_magic == MAGIC_ALL);

        /* ignore \c \C \m \M \v \V and \Z after '$' */
        while (p[0] == '\\' && (p[1] == 'c' || p[1] == 'C' || p[1] == 'm' || p[1] == 'M' || p[1] == 'v' || p[1] == 'V' || p[1] == 'Z'))
        {
          if (p[1] == 'v')
            is_magic_all = TRUE;
          else if (p[1] == 'm' || p[1] == 'M' || p[1] == 'V')
            is_magic_all = FALSE;
          p += 2;
        }
        if (p[0] == NUL || (p[0] == '\\' && (p[1] == '|' || p[1] == '&' || p[1] == ')' || p[1] == 'n')) || (is_magic_all && (p[0] == '|' || p[0] == '&' || p[0] == ')')) || reg_magic == MAGIC_ALL)
          curchr = Magic('$');
      }
      break;
    case '\\':
    {
      int c = regparse[1];

      if (c == NUL)
        curchr = '\\'; /* trailing '\' */
      else if (
#ifdef EBCDIC
          vim_strchr(META, c)
#else
          c <= '~' && META_flags[c]
#endif
      )
      {
        /*
		     * META contains everything that may be magic sometimes,
		     * except ^ and $ ("\^" and "\$" are only magic after
		     * "\V").  We now fetch the next character and toggle its
		     * magicness.  Therefore, \ is so meta-magic that it is
		     * not in META.
		     */
        curchr = -1;
        prev_at_start = at_start;
        at_start = FALSE; /* be able to say "/\*ptr" */
        ++regparse;
        ++after_slash;
        peekchr();
        --regparse;
        --after_slash;
        curchr = toggle_Magic(curchr);
      }
      else if (vim_strchr(REGEXP_ABBR, c))
      {
        /*
		     * Handle abbreviations, like "\t" for TAB -- webb
		     */
        curchr = backslash_trans(c);
      }
      else if (reg_magic == MAGIC_NONE && (c == '$' || c == '^'))
        curchr = toggle_Magic(c);
      else
      {
        /*
		     * Next character can never be (made) magic?
		     * Then backslashing it won't do anything.
		     */
        if (has_mbyte)
          curchr = (*mb_ptr2char)(regparse + 1);
        else
          curchr = c;
      }
      break;
    }

    default:
      if (has_mbyte)
        curchr = (*mb_ptr2char)(regparse);
    }
  }

  return curchr;
}

/*
 * Eat one lexed character.  Do this in a way that we can undo it.
 */
static void
skipchr(void)
{
  /* peekchr() eats a backslash, do the same here */
  if (*regparse == '\\')
    prevchr_len = 1;
  else
    prevchr_len = 0;
  if (regparse[prevchr_len] != NUL)
  {
    if (enc_utf8)
      /* exclude composing chars that mb_ptr2len does include */
      prevchr_len += utf_ptr2len(regparse + prevchr_len);
    else if (has_mbyte)
      prevchr_len += (*mb_ptr2len)(regparse + prevchr_len);
    else
      ++prevchr_len;
  }
  regparse += prevchr_len;
  prev_at_start = at_start;
  at_start = FALSE;
  prevprevchr = prevchr;
  prevchr = curchr;
  curchr = nextchr; /* use previously unget char, or -1 */
  nextchr = -1;
}

/*
 * Skip a character while keeping the value of prev_at_start for at_start.
 * prevchr and prevprevchr are also kept.
 */
static void
skipchr_keepstart(void)
{
  int as = prev_at_start;
  int pr = prevchr;
  int prpr = prevprevchr;

  skipchr();
  at_start = as;
  prevchr = pr;
  prevprevchr = prpr;
}

/*
 * Get the next character from the pattern. We know about magic and such, so
 * therefore we need a lexical analyzer.
 */
static int
getchr(void)
{
  int chr = peekchr();

  skipchr();
  return chr;
}

/*
 * put character back.  Works only once!
 */
static void
ungetchr(void)
{
  nextchr = curchr;
  curchr = prevchr;
  prevchr = prevprevchr;
  at_start = prev_at_start;
  prev_at_start = FALSE;

  /* Backup regparse, so that it's at the same position as before the
     * getchr(). */
  regparse -= prevchr_len;
}

/*
 * Get and return the value of the hex string at the current position.
 * Return -1 if there is no valid hex number.
 * The position is updated:
 *     blahblah\%x20asdf
 *	   before-^ ^-after
 * The parameter controls the maximum number of input characters. This will be
 * 2 when reading a \%x20 sequence and 4 when reading a \%u20AC sequence.
 */
static long
gethexchrs(int maxinputlen)
{
  long_u nr = 0;
  int c;
  int i;

  for (i = 0; i < maxinputlen; ++i)
  {
    c = regparse[0];
    if (!vim_isxdigit(c))
      break;
    nr <<= 4;
    nr |= hex2nr(c);
    ++regparse;
  }

  if (i == 0)
    return -1;
  return (long)nr;
}

/*
 * Get and return the value of the decimal string immediately after the
 * current position. Return -1 for invalid.  Consumes all digits.
 */
static long
getdecchrs(void)
{
  long_u nr = 0;
  int c;
  int i;

  for (i = 0;; ++i)
  {
    c = regparse[0];
    if (c < '0' || c > '9')
      break;
    nr *= 10;
    nr += c - '0';
    ++regparse;
    curchr = -1; /* no longer valid */
  }

  if (i == 0)
    return -1;
  return (long)nr;
}

/*
 * get and return the value of the octal string immediately after the current
 * position. Return -1 for invalid, or 0-255 for valid. Smart enough to handle
 * numbers > 377 correctly (for example, 400 is treated as 40) and doesn't
 * treat 8 or 9 as recognised characters. Position is updated:
 *     blahblah\%o210asdf
 *	   before-^  ^-after
 */
static long
getoctchrs(void)
{
  long_u nr = 0;
  int c;
  int i;

  for (i = 0; i < 3 && nr < 040; ++i)
  {
    c = regparse[0];
    if (c < '0' || c > '7')
      break;
    nr <<= 3;
    nr |= hex2nr(c);
    ++regparse;
  }

  if (i == 0)
    return -1;
  return (long)nr;
}

/*
 * Get a number after a backslash that is inside [].
 * When nothing is recognized return a backslash.
 */
static int
coll_get_char(void)
{
  long nr = -1;

  switch (*regparse++)
  {
  case 'd':
    nr = getdecchrs();
    break;
  case 'o':
    nr = getoctchrs();
    break;
  case 'x':
    nr = gethexchrs(2);
    break;
  case 'u':
    nr = gethexchrs(4);
    break;
  case 'U':
    nr = gethexchrs(8);
    break;
  }
  if (nr < 0 || nr > INT_MAX)
  {
    /* If getting the number fails be backwards compatible: the character
	 * is a backslash. */
    --regparse;
    nr = '\\';
  }
  return nr;
}

/*
 * read_limits - Read two integers to be taken as a minimum and maximum.
 * If the first character is '-', then the range is reversed.
 * Should end with 'end'.  If minval is missing, zero is default, if maxval is
 * missing, a very big number is the default.
 */
static int
read_limits(long *minval, long *maxval)
{
  int reverse = FALSE;
  char_u *first_char;
  long tmp;

  if (*regparse == '-')
  {
    /* Starts with '-', so reverse the range later */
    regparse++;
    reverse = TRUE;
  }
  first_char = regparse;
  *minval = getdigits(&regparse);
  if (*regparse == ',') /* There is a comma */
  {
    if (vim_isdigit(*++regparse))
      *maxval = getdigits(&regparse);
    else
      *maxval = MAX_LIMIT;
  }
  else if (VIM_ISDIGIT(*first_char))
    *maxval = *minval; /* It was \{n} or \{-n} */
  else
    *maxval = MAX_LIMIT; /* It was \{} or \{-} */
  if (*regparse == '\\')
    regparse++; /* Allow either \{...} or \{...\} */
  if (*regparse != '}')
    EMSG2_RET_FAIL(_("E554: Syntax error in %s{...}"),
                   reg_magic == MAGIC_ALL);

  /*
     * Reverse the range if there was a '-', or make sure it is in the right
     * order otherwise.
     */
  if ((!reverse && *minval > *maxval) || (reverse && *minval < *maxval))
  {
    tmp = *minval;
    *minval = *maxval;
    *maxval = tmp;
  }
  skipchr(); /* let's be friends with the lexer again */
  return OK;
}

/*
 * vim_regexec and friends
 */

/*
 * Global work variables for vim_regexec().
 */

/*
 * Structure used to save the current input state, when it needs to be
 * restored after trying a match.  Used by reg_save() and reg_restore().
 * Also stores the length of "backpos".
 */
typedef struct
{
  union
  {
    char_u *ptr; /* rex.input pointer, for single-line regexp */
    lpos_T pos;  /* rex.input pos, for multi-line regexp */
  } rs_u;
  int rs_len;
} regsave_T;

/* struct to save start/end pointer/position in for \(\) */
typedef struct
{
  union
  {
    char_u *ptr;
    lpos_T pos;
  } se_u;
} save_se_T;

/* used for BEHIND and NOBEHIND matching */
typedef struct regbehind_S
{
  regsave_T save_after;
  regsave_T save_behind;
  int save_need_clear_subexpr;
  save_se_T save_start[NSUBEXP];
  save_se_T save_end[NSUBEXP];
} regbehind_T;

static long bt_regexec_both(char_u *line, colnr_T col, proftime_T *tm, int *timed_out);
static long regtry(bt_regprog_T *prog, colnr_T col, proftime_T *tm, int *timed_out);
static void cleanup_subexpr(void);
static void save_subexpr(regbehind_T *bp);
static void restore_subexpr(regbehind_T *bp);
static void reg_nextline(void);
static void reg_save(regsave_T *save, garray_T *gap);
static void reg_restore(regsave_T *save, garray_T *gap);
static int reg_save_equal(regsave_T *save);
static void save_se_multi(save_se_T *savep, lpos_T *posp);
static void save_se_one(save_se_T *savep, char_u **pp);

/* Save the sub-expressions before attempting a match. */
#define save_se(savep, posp, pp) \
  REG_MULTI ? save_se_multi((savep), (posp)) : save_se_one((savep), (pp))

/* After a failed match restore the sub-expressions. */
#define restore_se(savep, posp, pp) \
  {                                 \
    if (REG_MULTI)                  \
      *(posp) = (savep)->se_u.pos;  \
    else                            \
      *(pp) = (savep)->se_u.ptr;    \
  }

static int re_num_cmp(long_u val, char_u *scan);
static int match_with_backref(linenr_T start_lnum, colnr_T start_col, linenr_T end_lnum, colnr_T end_col, int *bytelen);
static int regmatch(char_u *prog, proftime_T *tm, int *timed_out);
static int regrepeat(char_u *p, long maxcount);

#ifdef DEBUG
int regnarrate = 0;
#endif

/*
 * Sometimes need to save a copy of a line.  Since alloc()/free() is very
 * slow, we keep one allocated piece of memory and only re-allocate it when
 * it's too small.  It's freed in bt_regexec_both() when finished.
 */
static char_u *reg_tofree = NULL;
static unsigned reg_tofreelen;

/*
 * Structure used to store the execution state of the regex engine.
 * Which ones are set depends on whether a single-line or multi-line match is
 * done:
 *			single-line		multi-line
 * reg_match		&regmatch_T		NULL
 * reg_mmatch		NULL			&regmmatch_T
 * reg_startp		reg_match->startp	<invalid>
 * reg_endp		reg_match->endp		<invalid>
 * reg_startpos		<invalid>		reg_mmatch->startpos
 * reg_endpos		<invalid>		reg_mmatch->endpos
 * reg_win		NULL			window in which to search
 * reg_buf		curbuf			buffer in which to search
 * reg_firstlnum	<invalid>		first line in which to search
 * reg_maxline		0			last line nr
 * reg_line_lbr		FALSE or TRUE		FALSE
 */
typedef struct
{
  regmatch_T *reg_match;
  regmmatch_T *reg_mmatch;
  char_u **reg_startp;
  char_u **reg_endp;
  lpos_T *reg_startpos;
  lpos_T *reg_endpos;
  win_T *reg_win;
  buf_T *reg_buf;
  linenr_T reg_firstlnum;
  linenr_T reg_maxline;
  int reg_line_lbr; /* "\n" in string is line break */

  // The current match-position is stord in these variables:
  linenr_T lnum; // line number, relative to first line
  char_u *line;  // start of current line
  char_u *input; // current input, points into "regline"

  int need_clear_subexpr; // subexpressions still need to be cleared

  /* Internal copy of 'ignorecase'.  It is set at each call to vim_regexec().
     * Normally it gets the value of "rm_ic" or "rmm_ic", but when the pattern
     * contains '\c' or '\C' the value is overruled. */
  int reg_ic;

  /* Similar to "reg_ic", but only for 'combining' characters.  Set with \Z
     * flag in the regexp.  Defaults to false, always. */
  int reg_icombine;

  /* Copy of "rmm_maxcol": maximum column to search for a match.  Zero when
     * there is no maximum. */
  colnr_T reg_maxcol;

  // State for the NFA engine regexec.
  int nfa_has_zend;    // NFA regexp \ze operator encountered.
  int nfa_has_backref; // NFA regexp \1 .. \9 encountered.
  int nfa_nsubexpr;    // Number of sub expressions actually being used
                       // during execution. 1 if only the whole match
                       // (subexpr 0) is used.
  // listid is global, so that it increases on recursive calls to
  // nfa_regmatch(), which means we don't have to clear the lastlist field of
  // all the states.
  int nfa_listid;
  int nfa_alt_listid;

} regexec_T;

static regexec_T rex;
static int rex_in_use = FALSE;

/* Values for rs_state in regitem_T. */
typedef enum regstate_E
{
  RS_NOPEN = 0 /* NOPEN and NCLOSE */
  ,
  RS_MOPEN /* MOPEN + [0-9] */
  ,
  RS_MCLOSE /* MCLOSE + [0-9] */
  ,
  RS_BRANCH /* BRANCH */
  ,
  RS_BRCPLX_MORE /* BRACE_COMPLEX and trying one more match */
  ,
  RS_BRCPLX_LONG /* BRACE_COMPLEX and trying longest match */
  ,
  RS_BRCPLX_SHORT /* BRACE_COMPLEX and trying shortest match */
  ,
  RS_NOMATCH /* NOMATCH */
  ,
  RS_BEHIND1 /* BEHIND / NOBEHIND matching rest */
  ,
  RS_BEHIND2 /* BEHIND / NOBEHIND matching behind part */
  ,
  RS_STAR_LONG /* STAR/PLUS/BRACE_SIMPLE longest match */
  ,
  RS_STAR_SHORT /* STAR/PLUS/BRACE_SIMPLE shortest match */
} regstate_T;

/*
 * When there are alternatives a regstate_T is put on the regstack to remember
 * what we are doing.
 * Before it may be another type of item, depending on rs_state, to remember
 * more things.
 */
typedef struct regitem_S
{
  regstate_T rs_state; // what we are doing, one of RS_ above
  short rs_no;         // submatch nr or BEHIND/NOBEHIND
  char_u *rs_scan;     // current node in program
  union
  {
    save_se_T sesave;
    regsave_T regsave;
  } rs_un; // room for saving rex.input
} regitem_T;

static regitem_T *regstack_push(regstate_T state, char_u *scan);
static void regstack_pop(char_u **scan);

/* used for STAR, PLUS and BRACE_SIMPLE matching */
typedef struct regstar_S
{
  int nextb;    /* next byte */
  int nextb_ic; /* next byte reverse case */
  long count;
  long minval;
  long maxval;
} regstar_T;

/* used to store input position when a BACK was encountered, so that we now if
 * we made any progress since the last time. */
typedef struct backpos_S
{
  char_u *bp_scan;  /* "scan" where BACK was encountered */
  regsave_T bp_pos; /* last input position */
} backpos_T;

/*
 * "regstack" and "backpos" are used by regmatch().  They are kept over calls
 * to avoid invoking malloc() and free() often.
 * "regstack" is a stack with regitem_T items, sometimes preceded by regstar_T
 * or regbehind_T.
 * "backpos_T" is a table with backpos_T for BACK
 */
static garray_T regstack = {0, 0, 0, 0, NULL};
static garray_T backpos = {0, 0, 0, 0, NULL};

/*
 * Both for regstack and backpos tables we use the following strategy of
 * allocation (to reduce malloc/free calls):
 * - Initial size is fairly small.
 * - When needed, the tables are grown bigger (8 times at first, double after
 *   that).
 * - After executing the match we free the memory only if the array has grown.
 *   Thus the memory is kept allocated when it's at the initial size.
 * This makes it fast while not keeping a lot of memory allocated.
 * A three times speed increase was observed when using many simple patterns.
 */
#define REGSTACK_INITIAL 2048
#define BACKPOS_INITIAL 64

