/*	$NetBSD: getcwd.c,v 1.53 2012/06/21 23:29:23 enami Exp $	*/

/*
 * Copyright (c) 1989, 1991, 1993, 1995
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/stat.h>

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "extern.h"

/*
 * char *realpath(const char *path, char *resolved);
 *
 * Find the real name of path, by removing all ".", ".." and symlink
 * components.  Returns (resolved) on success, or (NULL) on failure,
 * in which case the path which caused trouble is left in (resolved).
 */
char *realpath(const char *__restrict path, char *__restrict resolved) {
  struct stat sb;
  int idx = 0, nlnk = 0;
  const char *q;
  char *p, wbuf[2][MAXPATHLEN], *fres;
  size_t len;
  ssize_t n;

  /* POSIX sez we must test for this */
  if (path == NULL) {
    errno = EINVAL;
    return NULL;
  }

  if (resolved == NULL) {
    fres = resolved = malloc(MAXPATHLEN);
    if (resolved == NULL)
      return NULL;
  } else
    fres = NULL;

  /*
   * Build real path one by one with paying an attention to .,
   * .. and symbolic link.
   */

  /*
   * `p' is where we'll put a new component with prepending
   * a delimiter.
   */
  p = resolved;

  if (*path == '\0') {
    *p = '\0';
    errno = ENOENT;
    goto out;
  }

  /* If relative path, start from current working directory. */
  if (*path != '/') {
    /* check for resolved pointer to appease coverity */
    if (resolved && getcwd(resolved, MAXPATHLEN) == NULL) {
      p[0] = '.';
      p[1] = '\0';
      goto out;
    }
    len = strlen(resolved);
    if (len > 1)
      p += len;
  }

loop:
  /* Skip any slash. */
  while (*path == '/')
    path++;

  if (*path == '\0') {
    if (p == resolved)
      *p++ = '/';
    *p = '\0';
    return resolved;
  }

  /* Find the end of this component. */
  q = path;
  do
    q++;
  while (*q != '/' && *q != '\0');

  /* Test . or .. */
  if (path[0] == '.') {
    if (q - path == 1) {
      path = q;
      goto loop;
    }
    if (path[1] == '.' && q - path == 2) {
      /* Trim the last component. */
      if (p != resolved)
        while (*--p != '/')
          continue;
      path = q;
      goto loop;
    }
  }

  /* Append this component. */
  if (p - resolved + 1 + q - path + 1 > MAXPATHLEN) {
    errno = ENAMETOOLONG;
    if (p == resolved)
      *p++ = '/';
    *p = '\0';
    goto out;
  }
  p[0] = '/';
  memcpy(&p[1], path,
         /* LINTED We know q > path. */
         q - path);
  p[1 + q - path] = '\0';

  /*
   * If this component is a symlink, toss it and prepend link
   * target to unresolved path.
   */
  if (lstat(resolved, &sb) == -1)
    goto out;

  if (S_ISLNK(sb.st_mode)) {
    if (nlnk++ >= MAXSYMLINKS) {
      errno = ELOOP;
      goto out;
    }
    n = readlink(resolved, wbuf[idx], sizeof(wbuf[0]) - 1);
    if (n < 0)
      goto out;
    if (n == 0) {
      errno = ENOENT;
      goto out;
    }

    /* Append unresolved path to link target and switch to it. */
    if (n + (len = strlen(q)) + 1 > sizeof(wbuf[0])) {
      errno = ENAMETOOLONG;
      goto out;
    }
    memcpy(&wbuf[idx][n], q, len + 1);
    path = wbuf[idx];
    idx ^= 1;

    /* If absolute symlink, start from root. */
    if (*path == '/')
      p = resolved;
    goto loop;
  }
  if (*q == '/' && !S_ISDIR(sb.st_mode)) {
    errno = ENOTDIR;
    goto out;
  }

  /* Advance both resolved and unresolved path. */
  p += 1 + q - path;
  path = q;
  goto loop;
out:
  free(fres);
  return NULL;
}

char *getcwd(char *pt, size_t size) {
  char *npt;

  /*
   * If a buffer is specified, the size has to be non-zero.
   */
  if (pt != NULL) {
    if (size == 0) {
      /* __getcwd(pt, 0) results ERANGE. */
      errno = EINVAL;
      return (NULL);
    }
    if (__getcwd(pt, size) >= 0)
      return (pt);
    return (NULL);
  }

  /*
   * If no buffer specified by the user, allocate one as necessary.
   */
  size = 1024 >> 1;
  do {
    if ((npt = realloc(pt, size <<= 1)) == NULL)
      break;
    pt = npt;
    if (__getcwd(pt, size) >= 0)
      return (pt);
  } while (size <= MAXPATHLEN * 4 && errno == ERANGE);

  free(pt);
  return (NULL);
}
