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  * 4. 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  * $DragonFly: src/lib/libc/stdio/fflush.c,v 1.6 2005/07/23 20:23:05 joerg Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <errno.h>
  39 #include <stdio.h>
  40 #include "un-namespace.h"
  41 #include "libc_private.h"
  42
  43 #include "local.h"
  44 #include "priv_stdio.h"
  45
  46 static int      sflush_locked(FILE *);
  47
  48 /*
  49  * Flush a single file, or (if fp is NULL) all files.
  50  * MT-safe version
  51  */
  52 int
  53 fflush(FILE *fp)
  54 {
  55         int retval;
  56
  57         if (fp == NULL)
  58                 return (_fwalk(sflush_locked));
  59         FLOCKFILE(fp);
  60
  61         /*
  62          * There is disagreement about the correct behaviour of fflush()
  63          * when passed a file which is not open for reading.  According to
  64          * the ISO C standard, the behaviour is undefined.
  65          * Under linux, such an fflush returns success and has no effect;
  66          * under Windows, such an fflush is documented as behaving instead
  67          * as fpurge().
  68          * Given that applications may be written with the expectation of
  69          * either of these two behaviours, the only safe (non-astonishing)
  70          * option is to return EBADF and ask that applications be fixed.
  71          */
  72         if ((fp->pub._flags & (__SWR | __SRW)) == 0) {
  73                 errno = EBADF;
  74                 retval = EOF;
  75         } else {
  76                 retval = __sflush(fp);
  77         }
  78         FUNLOCKFILE(fp);
  79         return (retval);
  80 }
  81
  82 /*
  83  * Flush a single file, or (if fp is NULL) all files.
  84  * Non-MT-safe version
  85  */
  86 int
  87 __fflush(FILE *fp)
  88 {
  89         int retval;
  90
  91         if (fp == NULL)
  92                 return (_fwalk(sflush_locked));
  93         if ((fp->pub._flags & (__SWR | __SRW)) == 0) {
  94                 errno = EBADF;
  95                 retval = EOF;
  96         } else {
  97                 retval = __sflush(fp);
  98         }
  99         return (retval);
 100 }
 101
 102 int
 103 __sflush(FILE *fp)
 104 {
 105         unsigned char *p;
 106         int n, t;
 107
 108         t = fp->pub._flags;
 109         if ((t & __SWR) == 0)
 110                 return (0);
 111
 112         if ((p = fp->_bf._base) == NULL)
 113                 return (0);
 114
 115         n = fp->pub._p - p;     /* write this much */
 116
 117         /*
 118          * Set these immediately to avoid problems with longjmp and to allow
 119          * exchange buffering (via setvbuf) in user write function.
 120          */
 121         fp->pub._p = p;
 122         fp->pub._w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
 123
 124         for (; n > 0; n -= t, p += t) {
 125                 t = _swrite(fp, (char *)p, n);
 126                 if (t <= 0) {
 127                         fp->pub._flags |= __SERR;
 128                         return (EOF);
 129                 }
 130         }
 131         return (0);
 132 }
 133
 134 static int
 135 sflush_locked(FILE *fp)
 136 {
 137         int     ret;
 138
 139         FLOCKFILE(fp);
 140         ret = __sflush(fp);
 141         FUNLOCKFILE(fp);
 142         return (ret);
 143 }