#if defined(EXITFREE) || defined(PROTO)
void free_regexp_stuff(void)
{
  ga_clear(&regstack);
  ga_clear(&backpos);
  vim_free(reg_tofree);
  vim_free(reg_prev_sub);
}
#endif

/*
 * Return TRUE if character 'c' is included in 'iskeyword' option for
 * "reg_buf" buffer.
 */
static int
reg_iswordc(int c)
{
  return vim_iswordc_buf(c, rex.reg_buf);
}

/*
 * Get pointer to the line "lnum", which is relative to "reg_firstlnum".
 */
static char_u *
reg_getline(linenr_T lnum)
{
  /* when looking behind for a match/no-match lnum is negative.  But we
     * can't go before line 1 */
  if (rex.reg_firstlnum + lnum < 1)
    return NULL;
  if (lnum > rex.reg_maxline)
    /* Must have matched the "\n" in the last line. */
    return (char_u *)"";
  return ml_get_buf(rex.reg_buf, rex.reg_firstlnum + lnum, FALSE);
}

static regsave_T behind_pos;

/* TRUE if using multi-line regexp. */
#define REG_MULTI (rex.reg_match == NULL)

/*
 * Match a regexp against a string.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 * if "line_lbr" is TRUE  consider a "\n" in "line" to be a line break.
 *
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
static int
bt_regexec_nl(
    regmatch_T *rmp,
    char_u *line, /* string to match against */
    colnr_T col,  /* column to start looking for match */
    int line_lbr)
{
  rex.reg_match = rmp;
  rex.reg_mmatch = NULL;
  rex.reg_maxline = 0;
  rex.reg_line_lbr = line_lbr;
  rex.reg_buf = curbuf;
  rex.reg_win = NULL;
  rex.reg_ic = rmp->rm_ic;
  rex.reg_icombine = FALSE;
  rex.reg_maxcol = 0;

  return bt_regexec_both(line, col, NULL, NULL);
}

/*
 * Match a regexp against multiple lines.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return zero if there is no match.  Return number of lines contained in the
 * match otherwise.
 */
static long
bt_regexec_multi(
    regmmatch_T *rmp,
    win_T *win,     /* window in which to search or NULL */
    buf_T *buf,     /* buffer in which to search */
    linenr_T lnum,  /* nr of line to start looking for match */
    colnr_T col,    /* column to start looking for match */
    proftime_T *tm, /* timeout limit or NULL */
    int *timed_out) /* flag set on timeout or NULL */
{
  rex.reg_match = NULL;
  rex.reg_mmatch = rmp;
  rex.reg_buf = buf;
  rex.reg_win = win;
  rex.reg_firstlnum = lnum;
  rex.reg_maxline = rex.reg_buf->b_ml.ml_line_count - lnum;
  rex.reg_line_lbr = FALSE;
  rex.reg_ic = rmp->rmm_ic;
  rex.reg_icombine = FALSE;
  rex.reg_maxcol = rmp->rmm_maxcol;

  return bt_regexec_both(NULL, col, tm, timed_out);
}

/*
 * Match a regexp against a string ("line" points to the string) or multiple
 * lines ("line" is NULL, use reg_getline()).
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
static long
bt_regexec_both(
    char_u *line,
    colnr_T col,    /* column to start looking for match */
    proftime_T *tm, /* timeout limit or NULL */
    int *timed_out) /* flag set on timeout or NULL */
{
  bt_regprog_T *prog;
  char_u *s;
  long retval = 0L;

  /* Create "regstack" and "backpos" if they are not allocated yet.
     * We allocate *_INITIAL amount of bytes first and then set the grow size
     * to much bigger value to avoid many malloc calls in case of deep regular
     * expressions.  */
  if (regstack.ga_data == NULL)
  {
    /* Use an item size of 1 byte, since we push different things
	 * onto the regstack. */
    ga_init2(&regstack, 1, REGSTACK_INITIAL);
    (void)ga_grow(&regstack, REGSTACK_INITIAL);
    regstack.ga_growsize = REGSTACK_INITIAL * 8;
  }

  if (backpos.ga_data == NULL)
  {
    ga_init2(&backpos, sizeof(backpos_T), BACKPOS_INITIAL);
    (void)ga_grow(&backpos, BACKPOS_INITIAL);
    backpos.ga_growsize = BACKPOS_INITIAL * 8;
  }

  if (REG_MULTI)
  {
    prog = (bt_regprog_T *)rex.reg_mmatch->regprog;
    line = reg_getline((linenr_T)0);
    rex.reg_startpos = rex.reg_mmatch->startpos;
    rex.reg_endpos = rex.reg_mmatch->endpos;
  }
  else
  {
    prog = (bt_regprog_T *)rex.reg_match->regprog;
    rex.reg_startp = rex.reg_match->startp;
    rex.reg_endp = rex.reg_match->endp;
  }

  /* Be paranoid... */
  if (prog == NULL || line == NULL)
  {
    emsg(_(e_null));
    goto theend;
  }

  /* Check validity of program. */
  if (prog_magic_wrong())
    goto theend;

  /* If the start column is past the maximum column: no need to try. */
  if (rex.reg_maxcol > 0 && col >= rex.reg_maxcol)
    goto theend;

  /* If pattern contains "\c" or "\C": overrule value of rex.reg_ic */
  if (prog->regflags & RF_ICASE)
    rex.reg_ic = TRUE;
  else if (prog->regflags & RF_NOICASE)
    rex.reg_ic = FALSE;

  /* If pattern contains "\Z" overrule value of rex.reg_icombine */
  if (prog->regflags & RF_ICOMBINE)
    rex.reg_icombine = TRUE;

  /* If there is a "must appear" string, look for it. */
  if (prog->regmust != NULL)
  {
    int c;

    if (has_mbyte)
      c = (*mb_ptr2char)(prog->regmust);
    else
      c = *prog->regmust;
    s = line + col;

    /*
	 * This is used very often, esp. for ":global".  Use three versions of
	 * the loop to avoid overhead of conditions.
	 */
    if (!rex.reg_ic && !has_mbyte)
      while ((s = vim_strbyte(s, c)) != NULL)
      {
        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
          break; /* Found it. */
        ++s;
      }
    else if (!rex.reg_ic || (!enc_utf8 && mb_char2len(c) > 1))
      while ((s = vim_strchr(s, c)) != NULL)
      {
        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
          break; /* Found it. */
        MB_PTR_ADV(s);
      }
    else
      while ((s = cstrchr(s, c)) != NULL)
      {
        if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
          break; /* Found it. */
        MB_PTR_ADV(s);
      }
    if (s == NULL) /* Not present. */
      goto theend;
  }

  rex.line = line;
  rex.lnum = 0;
  reg_toolong = FALSE;

  /* Simplest case: Anchored match need be tried only once. */
  if (prog->reganch)
  {
    int c;

    if (has_mbyte)
      c = (*mb_ptr2char)(rex.line + col);
    else
      c = rex.line[col];
    if (prog->regstart == NUL || prog->regstart == c || (rex.reg_ic && (((enc_utf8 && utf_fold(prog->regstart) == utf_fold(c))) || (c < 255 && prog->regstart < 255 && MB_TOLOWER(prog->regstart) == MB_TOLOWER(c)))))
      retval = regtry(prog, col, tm, timed_out);
    else
      retval = 0;
  }
  else
  {
#ifdef FEAT_RELTIME
    int tm_count = 0;
#endif
    /* Messy cases:  unanchored match. */
    while (!got_int)
    {
      if (prog->regstart != NUL)
      {
        /* Skip until the char we know it must start with.
		 * Used often, do some work to avoid call overhead. */
        if (!rex.reg_ic && !has_mbyte)
          s = vim_strbyte(rex.line + col, prog->regstart);
        else
          s = cstrchr(rex.line + col, prog->regstart);
        if (s == NULL)
        {
          retval = 0;
          break;
        }
        col = (int)(s - rex.line);
      }

      /* Check for maximum column to try. */
      if (rex.reg_maxcol > 0 && col >= rex.reg_maxcol)
      {
        retval = 0;
        break;
      }

      retval = regtry(prog, col, tm, timed_out);
      if (retval > 0)
        break;

      /* if not currently on the first line, get it again */
      if (rex.lnum != 0)
      {
        rex.lnum = 0;
        rex.line = reg_getline((linenr_T)0);
      }
      if (rex.line[col] == NUL)
        break;
      if (has_mbyte)
        col += (*mb_ptr2len)(rex.line + col);
      else
        ++col;
#ifdef FEAT_RELTIME
      /* Check for timeout once in a twenty times to avoid overhead. */
      if (tm != NULL && ++tm_count == 20)
      {
        tm_count = 0;
        if (profile_passed_limit(tm))
        {
          if (timed_out != NULL)
            *timed_out = TRUE;
          break;
        }
      }
#endif
    }
  }

theend:
  /* Free "reg_tofree" when it's a bit big.
     * Free regstack and backpos if they are bigger than their initial size. */
  if (reg_tofreelen > 400)
    VIM_CLEAR(reg_tofree);
  if (regstack.ga_maxlen > REGSTACK_INITIAL)
    ga_clear(&regstack);
  if (backpos.ga_maxlen > BACKPOS_INITIAL)
    ga_clear(&backpos);

  return retval;
}

/*
 * regtry - try match of "prog" with at rex.line["col"].
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
static long
regtry(
    bt_regprog_T *prog,
    colnr_T col,
    proftime_T *tm, /* timeout limit or NULL */
    int *timed_out) /* flag set on timeout or NULL */
{
  rex.input = rex.line + col;
  rex.need_clear_subexpr = TRUE;

  if (regmatch(prog->program + 1, tm, timed_out) == 0)
    return 0;

  cleanup_subexpr();
  if (REG_MULTI)
  {
    if (rex.reg_startpos[0].lnum < 0)
    {
      rex.reg_startpos[0].lnum = 0;
      rex.reg_startpos[0].col = col;
    }
    if (rex.reg_endpos[0].lnum < 0)
    {
      rex.reg_endpos[0].lnum = rex.lnum;
      rex.reg_endpos[0].col = (int)(rex.input - rex.line);
    }
    else
      /* Use line number of "\ze". */
      rex.lnum = rex.reg_endpos[0].lnum;
  }
  else
  {
    if (rex.reg_startp[0] == NULL)
      rex.reg_startp[0] = rex.line + col;
    if (rex.reg_endp[0] == NULL)
      rex.reg_endp[0] = rex.input;
  }
  return 1 + rex.lnum;
}

/*
 * Get class of previous character.
 */
static int
reg_prev_class(void)
{
  if (rex.input > rex.line)
    return mb_get_class_buf(rex.input - 1 - (*mb_head_off)(rex.line, rex.input - 1), rex.reg_buf);
  return -1;
}

/*
 * Return TRUE if the current rex.input position matches the Visual area.
 */
static int
reg_match_visual(void)
{
  pos_T top, bot;
  linenr_T lnum;
  colnr_T col;
  win_T *wp = rex.reg_win == NULL ? curwin : rex.reg_win;
  int mode;
  colnr_T start, end;
  colnr_T start2, end2;
  colnr_T cols;

  /* Check if the buffer is the current buffer. */
  if (rex.reg_buf != curbuf || VIsual.lnum == 0)
    return FALSE;

  if (VIsual_active)
  {
    if (LT_POS(VIsual, wp->w_cursor))
    {
      top = VIsual;
      bot = wp->w_cursor;
    }
    else
    {
      top = wp->w_cursor;
      bot = VIsual;
    }
    mode = VIsual_mode;
  }
  else
  {
    if (LT_POS(curbuf->b_visual.vi_start, curbuf->b_visual.vi_end))
    {
      top = curbuf->b_visual.vi_start;
      bot = curbuf->b_visual.vi_end;
    }
    else
    {
      top = curbuf->b_visual.vi_end;
      bot = curbuf->b_visual.vi_start;
    }
    mode = curbuf->b_visual.vi_mode;
  }
  lnum = rex.lnum + rex.reg_firstlnum;
  if (lnum < top.lnum || lnum > bot.lnum)
    return FALSE;

  if (mode == 'v')
  {
    col = (colnr_T)(rex.input - rex.line);
    if ((lnum == top.lnum && col < top.col) || (lnum == bot.lnum && col >= bot.col + (*p_sel != 'e')))
      return FALSE;
  }
  else if (mode == Ctrl_V)
  {
    getvvcol(wp, &top, &start, NULL, &end);
    getvvcol(wp, &bot, &start2, NULL, &end2);
    if (start2 < start)
      start = start2;
    if (end2 > end)
      end = end2;
    if (top.col == MAXCOL || bot.col == MAXCOL)
      end = MAXCOL;
    cols = win_linetabsize(wp, rex.line, (colnr_T)(rex.input - rex.line));
    if (cols < start || cols > end - (*p_sel == 'e'))
      return FALSE;
  }
  return TRUE;
}

#define ADVANCE_REGINPUT() MB_PTR_ADV(rex.input)

/*
 * The arguments from BRACE_LIMITS are stored here.  They are actually local
 * to regmatch(), but they are here to reduce the amount of stack space used
 * (it can be called recursively many times).
 */
static long bl_minval;
static long bl_maxval;

/*
 * regmatch - main matching routine
 *
 * Conceptually the strategy is simple: Check to see whether the current node
 * matches, push an item onto the regstack and loop to see whether the rest
 * matches, and then act accordingly.  In practice we make some effort to
 * avoid using the regstack, in particular by going through "ordinary" nodes
 * (that don't need to know whether the rest of the match failed) by a nested
 * loop.
 *
 * Returns TRUE when there is a match.  Leaves rex.input and rex.lnum just after
 * the last matched character.
 * Returns FALSE when there is no match.  Leaves rex.input and rex.lnum in an
 * undefined state!
 */
static int
regmatch(
    char_u *scan,          /* Current node. */
    proftime_T *tm UNUSED, /* timeout limit or NULL */
    int *timed_out UNUSED) /* flag set on timeout or NULL */
{
  char_u *next; /* Next node. */
  int op;
  int c;
  regitem_T *rp;
  int no;
  int status;        /* one of the RA_ values: */
#define RA_FAIL 1    /* something failed, abort */
#define RA_CONT 2    /* continue in inner loop */
#define RA_BREAK 3   /* break inner loop */
#define RA_MATCH 4   /* successful match */
#define RA_NOMATCH 5 /* didn't match */
#ifdef FEAT_RELTIME
  int tm_count = 0;
#endif

  /* Make "regstack" and "backpos" empty.  They are allocated and freed in
   * bt_regexec_both() to reduce malloc()/free() calls. */
  regstack.ga_len = 0;
  backpos.ga_len = 0;

  /*
   * Repeat until "regstack" is empty.
   */
  for (;;)
  {
    /* Some patterns may take a long time to match, e.g., "\([a-z]\+\)\+Q".
     * Allow interrupting them with CTRL-C. */
    fast_breakcheck();

#ifdef DEBUG
    if (scan != NULL && regnarrate)
    {
      mch_errmsg((char *)regprop(scan));
      mch_errmsg("(\n");
    }
#endif

    /*
     * Repeat for items that can be matched sequentially, without using the
     * regstack.
     */
    for (;;)
    {
      if (got_int || scan == NULL)
      {
        status = RA_FAIL;
        break;
      }
#ifdef FEAT_RELTIME
      /* Check for timeout once in a 100 times to avoid overhead. */
      if (tm != NULL && ++tm_count == 100)
      {
        tm_count = 0;
        if (profile_passed_limit(tm))
        {
          if (timed_out != NULL)
            *timed_out = TRUE;
          status = RA_FAIL;
          break;
        }
      }
#endif
      status = RA_CONT;

