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      1 /*	$NetBSD: fflush.c,v 1.24 2021/07/22 17:09:01 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 1.24 2021/07/22 17:09:01 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 "reentrant.h"
     49 #include "local.h"
     50 
     51 #ifdef _REENTRANT
     52 extern rwlock_t __sfp_lock;
     53 #endif
     54 
     55 /* Flush a single file, or (if fp is NULL) all files.  */
     56 int
     57 fflush(FILE *fp)
     58 {
     59 	int r;
     60 
     61 	if (fp == NULL) {
     62 		rwlock_rdlock(&__sfp_lock);
     63 		r = _fwalk(__sflush);
     64 		rwlock_unlock(&__sfp_lock);
     65 		return r;
     66 	}
     67 
     68 	FLOCKFILE(fp);
     69 	if ((fp->_flags & (__SWR | __SRW)) == 0) {
     70 		errno = EBADF;
     71 		r = EOF;
     72 	} else {
     73 		r = __sflush(fp);
     74 	}
     75 	FUNLOCKFILE(fp);
     76 	return r;
     77 }
     78 
     79 int
     80 __sflush(FILE *fp)
     81 {
     82 	unsigned char *p;
     83 	size_t n;
     84 	ssize_t t;
     85 
     86 	_DIAGASSERT(fp != NULL);
     87 
     88 	t = fp->_flags;
     89 	if ((t & __SWR) == 0)
     90 		return 0;
     91 
     92 	if ((p = fp->_bf._base) == NULL)
     93 		return 0;
     94 
     95 	ptrdiff_t tp = fp->_p - p;
     96 	_DIAGASSERT(__type_fit(ssize_t, tp));
     97 	n = (ssize_t)tp;	/* write this much */
     98 
     99 	/*
    100 	 * Set these immediately to avoid problems with longjmp and to allow
    101 	 * exchange buffering (via setvbuf) in user write function.
    102 	 */
    103 	fp->_p = p;
    104 	fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
    105 
    106 	for (; n > 0; n -= t, p += t) {
    107 		t = (*fp->_write)(fp->_cookie, (char *)p, n);
    108 		if (t <= 0) {
    109 			fp->_flags |= __SERR;
    110 			return EOF;
    111 		}
    112 	}
    113 	if (fp->_flush)
    114 		return (*fp->_flush)(fp->_cookie);
    115 	return 0;
    116 }
    117