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 "namespace.h" 39 #include <errno.h> 40 #include <stdio.h> 41 #include "un-namespace.h" 42 #include "libc_private.h" 43 #include "local.h" 44 45 static int sflush_locked(FILE *); 46 47 /* 48 * Flush a single file, or (if fp is NULL) all files. 49 * MT-safe version 50 */ 51 int 52 fflush(FILE *fp) 53 { 54 int retval; 55 56 if (fp == NULL) 57 return (_fwalk(sflush_locked)); 58 FLOCKFILE_CANCELSAFE(fp); 59 60 /* 61 * There is disagreement about the correct behaviour of fflush() 62 * when passed a file which is not open for writing. According to 63 * the ISO C standard, the behaviour is undefined. 64 * Under linux, such an fflush returns success and has no effect; 65 * under Windows, such an fflush is documented as behaving instead 66 * as fpurge(). 67 * Given that applications may be written with the expectation of 68 * either of these two behaviours, the only safe (non-astonishing) 69 * option is to return EBADF and ask that applications be fixed. 70 * SUSv3 now requires that fflush() returns success on a read-only 71 * stream. 72 * 73 */ 74 if ((fp->_flags & (__SWR | __SRW)) == 0) 75 retval = 0; 76 else 77 retval = __sflush(fp); 78 FUNLOCKFILE_CANCELSAFE(); 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->_flags & (__SWR | __SRW)) == 0) 94 retval = 0; 95 else 96 retval = __sflush(fp); 97 return (retval); 98 } 99 100 __weak_reference(__fflush, fflush_unlocked); 101 102 int 103 __sflush(FILE *fp) 104 { 105 unsigned char *p; 106 int n, f, t; 107 108 f = fp->_flags; 109 if ((f & __SWR) == 0) 110 return (0); 111 112 if ((p = fp->_bf._base) == NULL) 113 return (0); 114 115 n = fp->_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->_p = p; 122 fp->_w = f & (__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 if (p > fp->_p) 128 /* Some was written. */ 129 memmove(fp->_p, p, n); 130 /* Reset _p and _w. */ 131 fp->_p += n; 132 if ((fp->_flags & __SNBF) == 0) 133 fp->_w -= n; 134 fp->_flags |= __SERR; 135 return (EOF); 136 } 137 } 138 return (0); 139 } 140 141 static int 142 sflush_locked(FILE *fp) 143 { 144 int ret; 145 146 FLOCKFILE_CANCELSAFE(fp); 147 ret = __sflush(fp); 148 FUNLOCKFILE_CANCELSAFE(); 149 return (ret); 150 } 151