1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)fflush.c 8.1 (Berkeley) 6/4/93"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include "namespace.h" 42 #include <errno.h> 43 #include <stdio.h> 44 #include "un-namespace.h" 45 #include "libc_private.h" 46 #include "local.h" 47 48 static int sflush_locked(FILE *); 49 50 /* 51 * Flush a single file, or (if fp is NULL) all files. 52 * MT-safe version 53 */ 54 int 55 fflush(FILE *fp) 56 { 57 int retval; 58 59 if (fp == NULL) 60 return (_fwalk(sflush_locked)); 61 FLOCKFILE_CANCELSAFE(fp); 62 63 /* 64 * There is disagreement about the correct behaviour of fflush() 65 * when passed a file which is not open for writing. According to 66 * the ISO C standard, the behaviour is undefined. 67 * Under linux, such an fflush returns success and has no effect; 68 * under Windows, such an fflush is documented as behaving instead 69 * as fpurge(). 70 * Given that applications may be written with the expectation of 71 * either of these two behaviours, the only safe (non-astonishing) 72 * option is to return EBADF and ask that applications be fixed. 73 * SUSv3 now requires that fflush() returns success on a read-only 74 * stream. 75 * 76 */ 77 if ((fp->_flags & (__SWR | __SRW)) == 0) 78 retval = 0; 79 else 80 retval = __sflush(fp); 81 FUNLOCKFILE_CANCELSAFE(); 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 retval = 0; 98 else 99 retval = __sflush(fp); 100 return (retval); 101 } 102 103 __weak_reference(__fflush, fflush_unlocked); 104 105 int 106 __sflush(FILE *fp) 107 { 108 unsigned char *p, *old_p; 109 int n, t, old_w; 110 111 t = fp->_flags; 112 if ((t & __SWR) == 0) 113 return (0); 114 115 if ((p = fp->_bf._base) == NULL) 116 return (0); 117 118 n = fp->_p - p; /* write this much */ 119 120 /* 121 * Set these immediately to avoid problems with longjmp and to allow 122 * exchange buffering (via setvbuf) in user write function. 123 */ 124 old_p = fp->_p; 125 fp->_p = p; 126 old_w = fp->_w; 127 fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size; 128 129 for (; n > 0; n -= t, p += t) { 130 t = _swrite(fp, (char *)p, n); 131 if (t <= 0) { 132 /* Reset _p and _w. */ 133 if (p > fp->_p) { 134 /* Some was written. */ 135 memmove(fp->_p, p, n); 136 fp->_p += n; 137 if ((fp->_flags & (__SLBF | __SNBF)) == 0) 138 fp->_w -= n; 139 } else if (p == fp->_p) { /* cond. to handle setvbuf */ 140 fp->_p = old_p; 141 fp->_w = old_w; 142 } 143 fp->_flags |= __SERR; 144 return (EOF); 145 } 146 } 147 return (0); 148 } 149 150 static int 151 sflush_locked(FILE *fp) 152 { 153 int ret; 154 155 FLOCKFILE_CANCELSAFE(fp); 156 ret = __sflush(fp); 157 FUNLOCKFILE_CANCELSAFE(); 158 return (ret); 159 } 160