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 #include "namespace.h" 40 #include <errno.h> 41 #include <stdio.h> 42 #include "un-namespace.h" 43 #include "libc_private.h" 44 #include "local.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_CANCELSAFE(fp); 60 61 /* 62 * There is disagreement about the correct behaviour of fflush() 63 * when passed a file which is not open for writing. 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 * SUSv3 now requires that fflush() returns success on a read-only 72 * stream. 73 * 74 */ 75 if ((fp->_flags & (__SWR | __SRW)) == 0) 76 retval = 0; 77 else 78 retval = __sflush(fp); 79 FUNLOCKFILE_CANCELSAFE(); 80 return (retval); 81 } 82 83 /* 84 * Flush a single file, or (if fp is NULL) all files. 85 * Non-MT-safe version 86 */ 87 int 88 __fflush(FILE *fp) 89 { 90 int retval; 91 92 if (fp == NULL) 93 return (_fwalk(sflush_locked)); 94 if ((fp->_flags & (__SWR | __SRW)) == 0) 95 retval = 0; 96 else 97 retval = __sflush(fp); 98 return (retval); 99 } 100 101 __weak_reference(__fflush, fflush_unlocked); 102 103 int 104 __sflush(FILE *fp) 105 { 106 unsigned char *p, *old_p; 107 int n, t, old_w; 108 109 t = fp->_flags; 110 if ((t & __SWR) == 0) 111 return (0); 112 113 if ((p = fp->_bf._base) == NULL) 114 return (0); 115 116 n = fp->_p - p; /* write this much */ 117 118 /* 119 * Set these immediately to avoid problems with longjmp and to allow 120 * exchange buffering (via setvbuf) in user write function. 121 */ 122 old_p = fp->_p; 123 fp->_p = p; 124 old_w = fp->_w; 125 fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size; 126 127 for (; n > 0; n -= t, p += t) { 128 t = _swrite(fp, (char *)p, n); 129 if (t <= 0) { 130 /* Reset _p and _w. */ 131 if (p > fp->_p) { 132 /* Some was written. */ 133 memmove(fp->_p, p, n); 134 fp->_p += n; 135 if ((fp->_flags & (__SLBF | __SNBF)) == 0) 136 fp->_w -= n; 137 /* conditional to handle setvbuf */ 138 } else if (p == fp->_p && errno == EINTR) { 139 fp->_p = old_p; 140 fp->_w = old_w; 141 } 142 fp->_flags |= __SERR; 143 return (EOF); 144 } 145 } 146 return (0); 147 } 148 149 static int 150 sflush_locked(FILE *fp) 151 { 152 int ret; 153 154 FLOCKFILE_CANCELSAFE(fp); 155 ret = __sflush(fp); 156 FUNLOCKFILE_CANCELSAFE(); 157 return (ret); 158 } 159