lib/libc/stdio/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. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)fflush.c 8.1 (Berkeley) 6/4/93
  33  * $FreeBSD: src/lib/libc/stdio/fflush.c,v 1.14 2007/01/09 00:28:06 imp Exp $
  34  */
  35
  36 #include "namespace.h"
  37 #include <errno.h>
  38 #include <stdio.h>
  39 #include "un-namespace.h"
  40 #include "libc_private.h"
  41
  42 #include "local.h"
  43
  44 static int      sflush_locked(FILE *);
  45
  46 /*
  47  * Flush a single file, or (if fp is NULL) all files.
  48  * MT-safe version
  49  */
  50 int
  51 fflush(FILE *fp)
  52 {
  53         int retval;
  54
  55         if (fp == NULL)
  56                 return (_fwalk(sflush_locked));
  57         FLOCKFILE(fp);
  58
  59         /*
  60          * There is disagreement about the correct behaviour of fflush()
  61          * when passed a file which is not open for reading.  According to
  62          * the ISO C standard, the behaviour is undefined.
  63          * Under linux, such an fflush returns success and has no effect;
  64          * under Windows, such an fflush is documented as behaving instead
  65          * as fpurge().
  66          * Given that applications may be written with the expectation of
  67          * either of these two behaviours, the only safe (non-astonishing)
  68          * option is to return EBADF and ask that applications be fixed.
  69          * But for c++ compatibility do not enforce it and match FreeBSD.
  70          */
  71         if ((fp->pub._flags & (__SWR | __SRW)) == 0)
  72                 retval = 0;
  73         else
  74                 retval = __sflush(fp);
  75         FUNLOCKFILE(fp);
  76         return (retval);
  77 }
  78
  79 /*
  80  * Flush a single file, or (if fp is NULL) all files.
  81  * Non-MT-safe version
  82  */
  83 int
  84 __fflush(FILE *fp)
  85 {
  86         int retval;
  87
  88         if (fp == NULL)
  89                 return (_fwalk(sflush_locked));
  90         if ((fp->pub._flags & (__SWR | __SRW)) == 0)
  91                 retval = 0;
  92         else
  93                 retval = __sflush(fp);
  94         return (retval);
  95 }
  96
  97 int
  98 __sflush(FILE *fp)
  99 {
 100         unsigned char *p;
 101         int n, t;
 102
 103         t = fp->pub._flags;
 104         if ((t & __SWR) == 0)
 105                 return (0);
 106
 107         if ((p = fp->_bf._base) == NULL)
 108                 return (0);
 109
 110         n = fp->pub._p - p;     /* write this much */
 111
 112         /*
 113          * Set these immediately to avoid problems with longjmp and to allow
 114          * exchange buffering (via setvbuf) in user write function.
 115          */
 116         fp->pub._p = p;
 117         fp->pub._w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
 118
 119         for (; n > 0; n -= t, p += t) {
 120                 t = _swrite(fp, (char *)p, n);
 121                 if (t <= 0) {
 122                         /* Reset _p and _w. */
 123                         if (p > fp->pub._p) {
 124                                 /* Some was written. */
 125                                 memmove(fp->pub._p, p, n);
 126                                 fp->pub._p += n;
 127                                 if ((fp->pub._flags & (__SLBF | __SNBF)) == 0)
 128                                         fp->pub._w -= n;
 129                         }
 130                         fp->pub._flags |= __SERR;
 131                         return (EOF);
 132                 }
 133         }
 134         return (0);
 135 }
 136
 137 static int
 138 sflush_locked(FILE *fp)
 139 {
 140         int     ret;
 141
 142         FLOCKFILE(fp);
 143         ret = __sflush(fp);
 144         FUNLOCKFILE(fp);
 145         return (ret);
 146 }