stdio/FreeBSD/fflush.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)fflush.c    8.1 (Berkeley) 6/4/93";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/fflush.c,v 1.13 2004/07/04 20:17:00 cperciva Exp $");
  42
  43 #include "namespace.h"
  44 #include <errno.h>
  45 #include <stdio.h>
  46 #include "un-namespace.h"
  47 #include "libc_private.h"
  48 #include "local.h"
  49
  50 static int      sflush_locked(FILE *);
  51
  52 /*
  53  * Flush a single file, or (if fp is NULL) all files.
  54  * MT-safe version
  55  */
  56 int
  57 fflush(FILE *fp)
  58 {
  59         int retval;
  60
  61         if (fp == NULL)
  62                 return (_fwalk(sflush_locked));
  63         FLOCKFILE(fp);
  64
  65         /*
  66          * There is disagreement about the correct behaviour of fflush()
  67          * when passed a file which is not open for reading.  According to
  68          * the ISO C standard, the behaviour is undefined.
  69          * Under linux, such an fflush returns success and has no effect;
  70          * under Windows, such an fflush is documented as behaving instead
  71          * as fpurge().
  72          * Given that applications may be written with the expectation of
  73          * either of these two behaviours, the only safe (non-astonishing)
  74          * option is to return EBADF and ask that applications be fixed.
  75          */
  76         if ((fp->_flags & (__SWR | __SRW)) == 0) {
  77                 errno = EBADF;
  78                 retval = EOF;
  79         } else
  80                 retval = __sflush(fp);
  81         FUNLOCKFILE(fp);
  82         return (retval);
  83 }
  84
  85 /*
  86  * Flush a single file, or (if fp is NULL) all files.
  87  * Non-MT-safe version
  88  */
  89 int
  90 __fflush(FILE *fp)
  91 {
  92         int retval;
  93
  94         if (fp == NULL)
  95                 return (_fwalk(sflush_locked));
  96         if ((fp->_flags & (__SWR | __SRW)) == 0) {
  97                 errno = EBADF;
  98                 retval = EOF;
  99         } else
 100                 retval = __sflush(fp);
 101         return (retval);
 102 }
 103
 104 int
 105 __sflush(FILE *fp)
 106 {
 107         unsigned char *p;
 108         int n, t;
 109
 110         t = fp->_flags;
 111         if ((t & __SWR) == 0)
 112                 return (0);
 113
 114         if ((p = fp->_bf._base) == NULL)
 115                 return (0);
 116
 117         n = fp->_p - p;         /* write this much */
 118
 119         /*
 120          * Set these immediately to avoid problems with longjmp and to allow
 121          * exchange buffering (via setvbuf) in user write function.
 122          */
 123         fp->_p = p;
 124         fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
 125
 126         for (; n > 0; n -= t, p += t) {
 127                 t = _swrite(fp, (char *)p, n);
 128                 if (t <= 0) {
 129                         fp->_flags |= __SERR;
 130                         return (EOF);
 131                 }
 132         }
 133         return (0);
 134 }
 135
 136 static int
 137 sflush_locked(FILE *fp)
 138 {
 139         int     ret;
 140
 141         FLOCKFILE(fp);
 142         ret = __sflush(fp);
 143         FUNLOCKFILE(fp);
 144         return (ret);
 145 }