#ifdef DEBUG
      if (regnarrate)
      {
        mch_errmsg((char *)regprop(scan));
        mch_errmsg("...\n");
      }
#endif
      next = regnext(scan);

      op = OP(scan);
      /* Check for character class with NL added. */
      if (!rex.reg_line_lbr && WITH_NL(op) && REG_MULTI && *rex.input == NUL && rex.lnum <= rex.reg_maxline)
      {
        reg_nextline();
      }
      else if (rex.reg_line_lbr && WITH_NL(op) && *rex.input == '\n')
      {
        ADVANCE_REGINPUT();
      }
      else
      {
        if (WITH_NL(op))
          op -= ADD_NL;
        if (has_mbyte)
          c = (*mb_ptr2char)(rex.input);
        else
          c = *rex.input;
        switch (op)
        {
        case BOL:
          if (rex.input != rex.line)
            status = RA_NOMATCH;
          break;

        case EOL:
          if (c != NUL)
            status = RA_NOMATCH;
          break;

        case RE_BOF:
          /* We're not at the beginning of the file when below the first
	     * line where we started, not at the start of the line or we
	     * didn't start at the first line of the buffer. */
          if (rex.lnum != 0 || rex.input != rex.line || (REG_MULTI && rex.reg_firstlnum > 1))
            status = RA_NOMATCH;
          break;

        case RE_EOF:
          if (rex.lnum != rex.reg_maxline || c != NUL)
            status = RA_NOMATCH;
          break;

        case CURSOR:
          /* Check if the buffer is in a window and compare the
	     * rex.reg_win->w_cursor position to the match position. */
          if (rex.reg_win == NULL || (rex.lnum + rex.reg_firstlnum != rex.reg_win->w_cursor.lnum) || ((colnr_T)(rex.input - rex.line) != rex.reg_win->w_cursor.col))
            status = RA_NOMATCH;
          break;

        case RE_MARK:
          /* Compare the mark position to the match position. */
          {
            int mark = OPERAND(scan)[0];
            int cmp = OPERAND(scan)[1];
            pos_T *pos;

            pos = getmark_buf(rex.reg_buf, mark, FALSE);
            if (pos == NULL       /* mark doesn't exist */
                || pos->lnum <= 0 /* mark isn't set in reg_buf */
                || (pos->lnum == rex.lnum + rex.reg_firstlnum
                        ? (pos->col == (colnr_T)(rex.input - rex.line)
                               ? (cmp == '<' || cmp == '>')
                               : (pos->col < (colnr_T)(rex.input - rex.line)
                                      ? cmp != '>'
                                      : cmp != '<'))
                        : (pos->lnum < rex.lnum + rex.reg_firstlnum
                               ? cmp != '>'
                               : cmp != '<')))
              status = RA_NOMATCH;
          }
          break;

        case RE_VISUAL:
          if (!reg_match_visual())
            status = RA_NOMATCH;
          break;

        case RE_LNUM:
          if (!REG_MULTI || !re_num_cmp((long_u)(rex.lnum + rex.reg_firstlnum),
                                        scan))
            status = RA_NOMATCH;
          break;

        case RE_COL:
          if (!re_num_cmp((long_u)(rex.input - rex.line) + 1, scan))
            status = RA_NOMATCH;
          break;

        case RE_VCOL:
          if (!re_num_cmp((long_u)win_linetabsize(
                              rex.reg_win == NULL ? curwin : rex.reg_win,
                              rex.line, (colnr_T)(rex.input - rex.line)) +
                              1,
                          scan))
            status = RA_NOMATCH;
          break;

        case BOW:       /* \<word; rex.input points to w */
          if (c == NUL) /* Can't match at end of line */
            status = RA_NOMATCH;
          else if (has_mbyte)
          {
            int this_class;

            /* Get class of current and previous char (if it exists). */
            this_class = mb_get_class_buf(rex.input, rex.reg_buf);
            if (this_class <= 1)
              status = RA_NOMATCH; /* not on a word at all */
            else if (reg_prev_class() == this_class)
              status = RA_NOMATCH; /* previous char is in same word */
          }
          else
          {
            if (!vim_iswordc_buf(c, rex.reg_buf) || (rex.input > rex.line && vim_iswordc_buf(rex.input[-1], rex.reg_buf)))
              status = RA_NOMATCH;
          }
          break;

        case EOW:                    /* word\>; rex.input points after d */
          if (rex.input == rex.line) /* Can't match at start of line */
            status = RA_NOMATCH;
          else if (has_mbyte)
          {
            int this_class, prev_class;

            /* Get class of current and previous char (if it exists). */
            this_class = mb_get_class_buf(rex.input, rex.reg_buf);
            prev_class = reg_prev_class();
            if (this_class == prev_class || prev_class == 0 || prev_class == 1)
              status = RA_NOMATCH;
          }
          else
          {
            if (!vim_iswordc_buf(rex.input[-1], rex.reg_buf) || (rex.input[0] != NUL && vim_iswordc_buf(c, rex.reg_buf)))
              status = RA_NOMATCH;
          }
          break; /* Matched with EOW */

        case ANY:
          /* ANY does not match new lines. */
          if (c == NUL)
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case IDENT:
          if (!vim_isIDc(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case SIDENT:
          if (VIM_ISDIGIT(*rex.input) || !vim_isIDc(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case KWORD:
          if (!vim_iswordp_buf(rex.input, rex.reg_buf))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case SKWORD:
          if (VIM_ISDIGIT(*rex.input) || !vim_iswordp_buf(rex.input, rex.reg_buf))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case FNAME:
          if (!vim_isfilec(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case SFNAME:
          if (VIM_ISDIGIT(*rex.input) || !vim_isfilec(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case PRINT:
          if (!vim_isprintc(PTR2CHAR(rex.input)))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case SPRINT:
          if (VIM_ISDIGIT(*rex.input) || !vim_isprintc(PTR2CHAR(rex.input)))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case WHITE:
          if (!VIM_ISWHITE(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NWHITE:
          if (c == NUL || VIM_ISWHITE(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case DIGIT:
          if (!ri_digit(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NDIGIT:
          if (c == NUL || ri_digit(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case HEX:
          if (!ri_hex(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NHEX:
          if (c == NUL || ri_hex(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case OCTAL:
          if (!ri_octal(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NOCTAL:
          if (c == NUL || ri_octal(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case WORD:
          if (!ri_word(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NWORD:
          if (c == NUL || ri_word(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case HEAD:
          if (!ri_head(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NHEAD:
          if (c == NUL || ri_head(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case ALPHA:
          if (!ri_alpha(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NALPHA:
          if (c == NUL || ri_alpha(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case LOWER:
          if (!ri_lower(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NLOWER:
          if (c == NUL || ri_lower(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case UPPER:
          if (!ri_upper(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case NUPPER:
          if (c == NUL || ri_upper(c))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case EXACTLY:
        {
          int len;
          char_u *opnd;

          opnd = OPERAND(scan);
          /* Inline the first byte, for speed. */
          if (*opnd != *rex.input && (!rex.reg_ic || (!enc_utf8 && MB_TOLOWER(*opnd) != MB_TOLOWER(*rex.input))))
            status = RA_NOMATCH;
          else if (*opnd == NUL)
          {
            /* match empty string always works; happens when "~" is
		     * empty. */
          }
          else
          {
            if (opnd[1] == NUL && !(enc_utf8 && rex.reg_ic))
            {
              len = 1; /* matched a single byte above */
            }
            else
            {
              /* Need to match first byte again for multi-byte. */
              len = (int)STRLEN(opnd);
              if (cstrncmp(opnd, rex.input, &len) != 0)
                status = RA_NOMATCH;
            }
            /* Check for following composing character, unless %C
		     * follows (skips over all composing chars). */
            if (status != RA_NOMATCH && enc_utf8 && UTF_COMPOSINGLIKE(rex.input, rex.input + len) && !rex.reg_icombine && OP(next) != RE_COMPOSING)
            {
              /* raaron: This code makes a composing character get
			 * ignored, which is the correct behavior (sometimes)
			 * for voweled Hebrew texts. */
              status = RA_NOMATCH;
            }
            if (status != RA_NOMATCH)
              rex.input += len;
          }
        }
        break;

        case ANYOF:
        case ANYBUT:
          if (c == NUL)
            status = RA_NOMATCH;
          else if ((cstrchr(OPERAND(scan), c) == NULL) == (op == ANYOF))
            status = RA_NOMATCH;
          else
            ADVANCE_REGINPUT();
          break;

        case MULTIBYTECODE:
          if (has_mbyte)
          {
            int i, len;
            char_u *opnd;
            int opndc = 0, inpc;

            opnd = OPERAND(scan);
            /* Safety check (just in case 'encoding' was changed since
		 * compiling the program). */
            if ((len = (*mb_ptr2len)(opnd)) < 2)
            {
              status = RA_NOMATCH;
              break;
            }
            if (enc_utf8)
              opndc = utf_ptr2char(opnd);
            if (enc_utf8 && utf_iscomposing(opndc))
            {
              /* When only a composing char is given match at any
		     * position where that composing char appears. */
              status = RA_NOMATCH;
              for (i = 0; rex.input[i] != NUL;
                   i += utf_ptr2len(rex.input + i))
              {
                inpc = utf_ptr2char(rex.input + i);
                if (!utf_iscomposing(inpc))
                {
                  if (i > 0)
                    break;
                }
                else if (opndc == inpc)
                {
                  /* Include all following composing chars. */
                  len = i + utfc_ptr2len(rex.input + i);
                  status = RA_MATCH;
                  break;
                }
              }
            }
            else
              for (i = 0; i < len; ++i)
                if (opnd[i] != rex.input[i])
                {
                  status = RA_NOMATCH;
                  break;
                }
            rex.input += len;
          }
          else
            status = RA_NOMATCH;
          break;
        case RE_COMPOSING:
          if (enc_utf8)
          {
            /* Skip composing characters. */
            while (utf_iscomposing(utf_ptr2char(rex.input)))
              MB_CPTR_ADV(rex.input);
          }
          break;

        case NOTHING:
          break;

        case BACK:
        {
          int i;
          backpos_T *bp;

          /*
		 * When we run into BACK we need to check if we don't keep
		 * looping without matching any input.  The second and later
		 * times a BACK is encountered it fails if the input is still
		 * at the same position as the previous time.
		 * The positions are stored in "backpos" and found by the
		 * current value of "scan", the position in the RE program.
		 */
          bp = (backpos_T *)backpos.ga_data;
          for (i = 0; i < backpos.ga_len; ++i)
            if (bp[i].bp_scan == scan)
              break;
          if (i == backpos.ga_len)
          {
            /* First time at this BACK, make room to store the pos. */
            if (ga_grow(&backpos, 1) == FAIL)
              status = RA_FAIL;
            else
            {
              /* get "ga_data" again, it may have changed */
              bp = (backpos_T *)backpos.ga_data;
              bp[i].bp_scan = scan;
              ++backpos.ga_len;
            }
          }
          else if (reg_save_equal(&bp[i].bp_pos))
            /* Still at same position as last time, fail. */
            status = RA_NOMATCH;

          if (status != RA_FAIL && status != RA_NOMATCH)
            reg_save(&bp[i].bp_pos, &backpos);
        }
        break;

        case MOPEN + 0: /* Match start: \zs */
        case MOPEN + 1: /* \( */
        case MOPEN + 2:
        case MOPEN + 3:
        case MOPEN + 4:
        case MOPEN + 5:
        case MOPEN + 6:
        case MOPEN + 7:
        case MOPEN + 8:
        case MOPEN + 9:
        {
          no = op - MOPEN;
          cleanup_subexpr();
          rp = regstack_push(RS_MOPEN, scan);
          if (rp == NULL)
            status = RA_FAIL;
          else
          {
            rp->rs_no = no;
            save_se(&rp->rs_un.sesave, &rex.reg_startpos[no],
                    &rex.reg_startp[no]);
            /* We simply continue and handle the result when done. */
          }
        }
        break;

        case NOPEN:  /* \%( */
        case NCLOSE: /* \) after \%( */
          if (regstack_push(RS_NOPEN, scan) == NULL)
            status = RA_FAIL;
          /* We simply continue and handle the result when done. */
          break;

        case MCLOSE + 0: /* Match end: \ze */
        case MCLOSE + 1: /* \) */
        case MCLOSE + 2:
        case MCLOSE + 3:
        case MCLOSE + 4:
        case MCLOSE + 5:
        case MCLOSE + 6:
        case MCLOSE + 7:
        case MCLOSE + 8:
        case MCLOSE + 9:
        {
          no = op - MCLOSE;
          cleanup_subexpr();
          rp = regstack_push(RS_MCLOSE, scan);
          if (rp == NULL)
            status = RA_FAIL;
          else
          {
            rp->rs_no = no;
            save_se(&rp->rs_un.sesave, &rex.reg_endpos[no],
                    &rex.reg_endp[no]);
            /* We simply continue and handle the result when done. */
          }
        }
        break;

        case BACKREF + 1:
        case BACKREF + 2:
        case BACKREF + 3:
        case BACKREF + 4:
        case BACKREF + 5:
        case BACKREF + 6:
        case BACKREF + 7:
        case BACKREF + 8:
        case BACKREF + 9:
        {
          int len;

          no = op - BACKREF;
          cleanup_subexpr();
          if (!REG_MULTI) /* Single-line regexp */
          {
            if (rex.reg_startp[no] == NULL || rex.reg_endp[no] == NULL)
            {
              /* Backref was not set: Match an empty string. */
              len = 0;
            }
            else
            {
              /* Compare current input with back-ref in the same
			 * line. */
              len = (int)(rex.reg_endp[no] - rex.reg_startp[no]);
              if (cstrncmp(rex.reg_startp[no], rex.input, &len) != 0)
                status = RA_NOMATCH;
            }
          }
          else /* Multi-line regexp */
          {
            if (rex.reg_startpos[no].lnum < 0 || rex.reg_endpos[no].lnum < 0)
            {
              /* Backref was not set: Match an empty string. */
              len = 0;
            }
            else
            {
              if (rex.reg_startpos[no].lnum == rex.lnum && rex.reg_endpos[no].lnum == rex.lnum)
              {
                /* Compare back-ref within the current line. */
                len = rex.reg_endpos[no].col - rex.reg_startpos[no].col;
                if (cstrncmp(rex.line + rex.reg_startpos[no].col,
                             rex.input, &len) != 0)
                  status = RA_NOMATCH;
              }
              else
              {
                /* Messy situation: Need to compare between two
			     * lines. */
                int r = match_with_backref(
                    rex.reg_startpos[no].lnum,
                    rex.reg_startpos[no].col,
                    rex.reg_endpos[no].lnum,
                    rex.reg_endpos[no].col,
                    &len);

                if (r != RA_MATCH)
                  status = r;
              }
            }
          }

          /* Matched the backref, skip over it. */
          rex.input += len;
        }
        break;

        case BRANCH:
        {
          if (OP(next) != BRANCH) /* No choice. */
            next = OPERAND(scan); /* Avoid recursion. */
          else
          {
            rp = regstack_push(RS_BRANCH, scan);
            if (rp == NULL)
              status = RA_FAIL;
            else
              status = RA_BREAK; /* rest is below */
          }
        }
        break;

        case BRACE_LIMITS:
        {
          if (OP(next) == BRACE_SIMPLE)
          {
            bl_minval = OPERAND_MIN(scan);
            bl_maxval = OPERAND_MAX(scan);
          }
          else if (OP(next) >= BRACE_COMPLEX && OP(next) < BRACE_COMPLEX + 10)
          {
            no = OP(next) - BRACE_COMPLEX;
            brace_min[no] = OPERAND_MIN(scan);
            brace_max[no] = OPERAND_MAX(scan);
            brace_count[no] = 0;
          }
          else
          {
            internal_error("BRACE_LIMITS");
            status = RA_FAIL;
          }
        }
        break;

        case BRACE_COMPLEX + 0:
        case BRACE_COMPLEX + 1:
        case BRACE_COMPLEX + 2:
        case BRACE_COMPLEX + 3:
        case BRACE_COMPLEX + 4:
        case BRACE_COMPLEX + 5:
        case BRACE_COMPLEX + 6:
        case BRACE_COMPLEX + 7:
        case BRACE_COMPLEX + 8:
        case BRACE_COMPLEX + 9:
        {
          no = op - BRACE_COMPLEX;
          ++brace_count[no];

          /* If not matched enough times yet, try one more */
          if (brace_count[no] <= (brace_min[no] <= brace_max[no]
                                      ? brace_min[no]
                                      : brace_max[no]))
          {
            rp = regstack_push(RS_BRCPLX_MORE, scan);
            if (rp == NULL)
              status = RA_FAIL;
            else
            {
              rp->rs_no = no;
              reg_save(&rp->rs_un.regsave, &backpos);
              next = OPERAND(scan);
              /* We continue and handle the result when done. */
            }
            break;
          }

          /* If matched enough times, may try matching some more */
          if (brace_min[no] <= brace_max[no])
          {
            /* Range is the normal way around, use longest match */
            if (brace_count[no] <= brace_max[no])
            {
              rp = regstack_push(RS_BRCPLX_LONG, scan);
              if (rp == NULL)
                status = RA_FAIL;
              else
              {
                rp->rs_no = no;
                reg_save(&rp->rs_un.regsave, &backpos);
                next = OPERAND(scan);
                /* We continue and handle the result when done. */
              }
            }
          }
          else
          {
            /* Range is backwards, use shortest match first */
            if (brace_count[no] <= brace_min[no])
            {
              rp = regstack_push(RS_BRCPLX_SHORT, scan);
              if (rp == NULL)
                status = RA_FAIL;
              else
              {
                reg_save(&rp->rs_un.regsave, &backpos);
                /* We continue and handle the result when done. */
              }
            }
          }
        }
        break;

        case BRACE_SIMPLE:
        case STAR:
        case PLUS:
        {
          regstar_T rst;

