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  * 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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)fflush.c    8.1 (Berkeley) 6/4/93";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/fflush.c,v 1.14 2007/01/09 00:28:06 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <errno.h>
  41 #include <stdio.h>
  42 #include <string.h>
  43 #include "un-namespace.h"
  44 #include "libc_private.h"
  45 #include "local.h"
  46
  47 static int      sflush_locked(FILE *);
  48
  49 /*
  50  * Flush a single file, or (if fp is NULL) all files.
  51  * MT-safe version
  52  */
  53 int
  54 fflush(FILE *fp)
  55 {
  56         int retval;
  57
  58         if (fp == NULL)
  59                 return (_fwalk(sflush_locked));
  60         FLOCKFILE(fp);
  61
  62         /*
  63          * 11103146: Conformance change:
  64          * --- Begin History ---
  65          * There is disagreement about the correct behaviour of fflush()
  66          * when passed a file which is not open for writing.  According to
  67          * the ISO C standard, the behaviour is undefined.
  68          * Under linux, such an fflush returns success and has no effect;
  69          * under Windows, such an fflush is documented as behaving instead
  70          * as fpurge().
  71          * Given that applications may be written with the expectation of
  72          * either of these two behaviours, the only safe (non-astonishing)
  73          * option is to return EBADF and ask that applications be fixed.
  74          * --- End History ---
  75          * SUSv3 now requires that fflush() returns success on a read-only
  76          * stream.  In addition, the conformance tests will warn if a fflush
  77          * on a read-only stream does not set the file descriptor's file offset
  78          * to the real position.  We won't be fixing the warning at this time.
  79          */
  80         if ((fp->_flags & (__SWR | __SRW)) == 0) {
  81                 retval = 0;
  82         } else
  83                 retval = __sflush(fp);
  84         FUNLOCKFILE(fp);
  85         return (retval);
  86 }
  87
  88 /*
  89  * Flush a single file, or (if fp is NULL) all files.
  90  * Non-MT-safe version
  91  */
  92 int
  93 __fflush(FILE *fp)
  94 {
  95         int retval;
  96
  97         if (fp == NULL)
  98                 return (_fwalk(sflush_locked));
  99         if ((fp->_flags & (__SWR | __SRW)) == 0) {
 100                 retval = 0;
 101         } else
 102                 retval = __sflush(fp);
 103         return (retval);
 104 }
 105
 106 int
 107 __sflush(FILE *fp)
 108 {
 109         unsigned char *p;
 110         int n, t;
 111
 112         t = fp->_flags;
 113         if ((t & __SWR) == 0)
 114                 return (0);
 115
 116         if ((p = fp->_bf._base) == NULL)
 117                 return (0);
 118
 119         n = fp->_p - p;         /* write this much */
 120
 121         /*
 122          * Set these immediately to avoid problems with longjmp and to allow
 123          * exchange buffering (via setvbuf) in user write function.
 124          */
 125         fp->_p = p;
 126         fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
 127
 128         for (; n > 0; n -= t, p += t) {
 129                 t = _swrite(fp, (char *)p, n);
 130                 if (t <= 0) {
 131                         /* 5340694: reset _p and _w on EAGAIN */
 132                         if (t < 0 && errno == EAGAIN) {
 133                                 if (p > fp->_p) /* some was written */
 134                                         memmove(fp->_p, p, n);
 135                                 fp->_p += n;
 136                                 if (!(fp->_flags & (__SLBF|__SNBF)))
 137                                         fp->_w -= n;
 138                         }
 139                         fp->_flags |= __SERR;
 140                         return (EOF);
 141                 }
 142         }
 143         return (0);
 144 }
 145
 146 static int
 147 sflush_locked(FILE *fp)
 148 {
 149         int     ret;
 150
 151         FLOCKFILE(fp);
 152         ret = __sflush(fp);
 153         FUNLOCKFILE(fp);
 154         return (ret);
 155 }