/*	$NetBSD: refill.c,v 1.16 2012/03/27 15:05:42 christos Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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 <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include "reentrant.h"
#include "local.h"

#ifdef _REENTRANT
extern rwlock_t __sfp_lock;
#endif

static int lflush(FILE *fp) {

  _DIAGASSERT(fp != NULL);

  if ((fp->_flags & (__SLBF | __SWR)) == (__SLBF | __SWR))
    return __sflush(fp);
  return 0;
}

/*
 * Refill a stdio buffer.
 * Return EOF on eof or error, 0 otherwise.
 */
int __srefill(FILE *fp) {

  _DIAGASSERT(fp != NULL);

  /* make sure stdio is set up */
  if (!__sdidinit)
    __sinit();

  fp->_r = 0; /* largely a convenience for callers */

  /* SysV does not make this test; take it out for compatibility */
  if (fp->_flags & __SEOF)
    return EOF;

  /* if not already reading, have to be reading and writing */
  if ((fp->_flags & __SRD) == 0) {
    if ((fp->_flags & __SRW) == 0) {
      errno = EBADF;
      fp->_flags |= __SERR;
      return EOF;
    }
    /* switch to reading */
    if (fp->_flags & __SWR) {
      if (__sflush(fp))
        return EOF;
      fp->_flags &= ~__SWR;
      fp->_w = 0;
      fp->_lbfsize = 0;
    }
    fp->_flags |= __SRD;
  } else {
    /*
     * We were reading.  If there is an ungetc buffer,
     * we must have been reading from that.  Drop it,
     * restoring the previous buffer (if any).  If there
     * is anything in that buffer, return.
     */
    if (HASUB(fp)) {
      FREEUB(fp);
      if ((fp->_r = fp->_ur) != 0) {
        fp->_p = fp->_up;
        return 0;
      }
    }
  }

  if (fp->_bf._base == NULL)
    __smakebuf(fp);

  /*
   * Before reading from a line buffered or unbuffered file,
   * flush all line buffered output files, per the ANSI C
   * standard.
   */
  if (fp->_flags & (__SLBF | __SNBF)) {
    rwlock_rdlock(&__sfp_lock);
    (void)_fwalk(lflush);
    rwlock_unlock(&__sfp_lock);
  }
  fp->_p = fp->_bf._base;
  fp->_r =
    (int)(*fp->_read)(fp->_cookie, (char *)fp->_p, (size_t)fp->_bf._size);
  fp->_flags &= ~__SMOD; /* buffer contents are again pristine */
  if (fp->_r <= 0) {
    if (fp->_r == 0)
      fp->_flags |= __SEOF;
    else {
      fp->_r = 0;
      fp->_flags |= __SERR;
    }
    return EOF;
  }
  return 0;
}