          /*
		 * Lookahead to avoid useless match attempts when we know
		 * what character comes next.
		 */
          if (OP(next) == EXACTLY)
          {
            rst.nextb = *OPERAND(next);
            if (rex.reg_ic)
            {
              if (MB_ISUPPER(rst.nextb))
                rst.nextb_ic = MB_TOLOWER(rst.nextb);
              else
                rst.nextb_ic = MB_TOUPPER(rst.nextb);
            }
            else
              rst.nextb_ic = rst.nextb;
          }
          else
          {
            rst.nextb = NUL;
            rst.nextb_ic = NUL;
          }
          if (op != BRACE_SIMPLE)
          {
            rst.minval = (op == STAR) ? 0 : 1;
            rst.maxval = MAX_LIMIT;
          }
          else
          {
            rst.minval = bl_minval;
            rst.maxval = bl_maxval;
          }

          /*
		 * When maxval > minval, try matching as much as possible, up
		 * to maxval.  When maxval < minval, try matching at least the
		 * minimal number (since the range is backwards, that's also
		 * maxval!).
		 */
          rst.count = regrepeat(OPERAND(scan), rst.maxval);
          if (got_int)
          {
            status = RA_FAIL;
            break;
          }
          if (rst.minval <= rst.maxval
                  ? rst.count >= rst.minval
                  : rst.count >= rst.maxval)
          {
            /* It could match.  Prepare for trying to match what
		     * follows.  The code is below.  Parameters are stored in
		     * a regstar_T on the regstack. */
            if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
            {
              emsg(_(e_maxmempat));
              status = RA_FAIL;
            }
            else if (ga_grow(&regstack, sizeof(regstar_T)) == FAIL)
              status = RA_FAIL;
            else
            {
              regstack.ga_len += sizeof(regstar_T);
              rp = regstack_push(rst.minval <= rst.maxval
                                     ? RS_STAR_LONG
                                     : RS_STAR_SHORT,
                                 scan);
              if (rp == NULL)
                status = RA_FAIL;
              else
              {
                *(((regstar_T *)rp) - 1) = rst;
                status = RA_BREAK; /* skip the restore bits */
              }
            }
          }
          else
            status = RA_NOMATCH;
        }
        break;

        case NOMATCH:
        case MATCH:
        case SUBPAT:
          rp = regstack_push(RS_NOMATCH, scan);
          if (rp == NULL)
            status = RA_FAIL;
          else
          {
            rp->rs_no = op;
            reg_save(&rp->rs_un.regsave, &backpos);
            next = OPERAND(scan);
            /* We continue and handle the result when done. */
          }
          break;

        case BEHIND:
        case NOBEHIND:
          /* Need a bit of room to store extra positions. */
          if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
          {
            emsg(_(e_maxmempat));
            status = RA_FAIL;
          }
          else if (ga_grow(&regstack, sizeof(regbehind_T)) == FAIL)
            status = RA_FAIL;
          else
          {
            regstack.ga_len += sizeof(regbehind_T);
            rp = regstack_push(RS_BEHIND1, scan);
            if (rp == NULL)
              status = RA_FAIL;
            else
            {
              /* Need to save the subexpr to be able to restore them
		     * when there is a match but we don't use it. */
              save_subexpr(((regbehind_T *)rp) - 1);

              rp->rs_no = op;
              reg_save(&rp->rs_un.regsave, &backpos);
              /* First try if what follows matches.  If it does then we
		     * check the behind match by looping. */
            }
          }
          break;

        case BHPOS:
          if (REG_MULTI)
          {
            if (behind_pos.rs_u.pos.col != (colnr_T)(rex.input - rex.line) || behind_pos.rs_u.pos.lnum != rex.lnum)
              status = RA_NOMATCH;
          }
          else if (behind_pos.rs_u.ptr != rex.input)
            status = RA_NOMATCH;
          break;

        case NEWL:
          if ((c != NUL || !REG_MULTI || rex.lnum > rex.reg_maxline || rex.reg_line_lbr) && (c != '\n' || !rex.reg_line_lbr))
            status = RA_NOMATCH;
          else if (rex.reg_line_lbr)
            ADVANCE_REGINPUT();
          else
            reg_nextline();
          break;

        case END:
          status = RA_MATCH; /* Success! */
          break;

        default:
          emsg(_(e_re_corr));
#ifdef DEBUG
          printf("Illegal op code %d\n", op);
#endif
          status = RA_FAIL;
          break;
        }
      }

      /* If we can't continue sequentially, break the inner loop. */
      if (status != RA_CONT)
        break;

      /* Continue in inner loop, advance to next item. */
      scan = next;

    } /* end of inner loop */

    /*
     * If there is something on the regstack execute the code for the state.
     * If the state is popped then loop and use the older state.
     */
    while (regstack.ga_len > 0 && status != RA_FAIL)
    {
      rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
      switch (rp->rs_state)
      {
      case RS_NOPEN:
        /* Result is passed on as-is, simply pop the state. */
        regstack_pop(&scan);
        break;

      case RS_MOPEN:
        /* Pop the state.  Restore pointers when there is no match. */
        if (status == RA_NOMATCH)
          restore_se(&rp->rs_un.sesave, &rex.reg_startpos[rp->rs_no],
                     &rex.reg_startp[rp->rs_no]);
        regstack_pop(&scan);
        break;

      case RS_MCLOSE:
        /* Pop the state.  Restore pointers when there is no match. */
        if (status == RA_NOMATCH)
          restore_se(&rp->rs_un.sesave, &rex.reg_endpos[rp->rs_no],
                     &rex.reg_endp[rp->rs_no]);
        regstack_pop(&scan);
        break;

      case RS_BRANCH:
        if (status == RA_MATCH)
          /* this branch matched, use it */
          regstack_pop(&scan);
        else
        {
          if (status != RA_BREAK)
          {
            /* After a non-matching branch: try next one. */
            reg_restore(&rp->rs_un.regsave, &backpos);
            scan = rp->rs_scan;
          }
          if (scan == NULL || OP(scan) != BRANCH)
          {
            /* no more branches, didn't find a match */
            status = RA_NOMATCH;
            regstack_pop(&scan);
          }
          else
          {
            /* Prepare to try a branch. */
            rp->rs_scan = regnext(scan);
            reg_save(&rp->rs_un.regsave, &backpos);
            scan = OPERAND(scan);
          }
        }
        break;

      case RS_BRCPLX_MORE:
        /* Pop the state.  Restore pointers when there is no match. */
        if (status == RA_NOMATCH)
        {
          reg_restore(&rp->rs_un.regsave, &backpos);
          --brace_count[rp->rs_no]; /* decrement match count */
        }
        regstack_pop(&scan);
        break;

      case RS_BRCPLX_LONG:
        /* Pop the state.  Restore pointers when there is no match. */
        if (status == RA_NOMATCH)
        {
          /* There was no match, but we did find enough matches. */
          reg_restore(&rp->rs_un.regsave, &backpos);
          --brace_count[rp->rs_no];
          /* continue with the items after "\{}" */
          status = RA_CONT;
        }
        regstack_pop(&scan);
        if (status == RA_CONT)
          scan = regnext(scan);
        break;

      case RS_BRCPLX_SHORT:
        /* Pop the state.  Restore pointers when there is no match. */
        if (status == RA_NOMATCH)
          /* There was no match, try to match one more item. */
          reg_restore(&rp->rs_un.regsave, &backpos);
        regstack_pop(&scan);
        if (status == RA_NOMATCH)
        {
          scan = OPERAND(scan);
          status = RA_CONT;
        }
        break;

      case RS_NOMATCH:
        /* Pop the state.  If the operand matches for NOMATCH or
	     * doesn't match for MATCH/SUBPAT, we fail.  Otherwise backup,
	     * except for SUBPAT, and continue with the next item. */
        if (status == (rp->rs_no == NOMATCH ? RA_MATCH : RA_NOMATCH))
          status = RA_NOMATCH;
        else
        {
          status = RA_CONT;
          if (rp->rs_no != SUBPAT) /* zero-width */
            reg_restore(&rp->rs_un.regsave, &backpos);
        }
        regstack_pop(&scan);
        if (status == RA_CONT)
          scan = regnext(scan);
        break;

      case RS_BEHIND1:
        if (status == RA_NOMATCH)
        {
          regstack_pop(&scan);
          regstack.ga_len -= sizeof(regbehind_T);
        }
        else
        {
          /* The stuff after BEHIND/NOBEHIND matches.  Now try if
		 * the behind part does (not) match before the current
		 * position in the input.  This must be done at every
		 * position in the input and checking if the match ends at
		 * the current position. */

          /* save the position after the found match for next */
          reg_save(&(((regbehind_T *)rp) - 1)->save_after, &backpos);

          /* Start looking for a match with operand at the current
		 * position.  Go back one character until we find the
		 * result, hitting the start of the line or the previous
		 * line (for multi-line matching).
		 * Set behind_pos to where the match should end, BHPOS
		 * will match it.  Save the current value. */
          (((regbehind_T *)rp) - 1)->save_behind = behind_pos;
          behind_pos = rp->rs_un.regsave;

          rp->rs_state = RS_BEHIND2;

          reg_restore(&rp->rs_un.regsave, &backpos);
          scan = OPERAND(rp->rs_scan) + 4;
        }
        break;

      case RS_BEHIND2:
        /*
	     * Looping for BEHIND / NOBEHIND match.
	     */
        if (status == RA_MATCH && reg_save_equal(&behind_pos))
        {
          /* found a match that ends where "next" started */
          behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
          if (rp->rs_no == BEHIND)
            reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
                        &backpos);
          else
          {
            /* But we didn't want a match.  Need to restore the
		     * subexpr, because what follows matched, so they have
		     * been set. */
            status = RA_NOMATCH;
            restore_subexpr(((regbehind_T *)rp) - 1);
          }
          regstack_pop(&scan);
          regstack.ga_len -= sizeof(regbehind_T);
        }
        else
        {
          long limit;

          /* No match or a match that doesn't end where we want it: Go
		 * back one character.  May go to previous line once. */
          no = OK;
          limit = OPERAND_MIN(rp->rs_scan);
          if (REG_MULTI)
          {
            if (limit > 0 && ((rp->rs_un.regsave.rs_u.pos.lnum < behind_pos.rs_u.pos.lnum
                                   ? (colnr_T)STRLEN(rex.line)
                                   : behind_pos.rs_u.pos.col) -
                                  rp->rs_un.regsave.rs_u.pos.col >=
                              limit))
              no = FAIL;
            else if (rp->rs_un.regsave.rs_u.pos.col == 0)
            {
              if (rp->rs_un.regsave.rs_u.pos.lnum < behind_pos.rs_u.pos.lnum || reg_getline(
                                                                                    --rp->rs_un.regsave.rs_u.pos.lnum) == NULL)
                no = FAIL;
              else
              {
                reg_restore(&rp->rs_un.regsave, &backpos);
                rp->rs_un.regsave.rs_u.pos.col =
                    (colnr_T)STRLEN(rex.line);
              }
            }
            else
            {
              if (has_mbyte)
              {
                char_u *line =
                    reg_getline(rp->rs_un.regsave.rs_u.pos.lnum);

                rp->rs_un.regsave.rs_u.pos.col -=
                    (*mb_head_off)(line, line + rp->rs_un.regsave.rs_u.pos.col - 1) + 1;
              }
              else
                --rp->rs_un.regsave.rs_u.pos.col;
            }
          }
          else
          {
            if (rp->rs_un.regsave.rs_u.ptr == rex.line)
              no = FAIL;
            else
            {
              MB_PTR_BACK(rex.line, rp->rs_un.regsave.rs_u.ptr);
              if (limit > 0 && (long)(behind_pos.rs_u.ptr - rp->rs_un.regsave.rs_u.ptr) > limit)
                no = FAIL;
            }
          }
          if (no == OK)
          {
            /* Advanced, prepare for finding match again. */
            reg_restore(&rp->rs_un.regsave, &backpos);
            scan = OPERAND(rp->rs_scan) + 4;
            if (status == RA_MATCH)
            {
              /* We did match, so subexpr may have been changed,
			 * need to restore them for the next try. */
              status = RA_NOMATCH;
              restore_subexpr(((regbehind_T *)rp) - 1);
            }
          }
          else
          {
            /* Can't advance.  For NOBEHIND that's a match. */
            behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
            if (rp->rs_no == NOBEHIND)
            {
              reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
                          &backpos);
              status = RA_MATCH;
            }
            else
            {
              /* We do want a proper match.  Need to restore the
			 * subexpr if we had a match, because they may have
			 * been set. */
              if (status == RA_MATCH)
              {
                status = RA_NOMATCH;
                restore_subexpr(((regbehind_T *)rp) - 1);
              }
            }
            regstack_pop(&scan);
            regstack.ga_len -= sizeof(regbehind_T);
          }
        }
        break;

      case RS_STAR_LONG:
      case RS_STAR_SHORT:
      {
        regstar_T *rst = ((regstar_T *)rp) - 1;

        if (status == RA_MATCH)
        {
          regstack_pop(&scan);
          regstack.ga_len -= sizeof(regstar_T);
          break;
        }

        /* Tried once already, restore input pointers. */
        if (status != RA_BREAK)
          reg_restore(&rp->rs_un.regsave, &backpos);

        /* Repeat until we found a position where it could match. */
        for (;;)
        {
          if (status != RA_BREAK)
          {
            /* Tried first position already, advance. */
            if (rp->rs_state == RS_STAR_LONG)
            {
              /* Trying for longest match, but couldn't or
			     * didn't match -- back up one char. */
              if (--rst->count < rst->minval)
                break;
              if (rex.input == rex.line)
              {
                /* backup to last char of previous line */
                --rex.lnum;
                rex.line = reg_getline(rex.lnum);
                /* Just in case regrepeat() didn't count
				 * right. */
                if (rex.line == NULL)
                  break;
                rex.input = rex.line + STRLEN(rex.line);
                fast_breakcheck();
              }
              else
                MB_PTR_BACK(rex.line, rex.input);
            }
            else
            {
              /* Range is backwards, use shortest match first.
			     * Careful: maxval and minval are exchanged!
			     * Couldn't or didn't match: try advancing one
			     * char. */
              if (rst->count == rst->minval || regrepeat(OPERAND(rp->rs_scan), 1L) == 0)
                break;
              ++rst->count;
            }
            if (got_int)
              break;
          }
          else
            status = RA_NOMATCH;

          /* If it could match, try it. */
          if (rst->nextb == NUL || *rex.input == rst->nextb || *rex.input == rst->nextb_ic)
          {
            reg_save(&rp->rs_un.regsave, &backpos);
            scan = regnext(rp->rs_scan);
            status = RA_CONT;
            break;
          }
        }
        if (status != RA_CONT)
        {
          /* Failed. */
          regstack_pop(&scan);
          regstack.ga_len -= sizeof(regstar_T);
          status = RA_NOMATCH;
        }
      }
      break;
      }

      /* If we want to continue the inner loop or didn't pop a state
	 * continue matching loop */
      if (status == RA_CONT || rp == (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1)
        break;
    }

    /* May need to continue with the inner loop, starting at "scan". */
    if (status == RA_CONT)
      continue;

    /*
     * If the regstack is empty or something failed we are done.
     */
    if (regstack.ga_len == 0 || status == RA_FAIL)
    {
      if (scan == NULL)
      {
        /*
	     * We get here only if there's trouble -- normally "case END" is
	     * the terminating point.
	     */
        emsg(_(e_re_corr));
#ifdef DEBUG
        printf("Premature EOL\n");
#endif
      }
      return (status == RA_MATCH);
    }

