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fflush.c revision 1.20 
      1 /*	$NetBSD: fflush.c,v 1.20 2021/07/06 14:22:16 christos Exp $	*/
      2 
      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 #include <sys/cdefs.h>
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)fflush.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 __RCSID("$NetBSD: fflush.c,v 1.20 2021/07/06 14:22:16 christos Exp $");
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <stddef.h>
     45 #include <assert.h>
     46 #include <errno.h>
     47 #include <stdio.h>
     48 #include <string.h>
     49 
     50 #include "reentrant.h"
     51 #include "local.h"
     52 
     53 #ifdef _REENTRANT
     54 extern rwlock_t __sfp_lock;
     55 #endif
     56 
     57 /* Flush a single file, or (if fp is NULL) all files.  */
     58 int
     59 fflush(FILE *fp)
     60 {
     61 	int r;
     62 
     63 	if (fp == NULL) {
     64 		rwlock_rdlock(&__sfp_lock);
     65 		r = _fwalk(__sflush);
     66 		rwlock_unlock(&__sfp_lock);
     67 		return r;
     68 	}
     69 
     70 	FLOCKFILE(fp);
     71 	if ((fp->_flags & (__SWR | __SRW)) == 0) {
     72 		errno = EBADF;
     73 		r = EOF;
     74 	} else {
     75 		r = __sflush(fp);
     76 	}
     77 	FUNLOCKFILE(fp);
     78 	return r;
     79 }
     80 
     81 int
     82 __sflush(FILE *fp)
     83 {
     84 	unsigned char *p;
     85 	size_t n;
     86 	ssize_t t;
     87 
     88 	_DIAGASSERT(fp != NULL);
     89 
     90 	t = fp->_flags;
     91 	if ((t & __SWR) == 0)
     92 		return 0;
     93 
     94 	if ((p = fp->_bf._base) == NULL)
     95 		return 0;
     96 
     97 	ptrdiff_t tp = fp->_p - p;
     98 	_DIAGASSERT(__type_fit(ssize_t, tp));
     99 	n = (ssize_t)tp;	/* write this much */
    100 
    101 	/*
    102 	 * Set these immediately to avoid problems with longjmp and to allow
    103 	 * exchange buffering (via setvbuf) in user write function.
    104 	 */
    105 	fp->_p = p;
    106 	fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
    107 
    108 	for (; n > 0; n -= t, p += t) {
    109 		t = (*fp->_write)(fp->_cookie, (char *)p, n);
    110 		if (t < 0) {
    111 			if (errno == EINTR) {
    112 				t = 0;
    113 				continue;
    114 			}
    115 			/* Reset _p and _w. */
    116 			if (p > fp->_p) {
    117 				/* Some was written. */
    118 				memmove(fp->_p, p, n);
    119 				fp->_p += n;
    120 				if ((fp->_flags & (__SLBF | __SNBF)) == 0)
    121 					fp->_w -= n;
    122 			}
    123 			fp->_flags |= __SERR;
    124 			return EOF;
    125 		}
    126 	}
    127 	if (fp->_flush)
    128 		return (*fp->_flush)(fp->_cookie);
    129 	return 0;
    130 }
    131