  } /* End of loop until the regstack is empty. */

  /* NOTREACHED */
}

/*
 * Push an item onto the regstack.
 * Returns pointer to new item.  Returns NULL when out of memory.
 */
static regitem_T *
regstack_push(regstate_T state, char_u *scan)
{
  regitem_T *rp;

  if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
  {
    emsg(_(e_maxmempat));
    return NULL;
  }
  if (ga_grow(&regstack, sizeof(regitem_T)) == FAIL)
    return NULL;

  rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len);
  rp->rs_state = state;
  rp->rs_scan = scan;

  regstack.ga_len += sizeof(regitem_T);
  return rp;
}

/*
 * Pop an item from the regstack.
 */
static void
regstack_pop(char_u **scan)
{
  regitem_T *rp;

  rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
  *scan = rp->rs_scan;

  regstack.ga_len -= sizeof(regitem_T);
}

/*
 * regrepeat - repeatedly match something simple, return how many.
 * Advances rex.input (and rex.lnum) to just after the matched chars.
 */
static int
regrepeat(
    char_u *p,
    long maxcount) /* maximum number of matches allowed */
{
  long count = 0;
  char_u *scan;
  char_u *opnd;
  int mask;
  int testval = 0;

  scan = rex.input; /* Make local copy of rex.input for speed. */
  opnd = OPERAND(p);
  switch (OP(p))
  {
  case ANY:
  case ANY + ADD_NL:
    while (count < maxcount)
    {
      /* Matching anything means we continue until end-of-line (or
	     * end-of-file for ANY + ADD_NL), only limited by maxcount. */
      while (*scan != NUL && count < maxcount)
      {
        ++count;
        MB_PTR_ADV(scan);
      }
      if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr || count == maxcount)
        break;
      ++count; /* count the line-break */
      reg_nextline();
      scan = rex.input;
      if (got_int)
        break;
    }
    break;

  case IDENT:
  case IDENT + ADD_NL:
    testval = TRUE;
    /* FALLTHROUGH */
  case SIDENT:
  case SIDENT + ADD_NL:
    while (count < maxcount)
    {
      if (vim_isIDc(PTR2CHAR(scan)) && (testval || !VIM_ISDIGIT(*scan)))
      {
        MB_PTR_ADV(scan);
      }
      else if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else
        break;
      ++count;
    }
    break;

  case KWORD:
  case KWORD + ADD_NL:
    testval = TRUE;
    /* FALLTHROUGH */
  case SKWORD:
  case SKWORD + ADD_NL:
    while (count < maxcount)
    {
      if (vim_iswordp_buf(scan, rex.reg_buf) && (testval || !VIM_ISDIGIT(*scan)))
      {
        MB_PTR_ADV(scan);
      }
      else if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else
        break;
      ++count;
    }
    break;

  case FNAME:
  case FNAME + ADD_NL:
    testval = TRUE;
    /* FALLTHROUGH */
  case SFNAME:
  case SFNAME + ADD_NL:
    while (count < maxcount)
    {
      if (vim_isfilec(PTR2CHAR(scan)) && (testval || !VIM_ISDIGIT(*scan)))
      {
        MB_PTR_ADV(scan);
      }
      else if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else
        break;
      ++count;
    }
    break;

  case PRINT:
  case PRINT + ADD_NL:
    testval = TRUE;
    /* FALLTHROUGH */
  case SPRINT:
  case SPRINT + ADD_NL:
    while (count < maxcount)
    {
      if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (vim_isprintc(PTR2CHAR(scan)) == 1 && (testval || !VIM_ISDIGIT(*scan)))
      {
        MB_PTR_ADV(scan);
      }
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else
        break;
      ++count;
    }
    break;

  case WHITE:
  case WHITE + ADD_NL:
    testval = mask = RI_WHITE;
  do_class:
    while (count < maxcount)
    {
      int l;

      if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (has_mbyte && (l = (*mb_ptr2len)(scan)) > 1)
      {
        if (testval != 0)
          break;
        scan += l;
      }
      else if ((class_tab[*scan] & mask) == testval)
        ++scan;
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else
        break;
      ++count;
    }
    break;

  case NWHITE:
  case NWHITE + ADD_NL:
    mask = RI_WHITE;
    goto do_class;
  case DIGIT:
  case DIGIT + ADD_NL:
    testval = mask = RI_DIGIT;
    goto do_class;
  case NDIGIT:
  case NDIGIT + ADD_NL:
    mask = RI_DIGIT;
    goto do_class;
  case HEX:
  case HEX + ADD_NL:
    testval = mask = RI_HEX;
    goto do_class;
  case NHEX:
  case NHEX + ADD_NL:
    mask = RI_HEX;
    goto do_class;
  case OCTAL:
  case OCTAL + ADD_NL:
    testval = mask = RI_OCTAL;
    goto do_class;
  case NOCTAL:
  case NOCTAL + ADD_NL:
    mask = RI_OCTAL;
    goto do_class;
  case WORD:
  case WORD + ADD_NL:
    testval = mask = RI_WORD;
    goto do_class;
  case NWORD:
  case NWORD + ADD_NL:
    mask = RI_WORD;
    goto do_class;
  case HEAD:
  case HEAD + ADD_NL:
    testval = mask = RI_HEAD;
    goto do_class;
  case NHEAD:
  case NHEAD + ADD_NL:
    mask = RI_HEAD;
    goto do_class;
  case ALPHA:
  case ALPHA + ADD_NL:
    testval = mask = RI_ALPHA;
    goto do_class;
  case NALPHA:
  case NALPHA + ADD_NL:
    mask = RI_ALPHA;
    goto do_class;
  case LOWER:
  case LOWER + ADD_NL:
    testval = mask = RI_LOWER;
    goto do_class;
  case NLOWER:
  case NLOWER + ADD_NL:
    mask = RI_LOWER;
    goto do_class;
  case UPPER:
  case UPPER + ADD_NL:
    testval = mask = RI_UPPER;
    goto do_class;
  case NUPPER:
  case NUPPER + ADD_NL:
    mask = RI_UPPER;
    goto do_class;

  case EXACTLY:
  {
    int cu, cl;

    /* This doesn't do a multi-byte character, because a MULTIBYTECODE
	     * would have been used for it.  It does handle single-byte
	     * characters, such as latin1. */
    if (rex.reg_ic)
    {
      cu = MB_TOUPPER(*opnd);
      cl = MB_TOLOWER(*opnd);
      while (count < maxcount && (*scan == cu || *scan == cl))
      {
        count++;
        scan++;
      }
    }
    else
    {
      cu = *opnd;
      while (count < maxcount && *scan == cu)
      {
        count++;
        scan++;
      }
    }
    break;
  }

  case MULTIBYTECODE:
  {
    int i, len, cf = 0;

    /* Safety check (just in case 'encoding' was changed since
	     * compiling the program). */
    if ((len = (*mb_ptr2len)(opnd)) > 1)
    {
      if (rex.reg_ic && enc_utf8)
        cf = utf_fold(utf_ptr2char(opnd));
      while (count < maxcount && (*mb_ptr2len)(scan) >= len)
      {
        for (i = 0; i < len; ++i)
          if (opnd[i] != scan[i])
            break;
        if (i < len && (!rex.reg_ic || !enc_utf8 || utf_fold(utf_ptr2char(scan)) != cf))
          break;
        scan += len;
        ++count;
      }
    }
  }
  break;

  case ANYOF:
  case ANYOF + ADD_NL:
    testval = TRUE;
    /* FALLTHROUGH */

  case ANYBUT:
  case ANYBUT + ADD_NL:
    while (count < maxcount)
    {
      int len;

      if (*scan == NUL)
      {
        if (!REG_MULTI || !WITH_NL(OP(p)) || rex.lnum > rex.reg_maxline || rex.reg_line_lbr)
          break;
        reg_nextline();
        scan = rex.input;
        if (got_int)
          break;
      }
      else if (rex.reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
        ++scan;
      else if (has_mbyte && (len = (*mb_ptr2len)(scan)) > 1)
      {
        if ((cstrchr(opnd, (*mb_ptr2char)(scan)) == NULL) == testval)
          break;
        scan += len;
      }
      else
      {
        if ((cstrchr(opnd, *scan) == NULL) == testval)
          break;
        ++scan;
      }
      ++count;
    }
    break;

  case NEWL:
    while (count < maxcount && ((*scan == NUL && rex.lnum <= rex.reg_maxline && !rex.reg_line_lbr && REG_MULTI) || (*scan == '\n' && rex.reg_line_lbr)))
    {
      count++;
      if (rex.reg_line_lbr)
        ADVANCE_REGINPUT();
      else
        reg_nextline();
      scan = rex.input;
      if (got_int)
        break;
    }
    break;

  default: /* Oh dear.  Called inappropriately. */
    emsg(_(e_re_corr));
#ifdef DEBUG
    printf("Called regrepeat with op code %d\n", OP(p));
#endif
    break;
  }

  rex.input = scan;

  return (int)count;
}

/*
 * regnext - dig the "next" pointer out of a node
 * Returns NULL when calculating size, when there is no next item and when
 * there is an error.
 */
static char_u *
regnext(char_u *p)
{
  int offset;

  if (p == JUST_CALC_SIZE || reg_toolong)
    return NULL;

  offset = NEXT(p);
  if (offset == 0)
    return NULL;

  if (OP(p) == BACK)
    return p - offset;
  else
    return p + offset;
}

/*
 * Check the regexp program for its magic number.
 * Return TRUE if it's wrong.
 */
static int
prog_magic_wrong(void)
{
  regprog_T *prog;

  prog = REG_MULTI ? rex.reg_mmatch->regprog : rex.reg_match->regprog;
  if (prog->engine == &nfa_regengine)
    /* For NFA matcher we don't check the magic */
    return FALSE;

  if (UCHARAT(((bt_regprog_T *)prog)->program) != REGMAGIC)
  {
    emsg(_(e_re_corr));
    return TRUE;
  }
  return FALSE;
}

/*
 * Cleanup the subexpressions, if this wasn't done yet.
 * This construction is used to clear the subexpressions only when they are
 * used (to increase speed).
 */
static void
cleanup_subexpr(void)
{
  if (rex.need_clear_subexpr)
  {
    if (REG_MULTI)
    {
      /* Use 0xff to set lnum to -1 */
      vim_memset(rex.reg_startpos, 0xff, sizeof(lpos_T) * NSUBEXP);
      vim_memset(rex.reg_endpos, 0xff, sizeof(lpos_T) * NSUBEXP);
    }
    else
    {
      vim_memset(rex.reg_startp, 0, sizeof(char_u *) * NSUBEXP);
      vim_memset(rex.reg_endp, 0, sizeof(char_u *) * NSUBEXP);
    }
    rex.need_clear_subexpr = FALSE;
  }
}

/*
 * Save the current subexpr to "bp", so that they can be restored
 * later by restore_subexpr().
 */
static void
save_subexpr(regbehind_T *bp)
{
  int i;

  /* When "rex.need_clear_subexpr" is set we don't need to save the values, only
     * remember that this flag needs to be set again when restoring. */
  bp->save_need_clear_subexpr = rex.need_clear_subexpr;
  if (!rex.need_clear_subexpr)
  {
    for (i = 0; i < NSUBEXP; ++i)
    {
      if (REG_MULTI)
      {
        bp->save_start[i].se_u.pos = rex.reg_startpos[i];
        bp->save_end[i].se_u.pos = rex.reg_endpos[i];
      }
      else
      {
        bp->save_start[i].se_u.ptr = rex.reg_startp[i];
        bp->save_end[i].se_u.ptr = rex.reg_endp[i];
      }
    }
  }
}

/*
 * Restore the subexpr from "bp".
 */
static void
restore_subexpr(regbehind_T *bp)
{
  int i;

  /* Only need to restore saved values when they are not to be cleared. */
  rex.need_clear_subexpr = bp->save_need_clear_subexpr;
  if (!rex.need_clear_subexpr)
  {
    for (i = 0; i < NSUBEXP; ++i)
    {
      if (REG_MULTI)
      {
        rex.reg_startpos[i] = bp->save_start[i].se_u.pos;
        rex.reg_endpos[i] = bp->save_end[i].se_u.pos;
      }
      else
      {
        rex.reg_startp[i] = bp->save_start[i].se_u.ptr;
        rex.reg_endp[i] = bp->save_end[i].se_u.ptr;
      }
    }
  }
}

/*
 * Advance rex.lnum, rex.line and rex.input to the next line.
 */
static void
reg_nextline(void)
{
  rex.line = reg_getline(++rex.lnum);
  rex.input = rex.line;
  fast_breakcheck();
}

/*
 * Save the input line and position in a regsave_T.
 */
static void
reg_save(regsave_T *save, garray_T *gap)
{
  if (REG_MULTI)
  {
    save->rs_u.pos.col = (colnr_T)(rex.input - rex.line);
    save->rs_u.pos.lnum = rex.lnum;
  }
  else
    save->rs_u.ptr = rex.input;
  save->rs_len = gap->ga_len;
}

/*
 * Restore the input line and position from a regsave_T.
 */
static void
reg_restore(regsave_T *save, garray_T *gap)
{
  if (REG_MULTI)
  {
    if (rex.lnum != save->rs_u.pos.lnum)
    {
      /* only call reg_getline() when the line number changed to save
	     * a bit of time */
      rex.lnum = save->rs_u.pos.lnum;
      rex.line = reg_getline(rex.lnum);
    }
    rex.input = rex.line + save->rs_u.pos.col;
  }
  else
    rex.input = save->rs_u.ptr;
  gap->ga_len = save->rs_len;
}

/*
 * Return TRUE if current position is equal to saved position.
 */
static int
reg_save_equal(regsave_T *save)
{
  if (REG_MULTI)
    return rex.lnum == save->rs_u.pos.lnum && rex.input == rex.line + save->rs_u.pos.col;
  return rex.input == save->rs_u.ptr;
}

/*
 * Tentatively set the sub-expression start to the current position (after
 * calling regmatch() they will have changed).  Need to save the existing
 * values for when there is no match.
 * Use se_save() to use pointer (save_se_multi()) or position (save_se_one()),
 * depending on REG_MULTI.
 */
static void
save_se_multi(save_se_T *savep, lpos_T *posp)
{
  savep->se_u.pos = *posp;
  posp->lnum = rex.lnum;
  posp->col = (colnr_T)(rex.input - rex.line);
}

static void
save_se_one(save_se_T *savep, char_u **pp)
{
  savep->se_u.ptr = *pp;
  *pp = rex.input;
}

/*
 * Compare a number with the operand of RE_LNUM, RE_COL or RE_VCOL.
 */
static int
re_num_cmp(long_u val, char_u *scan)
{
  long_u n = OPERAND_MIN(scan);

  if (OPERAND_CMP(scan) == '>')
    return val > n;
  if (OPERAND_CMP(scan) == '<')
    return val < n;
  return val == n;
}

/*
 * Check whether a backreference matches.
 * Returns RA_FAIL, RA_NOMATCH or RA_MATCH.
 * If "bytelen" is not NULL, it is set to the byte length of the match in the
 * last line.
 */
static int
match_with_backref(
    linenr_T start_lnum,
    colnr_T start_col,
    linenr_T end_lnum,
    colnr_T end_col,
    int *bytelen)
{
  linenr_T clnum = start_lnum;
  colnr_T ccol = start_col;
  int len;
  char_u *p;

  if (bytelen != NULL)
    *bytelen = 0;
  for (;;)
  {
    /* Since getting one line may invalidate the other, need to make copy.
	 * Slow! */
    if (rex.line != reg_tofree)
    {
      len = (int)STRLEN(rex.line);
      if (reg_tofree == NULL || len >= (int)reg_tofreelen)
      {
        len += 50; /* get some extra */
        vim_free(reg_tofree);
        reg_tofree = alloc(len);
        if (reg_tofree == NULL)
          return RA_FAIL; /* out of memory!*/
        reg_tofreelen = len;
      }
      STRCPY(reg_tofree, rex.line);
      rex.input = reg_tofree + (rex.input - rex.line);
      rex.line = reg_tofree;
    }

    /* Get the line to compare with. */
    p = reg_getline(clnum);
    if (clnum == end_lnum)
      len = end_col - ccol;
    else
      len = (int)STRLEN(p + ccol);

    if (cstrncmp(p + ccol, rex.input, &len) != 0)
      return RA_NOMATCH; /* doesn't match */
    if (bytelen != NULL)
      *bytelen += len;
    if (clnum == end_lnum)
      break; /* match and at end! */
    if (rex.lnum >= rex.reg_maxline)
      return RA_NOMATCH; /* text too short */

    /* Advance to next line. */
    reg_nextline();
    if (bytelen != NULL)
      *bytelen = 0;
    ++clnum;
    ccol = 0;
    if (got_int)
      return RA_FAIL;
  }

  /* found a match!  Note that rex.line may now point to a copy of the line,
     * that should not matter. */
  return RA_MATCH;
}

#ifdef BT_REGEXP_DUMP

/*
 * regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
static void
regdump(char_u *pattern, bt_regprog_T *r)
{
  char_u *s;
  int op = EXACTLY; /* Arbitrary non-END op. */
  char_u *next;
  char_u *end = NULL;
  FILE *f;

#ifdef BT_REGEXP_LOG
  f = fopen("bt_regexp_log.log", "a");
#else
  f = stdout;
#endif
  if (f == NULL)
    return;
  fprintf(f, "-------------------------------------\n\r\nregcomp(%s):\r\n", pattern);

  s = r->program + 1;
  /*
     * Loop until we find the END that isn't before a referred next (an END
     * can also appear in a NOMATCH operand).
     */
  while (op != END || s <= end)
  {
    op = OP(s);
    fprintf(f, "%2d%s", (int)(s - r->program), regprop(s)); /* Where, what. */
    next = regnext(s);
    if (next == NULL) /* Next ptr. */
      fprintf(f, "(0)");
    else
      fprintf(f, "(%d)", (int)((s - r->program) + (next - s)));
    if (end < next)
      end = next;
    if (op == BRACE_LIMITS)
    {
      /* Two ints */
      fprintf(f, " minval %ld, maxval %ld", OPERAND_MIN(s), OPERAND_MAX(s));
      s += 8;
    }
    else if (op == BEHIND || op == NOBEHIND)
    {
      /* one int */
      fprintf(f, " count %ld", OPERAND_MIN(s));
      s += 4;
    }
    else if (op == RE_LNUM || op == RE_COL || op == RE_VCOL)
    {
      /* one int plus comparator */
      fprintf(f, " count %ld", OPERAND_MIN(s));
      s += 5;
    }
    s += 3;
    if (op == ANYOF || op == ANYOF + ADD_NL || op == ANYBUT || op == ANYBUT + ADD_NL || op == EXACTLY)
    {
      /* Literal string, where present. */
      fprintf(f, "\nxxxxxxxxx\n");
      while (*s != NUL)
        fprintf(f, "%c", *s++);
      fprintf(f, "\nxxxxxxxxx\n");
      s++;
    }
    fprintf(f, "\r\n");
  }

  /* Header fields of interest. */
  if (r->regstart != NUL)
    fprintf(f, "start `%s' 0x%x; ", r->regstart < 256 ? (char *)transchar(r->regstart) : "multibyte", r->regstart);
  if (r->reganch)
    fprintf(f, "anchored; ");
  if (r->regmust != NULL)
    fprintf(f, "must have \"%s\"", r->regmust);
  fprintf(f, "\r\n");

#ifdef BT_REGEXP_LOG
  fclose(f);
#endif
}
#endif /* BT_REGEXP_DUMP */

#ifdef DEBUG
/*
 * regprop - printable representation of opcode
 */
static char_u *
regprop(char_u *op)
{
  char *p;
  static char buf[50];

  STRCPY(buf, ":");

  switch ((int)OP(op))
  {
  case BOL:
    p = "BOL";
    break;
  case EOL:
    p = "EOL";
    break;
  case RE_BOF:
    p = "BOF";
    break;
  case RE_EOF:
    p = "EOF";
    break;
  case CURSOR:
    p = "CURSOR";
    break;
  case RE_VISUAL:
    p = "RE_VISUAL";
    break;
  case RE_LNUM:
    p = "RE_LNUM";
    break;
  case RE_MARK:
    p = "RE_MARK";
    break;
  case RE_COL:
    p = "RE_COL";
    break;
  case RE_VCOL:
    p = "RE_VCOL";
    break;
  case BOW:
    p = "BOW";
    break;
  case EOW:
    p = "EOW";
    break;
  case ANY:
    p = "ANY";
    break;
  case ANY + ADD_NL:
    p = "ANY+NL";
    break;
  case ANYOF:
    p = "ANYOF";
    break;
  case ANYOF + ADD_NL:
    p = "ANYOF+NL";
    break;
  case ANYBUT:
    p = "ANYBUT";
    break;
  case ANYBUT + ADD_NL:
    p = "ANYBUT+NL";
    break;
  case IDENT:
    p = "IDENT";
    break;
  case IDENT + ADD_NL:
    p = "IDENT+NL";
    break;
  case SIDENT:
    p = "SIDENT";
    break;
  case SIDENT + ADD_NL:
    p = "SIDENT+NL";
    break;
  case KWORD:
    p = "KWORD";
    break;
  case KWORD + ADD_NL:
    p = "KWORD+NL";
    break;
  case SKWORD:
    p = "SKWORD";
    break;
  case SKWORD + ADD_NL:
    p = "SKWORD+NL";
    break;
  case FNAME:
    p = "FNAME";
    break;
  case FNAME + ADD_NL:
    p = "FNAME+NL";
    break;
  case SFNAME:
    p = "SFNAME";
    break;
  case SFNAME + ADD_NL:
    p = "SFNAME+NL";
    break;
  case PRINT:
    p = "PRINT";
    break;
  case PRINT + ADD_NL:
    p = "PRINT+NL";
    break;
  case SPRINT:
    p = "SPRINT";
    break;
  case SPRINT + ADD_NL:
    p = "SPRINT+NL";
    break;
  case WHITE:
    p = "WHITE";
    break;
  case WHITE + ADD_NL:
    p = "WHITE+NL";
    break;
  case NWHITE:
    p = "NWHITE";
    break;
  case NWHITE + ADD_NL:
    p = "NWHITE+NL";
    break;
  case DIGIT:
    p = "DIGIT";
    break;
  case DIGIT + ADD_NL:
    p = "DIGIT+NL";
    break;
  case NDIGIT:
    p = "NDIGIT";
    break;
  case NDIGIT + ADD_NL:
    p = "NDIGIT+NL";
    break;
  case HEX:
    p = "HEX";
    break;
  case HEX + ADD_NL:
    p = "HEX+NL";
    break;
  case NHEX:
    p = "NHEX";
    break;
  case NHEX + ADD_NL:
    p = "NHEX+NL";
    break;
  case OCTAL:
    p = "OCTAL";
    break;
  case OCTAL + ADD_NL:
    p = "OCTAL+NL";
    break;
  case NOCTAL:
    p = "NOCTAL";
    break;
  case NOCTAL + ADD_NL:
    p = "NOCTAL+NL";
    break;
  case WORD:
    p = "WORD";
    break;
  case WORD + ADD_NL:
    p = "WORD+NL";
    break;
  case NWORD:
    p = "NWORD";
    break;
  case NWORD + ADD_NL:
    p = "NWORD+NL";
    break;
  case HEAD:
    p = "HEAD";
    break;
  case HEAD + ADD_NL:
    p = "HEAD+NL";
    break;
  case NHEAD:
    p = "NHEAD";
    break;
  case NHEAD + ADD_NL:
    p = "NHEAD+NL";
    break;
  case ALPHA:
    p = "ALPHA";
    break;
  case ALPHA + ADD_NL:
    p = "ALPHA+NL";
    break;
  case NALPHA:
    p = "NALPHA";
    break;
  case NALPHA + ADD_NL:
    p = "NALPHA+NL";
    break;
  case LOWER:
    p = "LOWER";
    break;
  case LOWER + ADD_NL:
    p = "LOWER+NL";
    break;
  case NLOWER:
    p = "NLOWER";
    break;
  case NLOWER + ADD_NL:
    p = "NLOWER+NL";
    break;
  case UPPER:
    p = "UPPER";
    break;
  case UPPER + ADD_NL:
    p = "UPPER+NL";
    break;
  case NUPPER:
    p = "NUPPER";
    break;
  case NUPPER + ADD_NL:
    p = "NUPPER+NL";
    break;
  case BRANCH:
    p = "BRANCH";
    break;
  case EXACTLY:
    p = "EXACTLY";
    break;
  case NOTHING:
    p = "NOTHING";
    break;
  case BACK:
    p = "BACK";
    break;
  case END:
    p = "END";
    break;
  case MOPEN + 0:
    p = "MATCH START";
    break;
  case MOPEN + 1:
  case MOPEN + 2:
  case MOPEN + 3:
  case MOPEN + 4:
  case MOPEN + 5:
  case MOPEN + 6:
  case MOPEN + 7:
  case MOPEN + 8:
  case MOPEN + 9:
    sprintf(buf + STRLEN(buf), "MOPEN%d", OP(op) - MOPEN);
    p = NULL;
    break;
  case MCLOSE + 0:
    p = "MATCH END";
    break;
  case MCLOSE + 1:
  case MCLOSE + 2:
  case MCLOSE + 3:
  case MCLOSE + 4:
  case MCLOSE + 5:
  case MCLOSE + 6:
  case MCLOSE + 7:
  case MCLOSE + 8:
  case MCLOSE + 9:
    sprintf(buf + STRLEN(buf), "MCLOSE%d", OP(op) - MCLOSE);
    p = NULL;
    break;
  case BACKREF + 1:
  case BACKREF + 2:
  case BACKREF + 3:
  case BACKREF + 4:
  case BACKREF + 5:
  case BACKREF + 6:
  case BACKREF + 7:
  case BACKREF + 8:
  case BACKREF + 9:
    sprintf(buf + STRLEN(buf), "BACKREF%d", OP(op) - BACKREF);
    p = NULL;
    break;
  case NOPEN:
    p = "NOPEN";
    break;
  case NCLOSE:
    p = "NCLOSE";
    break;
  case STAR:
    p = "STAR";
    break;
  case PLUS:
    p = "PLUS";
    break;
  case NOMATCH:
    p = "NOMATCH";
    break;
  case MATCH:
    p = "MATCH";
    break;
  case BEHIND:
    p = "BEHIND";
    break;
  case NOBEHIND:
    p = "NOBEHIND";
    break;
  case SUBPAT:
    p = "SUBPAT";
    break;
  case BRACE_LIMITS:
    p = "BRACE_LIMITS";
    break;
  case BRACE_SIMPLE:
    p = "BRACE_SIMPLE";
    break;
  case BRACE_COMPLEX + 0:
  case BRACE_COMPLEX + 1:
  case BRACE_COMPLEX + 2:
  case BRACE_COMPLEX + 3:
  case BRACE_COMPLEX + 4:
  case BRACE_COMPLEX + 5:
  case BRACE_COMPLEX + 6:
  case BRACE_COMPLEX + 7:
  case BRACE_COMPLEX + 8:
  case BRACE_COMPLEX + 9:
    sprintf(buf + STRLEN(buf), "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
    p = NULL;
    break;
  case MULTIBYTECODE:
    p = "MULTIBYTECODE";
    break;
  case NEWL:
    p = "NEWL";
    break;
  default:
    sprintf(buf + STRLEN(buf), "corrupt %d", OP(op));
    p = NULL;
    break;
  }
  if (p != NULL)
    STRCAT(buf, p);
  return (char_u *)buf;
}
#endif /* DEBUG */

/*
 * Used in a place where no * or \+ can follow.
 */
static int
re_mult_next(char *what)
{
  if (re_multi_type(peekchr()) == MULTI_MULT)
  {
    semsg(_("E888: (NFA regexp) cannot repeat %s"), what);
    rc_did_emsg = TRUE;
    return FAIL;
  }
  return OK;
}

typedef struct
{
  int a, b, c;
} decomp_T;

/* 0xfb20 - 0xfb4f */
static decomp_T decomp_table[0xfb4f - 0xfb20 + 1] =
    {
        {0x5e2, 0, 0},         /* 0xfb20	alt ayin */
        {0x5d0, 0, 0},         /* 0xfb21	alt alef */
        {0x5d3, 0, 0},         /* 0xfb22	alt dalet */
        {0x5d4, 0, 0},         /* 0xfb23	alt he */
        {0x5db, 0, 0},         /* 0xfb24	alt kaf */
        {0x5dc, 0, 0},         /* 0xfb25	alt lamed */
        {0x5dd, 0, 0},         /* 0xfb26	alt mem-sofit */
        {0x5e8, 0, 0},         /* 0xfb27	alt resh */
        {0x5ea, 0, 0},         /* 0xfb28	alt tav */
        {'+', 0, 0},           /* 0xfb29	alt plus */
        {0x5e9, 0x5c1, 0},     /* 0xfb2a	shin+shin-dot */
        {0x5e9, 0x5c2, 0},     /* 0xfb2b	shin+sin-dot */
        {0x5e9, 0x5c1, 0x5bc}, /* 0xfb2c	shin+shin-dot+dagesh */
        {0x5e9, 0x5c2, 0x5bc}, /* 0xfb2d	shin+sin-dot+dagesh */
        {0x5d0, 0x5b7, 0},     /* 0xfb2e	alef+patah */
        {0x5d0, 0x5b8, 0},     /* 0xfb2f	alef+qamats */
        {0x5d0, 0x5b4, 0},     /* 0xfb30	alef+hiriq */
        {0x5d1, 0x5bc, 0},     /* 0xfb31	bet+dagesh */
        {0x5d2, 0x5bc, 0},     /* 0xfb32	gimel+dagesh */
        {0x5d3, 0x5bc, 0},     /* 0xfb33	dalet+dagesh */
        {0x5d4, 0x5bc, 0},     /* 0xfb34	he+dagesh */
        {0x5d5, 0x5bc, 0},     /* 0xfb35	vav+dagesh */
        {0x5d6, 0x5bc, 0},     /* 0xfb36	zayin+dagesh */
        {0xfb37, 0, 0},        /* 0xfb37 -- UNUSED */
        {0x5d8, 0x5bc, 0},     /* 0xfb38	tet+dagesh */
        {0x5d9, 0x5bc, 0},     /* 0xfb39	yud+dagesh */
        {0x5da, 0x5bc, 0},     /* 0xfb3a	kaf sofit+dagesh */
        {0x5db, 0x5bc, 0},     /* 0xfb3b	kaf+dagesh */
        {0x5dc, 0x5bc, 0},     /* 0xfb3c	lamed+dagesh */
        {0xfb3d, 0, 0},        /* 0xfb3d -- UNUSED */
        {0x5de, 0x5bc, 0},     /* 0xfb3e	mem+dagesh */
        {0xfb3f, 0, 0},        /* 0xfb3f -- UNUSED */
        {0x5e0, 0x5bc, 0},     /* 0xfb40	nun+dagesh */
        {0x5e1, 0x5bc, 0},     /* 0xfb41	samech+dagesh */
        {0xfb42, 0, 0},        /* 0xfb42 -- UNUSED */
        {0x5e3, 0x5bc, 0},     /* 0xfb43	pe sofit+dagesh */
        {0x5e4, 0x5bc, 0},     /* 0xfb44	pe+dagesh */
        {0xfb45, 0, 0},        /* 0xfb45 -- UNUSED */
        {0x5e6, 0x5bc, 0},     /* 0xfb46	tsadi+dagesh */
        {0x5e7, 0x5bc, 0},     /* 0xfb47	qof+dagesh */
        {0x5e8, 0x5bc, 0},     /* 0xfb48	resh+dagesh */
        {0x5e9, 0x5bc, 0},     /* 0xfb49	shin+dagesh */
        {0x5ea, 0x5bc, 0},     /* 0xfb4a	tav+dagesh */
        {0x5d5, 0x5b9, 0},     /* 0xfb4b	vav+holam */
        {0x5d1, 0x5bf, 0},     /* 0xfb4c	bet+rafe */
        {0x5db, 0x5bf, 0},     /* 0xfb4d	kaf+rafe */
        {0x5e4, 0x5bf, 0},     /* 0xfb4e	pe+rafe */
        {0x5d0, 0x5dc, 0}      /* 0xfb4f	alef-lamed */
};

static void
mb_decompose(int c, int *c1, int *c2, int *c3)
{
  decomp_T d;

  if (c >= 0xfb20 && c <= 0xfb4f)
  {
    d = decomp_table[c - 0xfb20];
    *c1 = d.a;
    *c2 = d.b;
    *c3 = d.c;
  }
  else
  {
    *c1 = c;
    *c2 = *c3 = 0;
  }
}

/*
 * Compare two strings, ignore case if rex.reg_ic set.
 * Return 0 if strings match, non-zero otherwise.
 * Correct the length "*n" when composing characters are ignored.
 */
static int
cstrncmp(char_u *s1, char_u *s2, int *n)
{
  int result;

  if (!rex.reg_ic)
    result = STRNCMP(s1, s2, *n);
  else
    result = MB_STRNICMP(s1, s2, *n);

  /* if it failed and it's utf8 and we want to combineignore: */
  if (result != 0 && enc_utf8 && rex.reg_icombine)
  {
    char_u *str1, *str2;
    int c1, c2, c11, c12;
    int junk;

    /* we have to handle the strcmp ourselves, since it is necessary to
	 * deal with the composing characters by ignoring them: */
    str1 = s1;
    str2 = s2;
    c1 = c2 = 0;
    while ((int)(str1 - s1) < *n)
    {
      c1 = mb_ptr2char_adv(&str1);
      c2 = mb_ptr2char_adv(&str2);

      /* decompose the character if necessary, into 'base' characters
	     * because I don't care about Arabic, I will hard-code the Hebrew
	     * which I *do* care about!  So sue me... */
      if (c1 != c2 && (!rex.reg_ic || utf_fold(c1) != utf_fold(c2)))
      {
        /* decomposition necessary? */
        mb_decompose(c1, &c11, &junk, &junk);
        mb_decompose(c2, &c12, &junk, &junk);
        c1 = c11;
        c2 = c12;
        if (c11 != c12 && (!rex.reg_ic || utf_fold(c11) != utf_fold(c12)))
          break;
      }
    }
    result = c2 - c1;
    if (result == 0)
      *n = (int)(str2 - s2);
  }

  return result;
}

/*
 * cstrchr: This function is used a lot for simple searches, keep it fast!
 */
static char_u *
cstrchr(char_u *s, int c)
{
  char_u *p;
  int cc;

  if (!rex.reg_ic || (!enc_utf8 && mb_char2len(c) > 1))
    return vim_strchr(s, c);

  /* tolower() and toupper() can be slow, comparing twice should be a lot
     * faster (esp. when using MS Visual C++!).
     * For UTF-8 need to use folded case. */
  if (enc_utf8 && c > 0x80)
    cc = utf_fold(c);
  else if (MB_ISUPPER(c))
    cc = MB_TOLOWER(c);
  else if (MB_ISLOWER(c))
    cc = MB_TOUPPER(c);
  else
    return vim_strchr(s, c);

  if (has_mbyte)
  {
    for (p = s; *p != NUL; p += (*mb_ptr2len)(p))
    {
      if (enc_utf8 && c > 0x80)
      {
        if (utf_fold(utf_ptr2char(p)) == cc)
          return p;
      }
      else if (*p == c || *p == cc)
        return p;
    }
  }
  else
    /* Faster version for when there are no multi-byte characters. */
    for (p = s; *p != NUL; ++p)
      if (*p == c || *p == cc)
        return p;

  return NULL;
}

/***************************************************************
 *		      regsub stuff			       *
 ***************************************************************/

/*
 * We should define ftpr as a pointer to a function returning a pointer to
 * a function returning a pointer to a function ...
 * This is impossible, so we declare a pointer to a function returning a
 * pointer to a function returning void. This should work for all compilers.
 */
typedef void (*(*fptr_T)(int *, int))();

static int vim_regsub_both(char_u *source, typval_T *expr, char_u *dest, int copy, int magic, int backslash);

static fptr_T
do_upper(int *d, int c)
{
  *d = MB_TOUPPER(c);

  return (fptr_T)NULL;
}

static fptr_T
do_Upper(int *d, int c)
{
  *d = MB_TOUPPER(c);

  return (fptr_T)do_Upper;
}

static fptr_T
do_lower(int *d, int c)
{
  *d = MB_TOLOWER(c);

  return (fptr_T)NULL;
}

static fptr_T
do_Lower(int *d, int c)
{
  *d = MB_TOLOWER(c);

  return (fptr_T)do_Lower;
}

/*
 * regtilde(): Replace tildes in the pattern by the old pattern.
 *
 * Short explanation of the tilde: It stands for the previous replacement
 * pattern.  If that previous pattern also contains a ~ we should go back a
 * step further...  But we insert the previous pattern into the current one
 * and remember that.
 * This still does not handle the case where "magic" changes.  So require the
 * user to keep his hands off of "magic".
 *
 * The tildes are parsed once before the first call to vim_regsub().
 */
char_u *
regtilde(char_u *source, int magic)
{
  char_u *newsub = source;
  char_u *tmpsub;
  char_u *p;
  int len;
  int prevlen;

  for (p = newsub; *p; ++p)
  {
    if ((*p == '~' && magic) || (*p == '\\' && *(p + 1) == '~' && !magic))
    {
      if (reg_prev_sub != NULL)
      {
        /* length = len(newsub) - 1 + len(prev_sub) + 1 */
        prevlen = (int)STRLEN(reg_prev_sub);
        tmpsub = alloc(STRLEN(newsub) + prevlen);
        if (tmpsub != NULL)
        {
          /* copy prefix */
          len = (int)(p - newsub); /* not including ~ */
          mch_memmove(tmpsub, newsub, (size_t)len);
          /* interpret tilde */
          mch_memmove(tmpsub + len, reg_prev_sub, (size_t)prevlen);
          /* copy postfix */
          if (!magic)
            ++p; /* back off \ */
          STRCPY(tmpsub + len + prevlen, p + 1);

          if (newsub != source) /* already allocated newsub */
            vim_free(newsub);
          newsub = tmpsub;
          p = newsub + len + prevlen;
        }
      }
      else if (magic)
        STRMOVE(p, p + 1); /* remove '~' */
      else
        STRMOVE(p, p + 2); /* remove '\~' */
      --p;
    }
    else
    {
      if (*p == '\\' && p[1]) /* skip escaped characters */
        ++p;
      if (has_mbyte)
        p += (*mb_ptr2len)(p)-1;
    }
  }

  vim_free(reg_prev_sub);
  if (newsub != source) /* newsub was allocated, just keep it */
    reg_prev_sub = newsub;
  else /* no ~ found, need to save newsub  */
    reg_prev_sub = vim_strsave(newsub);
  return newsub;
}

#ifdef FEAT_EVAL
static int can_f_submatch = FALSE; /* TRUE when submatch() can be used */

/* These pointers are used for reg_submatch().  Needed for when the
 * substitution string is an expression that contains a call to substitute()
 * and submatch(). */
typedef struct
{
  regmatch_T *sm_match;
  regmmatch_T *sm_mmatch;
  linenr_T sm_firstlnum;
  linenr_T sm_maxline;
  int sm_line_lbr;
} regsubmatch_T;

static regsubmatch_T rsm; /* can only be used when can_f_submatch is TRUE */
#endif

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) || defined(PROTO)

/*
 * Put the submatches in "argv[0]" which is a list passed into call_func() by
 * vim_regsub_both().
 */
static int
fill_submatch_list(int argc UNUSED, typval_T *argv, int argcount)
{
  listitem_T *li;
  int i;
  char_u *s;

  if (argcount == 0)
    /* called function doesn't take an argument */
    return 0;

  /* Relies on sl_list to be the first item in staticList10_T. */
  init_static_list((staticList10_T *)(argv->vval.v_list));

  /* There are always 10 list items in staticList10_T. */
  li = argv->vval.v_list->lv_first;
  for (i = 0; i < 10; ++i)
  {
    s = rsm.sm_match->startp[i];
    if (s == NULL || rsm.sm_match->endp[i] == NULL)
      s = NULL;
    else
      s = vim_strnsave(s, (int)(rsm.sm_match->endp[i] - s));
    li->li_tv.v_type = VAR_STRING;
    li->li_tv.vval.v_string = s;
    li = li->li_next;
  }
  return 1;
}

static void
clear_submatch_list(staticList10_T *sl)
{
  int i;

  for (i = 0; i < 10; ++i)
    vim_free(sl->sl_items[i].li_tv.vval.v_string);
}

/*
 * vim_regsub() - perform substitutions after a vim_regexec() or
 * vim_regexec_multi() match.
 *
 * If "copy" is TRUE really copy into "dest".
 * If "copy" is FALSE nothing is copied, this is just to find out the length
 * of the result.
 *
 * If "backslash" is TRUE, a backslash will be removed later, need to double
 * them to keep them, and insert a backslash before a CR to avoid it being
 * replaced with a line break later.
 *
 * Note: The matched text must not change between the call of
 * vim_regexec()/vim_regexec_multi() and vim_regsub()!  It would make the back
 * references invalid!
 *
 * Returns the size of the replacement, including terminating NUL.
 */
int vim_regsub(
    regmatch_T *rmp,
    char_u *source,
    typval_T *expr,
    char_u *dest,
    int copy,
    int magic,
    int backslash)
{
  int result;
  regexec_T rex_save;
  int rex_in_use_save = rex_in_use;

  if (rex_in_use)
    /* Being called recursively, save the state. */
    rex_save = rex;
  rex_in_use = TRUE;

  rex.reg_match = rmp;
  rex.reg_mmatch = NULL;
  rex.reg_maxline = 0;
  rex.reg_buf = curbuf;
  rex.reg_line_lbr = TRUE;
  result = vim_regsub_both(source, expr, dest, copy, magic, backslash);

  rex_in_use = rex_in_use_save;
  if (rex_in_use)
    rex = rex_save;

  return result;
}
#endif

int vim_regsub_multi(
    regmmatch_T *rmp,
    linenr_T lnum,
    char_u *source,
    char_u *dest,
    int copy,
    int magic,
    int backslash)
{
  int result;
  regexec_T rex_save;
  int rex_in_use_save = rex_in_use;

  if (rex_in_use)
    /* Being called recursively, save the state. */
    rex_save = rex;
  rex_in_use = TRUE;

  rex.reg_match = NULL;
  rex.reg_mmatch = rmp;
  rex.reg_buf = curbuf; /* always works on the current buffer! */
  rex.reg_firstlnum = lnum;
  rex.reg_maxline = curbuf->b_ml.ml_line_count - lnum;
  rex.reg_line_lbr = FALSE;
  result = vim_regsub_both(source, NULL, dest, copy, magic, backslash);

  rex_in_use = rex_in_use_save;
  if (rex_in_use)
    rex = rex_save;

  return result;
}

static int
vim_regsub_both(
    char_u *source,
    typval_T *expr,
    char_u *dest,
    int copy,
    int magic,
    int backslash)
{
  char_u *src;
  char_u *dst;
  char_u *s;
  int c;
  int cc;
  int no = -1;
  fptr_T func_all = (fptr_T)NULL;
  fptr_T func_one = (fptr_T)NULL;
  linenr_T clnum = 0; /* init for GCC */
  int len = 0;        /* init for GCC */
#ifdef FEAT_EVAL
  static char_u *eval_result = NULL;
#endif

  /* Be paranoid... */
  if ((source == NULL && expr == NULL) || dest == NULL)
  {
    emsg(_(e_null));
    return 0;
  }
  if (prog_magic_wrong())
    return 0;
  src = source;
  dst = dest;

  /*
     * When the substitute part starts with "\=" evaluate it as an expression.
     */
  if (expr != NULL || (source[0] == '\\' && source[1] == '='))
  {
#ifdef FEAT_EVAL
    /* To make sure that the length doesn't change between checking the
	 * length and copying the string, and to speed up things, the
	 * resulting string is saved from the call with "copy" == FALSE to the
	 * call with "copy" == TRUE. */
    if (copy)
    {
      if (eval_result != NULL)
      {
        STRCPY(dest, eval_result);
        dst += STRLEN(eval_result);
        VIM_CLEAR(eval_result);
      }
    }
    else
    {
      int prev_can_f_submatch = can_f_submatch;
      regsubmatch_T rsm_save;

      vim_free(eval_result);

      /* The expression may contain substitute(), which calls us
	     * recursively.  Make sure submatch() gets the text from the first
	     * level. */
      if (can_f_submatch)
        rsm_save = rsm;
      can_f_submatch = TRUE;
      rsm.sm_match = rex.reg_match;
      rsm.sm_mmatch = rex.reg_mmatch;
      rsm.sm_firstlnum = rex.reg_firstlnum;
      rsm.sm_maxline = rex.reg_maxline;
      rsm.sm_line_lbr = rex.reg_line_lbr;

      if (expr != NULL)
      {
        typval_T argv[2];
        int dummy;
        char_u buf[NUMBUFLEN];
        typval_T rettv;
        staticList10_T matchList;

        rettv.v_type = VAR_STRING;
        rettv.vval.v_string = NULL;
        argv[0].v_type = VAR_LIST;
        argv[0].vval.v_list = &matchList.sl_list;
        matchList.sl_list.lv_len = 0;
        if (expr->v_type == VAR_FUNC)
        {
          s = expr->vval.v_string;
          call_func(s, -1, &rettv,
                    1, argv, fill_submatch_list,
                    0L, 0L, &dummy, TRUE, NULL, NULL);
        }
        else if (expr->v_type == VAR_PARTIAL)
        {
          partial_T *partial = expr->vval.v_partial;

          s = partial_name(partial);
          call_func(s, -1, &rettv,
                    1, argv, fill_submatch_list,
                    0L, 0L, &dummy, TRUE, partial, NULL);
        }
        if (matchList.sl_list.lv_len > 0)
          /* fill_submatch_list() was called */
          clear_submatch_list(&matchList);

        eval_result = tv_get_string_buf_chk(&rettv, buf);
        if (eval_result != NULL)
          eval_result = vim_strsave(eval_result);
        clear_tv(&rettv);
      }
      else
        eval_result = eval_to_string(source + 2, NULL, TRUE);

      if (eval_result != NULL)
      {
        int had_backslash = FALSE;

        for (s = eval_result; *s != NUL; MB_PTR_ADV(s))
        {
          /* Change NL to CR, so that it becomes a line break,
		     * unless called from vim_regexec_nl().
		     * Skip over a backslashed character. */
          if (*s == NL && !rsm.sm_line_lbr)
            *s = CAR;
          else if (*s == '\\' && s[1] != NUL)
          {
            ++s;
            /* Change NL to CR here too, so that this works:
			 * :s/abc\\\ndef/\="aaa\\\nbbb"/  on text:
			 *   abc\
			 *   def
			 * Not when called from vim_regexec_nl().
			 */
            if (*s == NL && !rsm.sm_line_lbr)
              *s = CAR;
            had_backslash = TRUE;
          }
        }
        if (had_backslash && backslash)
        {
          /* Backslashes will be consumed, need to double them. */
          s = vim_strsave_escaped(eval_result, (char_u *)"\\");
          if (s != NULL)
          {
            vim_free(eval_result);
            eval_result = s;
          }
        }

        dst += STRLEN(eval_result);
      }

      can_f_submatch = prev_can_f_submatch;
      if (can_f_submatch)
        rsm = rsm_save;
    }
#endif
  }
  else
    while ((c = *src++) != NUL)
    {
      if (c == '&' && magic)
        no = 0;
      else if (c == '\\' && *src != NUL)
      {
        if (*src == '&' && !magic)
        {
          ++src;
          no = 0;
        }
        else if ('0' <= *src && *src <= '9')
        {
          no = *src++ - '0';
        }
        else if (vim_strchr((char_u *)"uUlLeE", *src))
        {
          switch (*src++)
          {
          case 'u':
            func_one = (fptr_T)do_upper;
            continue;
          case 'U':
            func_all = (fptr_T)do_Upper;
            continue;
          case 'l':
            func_one = (fptr_T)do_lower;
            continue;
          case 'L':
            func_all = (fptr_T)do_Lower;
            continue;
          case 'e':
          case 'E':
            func_one = func_all = (fptr_T)NULL;
            continue;
          }
        }
      }
      if (no < 0) /* Ordinary character. */
      {
        if (c == K_SPECIAL && src[0] != NUL && src[1] != NUL)
        {
          /* Copy a special key as-is. */
          if (copy)
          {
            *dst++ = c;
            *dst++ = *src++;
            *dst++ = *src++;
          }
          else
          {
            dst += 3;
            src += 2;
          }
          continue;
        }

        if (c == '\\' && *src != NUL)
        {
          /* Check for abbreviations -- webb */
          switch (*src)
          {
          case 'r':
            c = CAR;
            ++src;
            break;
          case 'n':
            c = NL;
            ++src;
            break;
          case 't':
            c = TAB;
            ++src;
            break;
            /* Oh no!  \e already has meaning in subst pat :-( */
            /* case 'e':   c = ESC;	++src;	break; */
          case 'b':
            c = Ctrl_H;
            ++src;
            break;

          /* If "backslash" is TRUE the backslash will be removed
		     * later.  Used to insert a literal CR. */
          default:
            if (backslash)
            {
              if (copy)
                *dst = '\\';
              ++dst;
            }
            c = *src++;
          }
        }
        else if (has_mbyte)
          c = mb_ptr2char(src - 1);

        /* Write to buffer, if copy is set. */
        if (func_one != (fptr_T)NULL)
          /* Turbo C complains without the typecast */
          func_one = (fptr_T)(func_one(&cc, c));
        else if (func_all != (fptr_T)NULL)
          /* Turbo C complains without the typecast */
          func_all = (fptr_T)(func_all(&cc, c));
        else /* just copy */
          cc = c;

        if (has_mbyte)
        {
          int totlen = mb_ptr2len(src - 1);

          if (copy)
            mb_char2bytes(cc, dst);
          dst += mb_char2len(cc) - 1;
          if (enc_utf8)
          {
            int clen = utf_ptr2len(src - 1);

            /* If the character length is shorter than "totlen", there
		     * are composing characters; copy them as-is. */
            if (clen < totlen)
            {
              if (copy)
                mch_memmove(dst + 1, src - 1 + clen,
                            (size_t)(totlen - clen));
              dst += totlen - clen;
            }
          }
          src += totlen - 1;
        }
        else if (copy)
          *dst = cc;
        dst++;
      }
      else
      {
        if (REG_MULTI)
        {
          clnum = rex.reg_mmatch->startpos[no].lnum;
          if (clnum < 0 || rex.reg_mmatch->endpos[no].lnum < 0)
            s = NULL;
          else
          {
            s = reg_getline(clnum) + rex.reg_mmatch->startpos[no].col;
            if (rex.reg_mmatch->endpos[no].lnum == clnum)
              len = rex.reg_mmatch->endpos[no].col - rex.reg_mmatch->startpos[no].col;
            else
              len = (int)STRLEN(s);
          }
        }
        else
        {
          s = rex.reg_match->startp[no];
          if (rex.reg_match->endp[no] == NULL)
            s = NULL;
          else
            len = (int)(rex.reg_match->endp[no] - s);
        }
        if (s != NULL)
        {
          for (;;)
          {
            if (len == 0)
            {
              if (REG_MULTI)
              {
                if (rex.reg_mmatch->endpos[no].lnum == clnum)
                  break;
                if (copy)
                  *dst = CAR;
                ++dst;
                s = reg_getline(++clnum);
                if (rex.reg_mmatch->endpos[no].lnum == clnum)
                  len = rex.reg_mmatch->endpos[no].col;
                else
                  len = (int)STRLEN(s);
              }
              else
                break;
            }
            else if (*s == NUL) /* we hit NUL. */
            {
              if (copy)
                emsg(_(e_re_damg));
              goto exit;
            }
            else
            {
              if (backslash && (*s == CAR || *s == '\\'))
              {
                /*
			     * Insert a backslash in front of a CR, otherwise
			     * it will be replaced by a line break.
			     * Number of backslashes will be halved later,
			     * double them here.
			     */
                if (copy)
                {
                  dst[0] = '\\';
                  dst[1] = *s;
                }
                dst += 2;
              }
              else
              {
                if (has_mbyte)
                  c = mb_ptr2char(s);
                else
                  c = *s;

                if (func_one != (fptr_T)NULL)
                  /* Turbo C complains without the typecast */
                  func_one = (fptr_T)(func_one(&cc, c));
                else if (func_all != (fptr_T)NULL)
                  /* Turbo C complains without the typecast */
                  func_all = (fptr_T)(func_all(&cc, c));
                else /* just copy */
                  cc = c;

                if (has_mbyte)
                {
                  int l;

                  /* Copy composing characters separately, one
				 * at a time. */
                  if (enc_utf8)
                    l = utf_ptr2len(s) - 1;
                  else
                    l = mb_ptr2len(s) - 1;

                  s += l;
                  len -= l;
                  if (copy)
                    mb_char2bytes(cc, dst);
                  dst += mb_char2len(cc) - 1;
                }
                else if (copy)
                  *dst = cc;
                dst++;
              }

              ++s;
              --len;
            }
          }
        }
        no = -1;
      }
    }
  if (copy)
    *dst = NUL;

exit:
  return (int)((dst - dest) + 1);
}

#ifdef FEAT_EVAL
/*
 * Call reg_getline() with the line numbers from the submatch.  If a
 * substitute() was used the reg_maxline and other values have been
 * overwritten.
 */
static char_u *
reg_getline_submatch(linenr_T lnum)
{
  char_u *s;
  linenr_T save_first = rex.reg_firstlnum;
  linenr_T save_max = rex.reg_maxline;

  rex.reg_firstlnum = rsm.sm_firstlnum;
  rex.reg_maxline = rsm.sm_maxline;

  s = reg_getline(lnum);

  rex.reg_firstlnum = save_first;
  rex.reg_maxline = save_max;
  return s;
}

/*
 * Used for the submatch() function: get the string from the n'th submatch in
 * allocated memory.
 * Returns NULL when not in a ":s" command and for a non-existing submatch.
 */
char_u *
reg_submatch(int no)
{
  char_u *retval = NULL;
  char_u *s;
  int len;
  int round;
  linenr_T lnum;

  if (!can_f_submatch || no < 0)
    return NULL;

  if (rsm.sm_match == NULL)
  {
    /*
	 * First round: compute the length and allocate memory.
	 * Second round: copy the text.
	 */
    for (round = 1; round <= 2; ++round)
    {
      lnum = rsm.sm_mmatch->startpos[no].lnum;
      if (lnum < 0 || rsm.sm_mmatch->endpos[no].lnum < 0)
        return NULL;

      s = reg_getline_submatch(lnum);
      if (s == NULL) // anti-crash check, cannot happen?
        break;
      s += rsm.sm_mmatch->startpos[no].col;
      if (rsm.sm_mmatch->endpos[no].lnum == lnum)
      {
        /* Within one line: take form start to end col. */
        len = rsm.sm_mmatch->endpos[no].col - rsm.sm_mmatch->startpos[no].col;
        if (round == 2)
          vim_strncpy(retval, s, len);
        ++len;
      }
      else
      {
        /* Multiple lines: take start line from start col, middle
		 * lines completely and end line up to end col. */
        len = (int)STRLEN(s);
        if (round == 2)
        {
          STRCPY(retval, s);
          retval[len] = '\n';
        }
        ++len;
        ++lnum;
        while (lnum < rsm.sm_mmatch->endpos[no].lnum)
        {
          s = reg_getline_submatch(lnum++);
          if (round == 2)
            STRCPY(retval + len, s);
          len += (int)STRLEN(s);
          if (round == 2)
            retval[len] = '\n';
          ++len;
        }
        if (round == 2)
          STRNCPY(retval + len, reg_getline_submatch(lnum),
                  rsm.sm_mmatch->endpos[no].col);
        len += rsm.sm_mmatch->endpos[no].col;
        if (round == 2)
          retval[len] = NUL;
        ++len;
      }

      if (retval == NULL)
      {
        retval = alloc(len);
        if (retval == NULL)
          return NULL;
      }
    }
  }
  else
  {
    s = rsm.sm_match->startp[no];
    if (s == NULL || rsm.sm_match->endp[no] == NULL)
      retval = NULL;
    else
      retval = vim_strnsave(s, (int)(rsm.sm_match->endp[no] - s));
  }

  return retval;
}

/*
 * Used for the submatch() function with the optional non-zero argument: get
 * the list of strings from the n'th submatch in allocated memory with NULs
 * represented in NLs.
 * Returns a list of allocated strings.  Returns NULL when not in a ":s"
 * command, for a non-existing submatch and for any error.
 */
list_T *
reg_submatch_list(int no)
{
  char_u *s;
  linenr_T slnum;
  linenr_T elnum;
  colnr_T scol;
  colnr_T ecol;
  int i;
  list_T *list;
  int error = FALSE;

  if (!can_f_submatch || no < 0)
    return NULL;

  if (rsm.sm_match == NULL)
  {
    slnum = rsm.sm_mmatch->startpos[no].lnum;
    elnum = rsm.sm_mmatch->endpos[no].lnum;
    if (slnum < 0 || elnum < 0)
      return NULL;

    scol = rsm.sm_mmatch->startpos[no].col;
    ecol = rsm.sm_mmatch->endpos[no].col;

    list = list_alloc();
    if (list == NULL)
      return NULL;

    s = reg_getline_submatch(slnum) + scol;
    if (slnum == elnum)
    {
      if (list_append_string(list, s, ecol - scol) == FAIL)
        error = TRUE;
    }
    else
    {
      if (list_append_string(list, s, -1) == FAIL)
        error = TRUE;
      for (i = 1; i < elnum - slnum; i++)
      {
        s = reg_getline_submatch(slnum + i);
        if (list_append_string(list, s, -1) == FAIL)
          error = TRUE;
      }
      s = reg_getline_submatch(elnum);
      if (list_append_string(list, s, ecol) == FAIL)
        error = TRUE;
    }
  }
  else
  {
    s = rsm.sm_match->startp[no];
    if (s == NULL || rsm.sm_match->endp[no] == NULL)
      return NULL;
    list = list_alloc();
    if (list == NULL)
      return NULL;
    if (list_append_string(list, s,
                           (int)(rsm.sm_match->endp[no] - s)) == FAIL)
      error = TRUE;
  }

  if (error)
  {
    list_free(list);
    return NULL;
  }
  return list;
}
#endif

static regengine_T bt_regengine =
    {
        bt_regcomp,
        bt_regfree,
        bt_regexec_nl,
        bt_regexec_multi,
        (char_u *)""};

#include "regexp_nfa.c"

static regengine_T nfa_regengine =
    {
        nfa_regcomp,
        nfa_regfree,
        nfa_regexec_nl,
        nfa_regexec_multi,
        (char_u *)""};

/* Which regexp engine to use? Needed for vim_regcomp().
 * Must match with 'regexpengine'. */
static int regexp_engine = 0;

#ifdef DEBUG
static char_u regname[][30] = {
    "AUTOMATIC Regexp Engine",
    "BACKTRACKING Regexp Engine",
    "NFA Regexp Engine"};
#endif

/*
 * Compile a regular expression into internal code.
 * Returns the program in allocated memory.
 * Use vim_regfree() to free the memory.
 * Returns NULL for an error.
 */
regprog_T *
vim_regcomp(char_u *expr_arg, int re_flags)
{
  regprog_T *prog = NULL;
  char_u *expr = expr_arg;
  int save_called_emsg;

  regexp_engine = p_re;

  /* Check for prefix "\%#=", that sets the regexp engine */
  if (STRNCMP(expr, "\\%#=", 4) == 0)
  {
    int newengine = expr[4] - '0';

    if (newengine == AUTOMATIC_ENGINE || newengine == BACKTRACKING_ENGINE || newengine == NFA_ENGINE)
    {
      regexp_engine = expr[4] - '0';
      expr += 5;
#ifdef DEBUG
      smsg("New regexp mode selected (%d): %s",
           regexp_engine, regname[newengine]);
#endif
    }
    else
    {
      emsg(_("E864: \\%#= can only be followed by 0, 1, or 2. The automatic engine will be used "));
      regexp_engine = AUTOMATIC_ENGINE;
    }
  }
#ifdef DEBUG
  bt_regengine.expr = expr;
  nfa_regengine.expr = expr;
#endif
  // reg_iswordc() uses rex.reg_buf
  rex.reg_buf = curbuf;

  /*
     * First try the NFA engine, unless backtracking was requested.
     */
  save_called_emsg = called_emsg;
  called_emsg = FALSE;
  if (regexp_engine != BACKTRACKING_ENGINE)
    prog = nfa_regengine.regcomp(expr,
                                 re_flags + (regexp_engine == AUTOMATIC_ENGINE ? RE_AUTO : 0));
  else
    prog = bt_regengine.regcomp(expr, re_flags);

  /* Check for error compiling regexp with initial engine. */
  if (prog == NULL)
  {
#ifdef BT_REGEXP_DEBUG_LOG
    if (regexp_engine != BACKTRACKING_ENGINE) /* debugging log for NFA */
    {
      FILE *f;
      f = fopen(BT_REGEXP_DEBUG_LOG_NAME, "a");
      if (f)
      {
        fprintf(f, "Syntax error in \"%s\"\n", expr);
        fclose(f);
      }
      else
        semsg("(NFA) Could not open \"%s\" to write !!!",
              BT_REGEXP_DEBUG_LOG_NAME);
    }
#endif
    /*
	 * If the NFA engine failed, try the backtracking engine.
	 * The NFA engine also fails for patterns that it can't handle well
	 * but are still valid patterns, thus a retry should work.
	 * But don't try if an error message was given.
	 */
    if (regexp_engine == AUTOMATIC_ENGINE && !called_emsg)
    {
      regexp_engine = BACKTRACKING_ENGINE;
      prog = bt_regengine.regcomp(expr, re_flags);
    }
  }
  called_emsg |= save_called_emsg;

  if (prog != NULL)
  {
    /* Store the info needed to call regcomp() again when the engine turns
	 * out to be very slow when executing it. */
    prog->re_engine = regexp_engine;
    prog->re_flags = re_flags;
  }

  return prog;
}

/*
 * Free a compiled regexp program, returned by vim_regcomp().
 */
void vim_regfree(regprog_T *prog)
{
  if (prog != NULL)
    prog->engine->regfree(prog);
}

#ifdef FEAT_EVAL
static void
report_re_switch(char_u *pat)
{
  if (p_verbose > 0)
  {
    verbose_enter();
    msg_puts(_("Switching to backtracking RE engine for pattern: "));
    msg_puts((char *)pat);
    verbose_leave();
  }
}
#endif

#if defined(FEAT_XCLIPBOARD)
/*
 * Return whether "prog" is currently being executed.
 */
int regprog_in_use(regprog_T *prog)
{
  return prog->re_in_use;
}
#endif

/*
 * Match a regexp against a string.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Note: "rmp->regprog" may be freed and changed.
 * Uses curbuf for line count and 'iskeyword'.
 * When "nl" is TRUE consider a "\n" in "line" to be a line break.
 *
 * Return TRUE if there is a match, FALSE if not.
 */
static int
vim_regexec_string(
    regmatch_T *rmp,
    char_u *line, /* string to match against */
    colnr_T col,  /* column to start looking for match */
    int nl)
{
  int result;
  regexec_T rex_save;
  int rex_in_use_save = rex_in_use;

  // Cannot use the same prog recursively, it contains state.
  if (rmp->regprog->re_in_use)
  {
    emsg(_(e_recursive));
    return FALSE;
  }
  rmp->regprog->re_in_use = TRUE;

  if (rex_in_use)
    // Being called recursively, save the state.
    rex_save = rex;
  rex_in_use = TRUE;

  rex.reg_startp = NULL;
  rex.reg_endp = NULL;
  rex.reg_startpos = NULL;
  rex.reg_endpos = NULL;

  result = rmp->regprog->engine->regexec_nl(rmp, line, col, nl);
  rmp->regprog->re_in_use = FALSE;

  /* NFA engine aborted because it's very slow. */
  if (rmp->regprog->re_engine == AUTOMATIC_ENGINE && result == NFA_TOO_EXPENSIVE)
  {
    int save_p_re = p_re;
    int re_flags = rmp->regprog->re_flags;
    char_u *pat = vim_strsave(((nfa_regprog_T *)rmp->regprog)->pattern);

    p_re = BACKTRACKING_ENGINE;
    vim_regfree(rmp->regprog);
    if (pat != NULL)
    {
#ifdef FEAT_EVAL
      report_re_switch(pat);
#endif
      rmp->regprog = vim_regcomp(pat, re_flags);
      if (rmp->regprog != NULL)
      {
        rmp->regprog->re_in_use = TRUE;
        result = rmp->regprog->engine->regexec_nl(rmp, line, col, nl);
        rmp->regprog->re_in_use = FALSE;
      }
      vim_free(pat);
    }

    p_re = save_p_re;
  }

  rex_in_use = rex_in_use_save;
  if (rex_in_use)
    rex = rex_save;

  return result > 0;
}

/*
 * Note: "*prog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
int vim_regexec_prog(
    regprog_T **prog,
    int ignore_case,
    char_u *line,
    colnr_T col)
{
  int r;
  regmatch_T regmatch;

  regmatch.regprog = *prog;
  regmatch.rm_ic = ignore_case;
  r = vim_regexec_string(&regmatch, line, col, FALSE);
  *prog = regmatch.regprog;
  return r;
}

/*
 * Note: "rmp->regprog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
int vim_regexec(regmatch_T *rmp, char_u *line, colnr_T col)
{
  return vim_regexec_string(rmp, line, col, FALSE);
}

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) || defined(FIND_REPLACE_DIALOG) || defined(PROTO)
/*
 * Like vim_regexec(), but consider a "\n" in "line" to be a line break.
 * Note: "rmp->regprog" may be freed and changed.
 * Return TRUE if there is a match, FALSE if not.
 */
int vim_regexec_nl(regmatch_T *rmp, char_u *line, colnr_T col)
{
  return vim_regexec_string(rmp, line, col, TRUE);
}
#endif

/*
 * Match a regexp against multiple lines.
 * "rmp->regprog" must be a compiled regexp as returned by vim_regcomp().
 * Note: "rmp->regprog" may be freed and changed, even set to NULL.
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return zero if there is no match.  Return number of lines contained in the
 * match otherwise.
 */
long vim_regexec_multi(
    regmmatch_T *rmp,
    win_T *win,     /* window in which to search or NULL */
    buf_T *buf,     /* buffer in which to search */
    linenr_T lnum,  /* nr of line to start looking for match */
    colnr_T col,    /* column to start looking for match */
    proftime_T *tm, /* timeout limit or NULL */
    int *timed_out) /* flag is set when timeout limit reached */
{
  int result;
  regexec_T rex_save;
  int rex_in_use_save = rex_in_use;

  // Cannot use the same prog recursively, it contains state.
  if (rmp->regprog->re_in_use)
  {
    emsg(_(e_recursive));
    return FALSE;
  }
  rmp->regprog->re_in_use = TRUE;

  if (rex_in_use)
    /* Being called recursively, save the state. */
    rex_save = rex;
  rex_in_use = TRUE;

  result = rmp->regprog->engine->regexec_multi(
      rmp, win, buf, lnum, col, tm, timed_out);
  rmp->regprog->re_in_use = FALSE;

  /* NFA engine aborted because it's very slow. */
  if (rmp->regprog->re_engine == AUTOMATIC_ENGINE && result == NFA_TOO_EXPENSIVE)
  {
    int save_p_re = p_re;
    int re_flags = rmp->regprog->re_flags;
    char_u *pat = vim_strsave(((nfa_regprog_T *)rmp->regprog)->pattern);

    p_re = BACKTRACKING_ENGINE;
    vim_regfree(rmp->regprog);
    if (pat != NULL)
    {
#ifdef FEAT_EVAL
      report_re_switch(pat);
#endif
      rmp->regprog = vim_regcomp(pat, re_flags);

      if (rmp->regprog != NULL)
      {
        rmp->regprog->re_in_use = TRUE;
        result = rmp->regprog->engine->regexec_multi(
            rmp, win, buf, lnum, col, tm, timed_out);
        rmp->regprog->re_in_use = FALSE;
      }
      vim_free(pat);
    }
    p_re = save_p_re;
  }

  rex_in_use = rex_in_use_save;
  if (rex_in_use)
    rex = rex_save;

  return result <= 0 ? 0 : result;
}
