xref: /minix3/lib/libc/stdio/fread.c (revision f14fb602092e015ff630df58e17c2a9cd57d29b3)
1*f14fb602SLionel Sambuc /*	$NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos Exp $	*/
2b7061124SArun Thomas 
32fe8fb19SBen Gras /*-
42fe8fb19SBen Gras  * Copyright (c) 1990, 1993
52fe8fb19SBen Gras  *	The Regents of the University of California.  All rights reserved.
62fe8fb19SBen Gras  *
72fe8fb19SBen Gras  * This code is derived from software contributed to Berkeley by
82fe8fb19SBen Gras  * Chris Torek.
92fe8fb19SBen Gras  *
102fe8fb19SBen Gras  * Redistribution and use in source and binary forms, with or without
112fe8fb19SBen Gras  * modification, are permitted provided that the following conditions
122fe8fb19SBen Gras  * are met:
132fe8fb19SBen Gras  * 1. Redistributions of source code must retain the above copyright
142fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer.
152fe8fb19SBen Gras  * 2. Redistributions in binary form must reproduce the above copyright
162fe8fb19SBen Gras  *    notice, this list of conditions and the following disclaimer in the
172fe8fb19SBen Gras  *    documentation and/or other materials provided with the distribution.
182fe8fb19SBen Gras  * 3. Neither the name of the University nor the names of its contributors
192fe8fb19SBen Gras  *    may be used to endorse or promote products derived from this software
202fe8fb19SBen Gras  *    without specific prior written permission.
212fe8fb19SBen Gras  *
222fe8fb19SBen Gras  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
232fe8fb19SBen Gras  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
242fe8fb19SBen Gras  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
252fe8fb19SBen Gras  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
262fe8fb19SBen Gras  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
272fe8fb19SBen Gras  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
282fe8fb19SBen Gras  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
292fe8fb19SBen Gras  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
302fe8fb19SBen Gras  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
312fe8fb19SBen Gras  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
322fe8fb19SBen Gras  * SUCH DAMAGE.
332fe8fb19SBen Gras  */
342fe8fb19SBen Gras 
352fe8fb19SBen Gras #include <sys/cdefs.h>
362fe8fb19SBen Gras #if defined(LIBC_SCCS) && !defined(lint)
372fe8fb19SBen Gras #if 0
382fe8fb19SBen Gras static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
392fe8fb19SBen Gras #else
40*f14fb602SLionel Sambuc __RCSID("$NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos Exp $");
412fe8fb19SBen Gras #endif
422fe8fb19SBen Gras #endif /* LIBC_SCCS and not lint */
432fe8fb19SBen Gras 
442fe8fb19SBen Gras #include <assert.h>
452fe8fb19SBen Gras #include <errno.h>
46b7061124SArun Thomas #include <stdio.h>
472fe8fb19SBen Gras #include <string.h>
482fe8fb19SBen Gras #include "reentrant.h"
492fe8fb19SBen Gras #include "local.h"
50b7061124SArun Thomas 
51b7061124SArun Thomas size_t
fread(void * buf,size_t size,size_t count,FILE * fp)52*f14fb602SLionel Sambuc fread(void *buf, size_t size, size_t count, FILE *fp)
53b7061124SArun Thomas {
542fe8fb19SBen Gras 	size_t resid;
552fe8fb19SBen Gras 	char *p;
562fe8fb19SBen Gras 	int r;
572fe8fb19SBen Gras 	size_t total;
58b7061124SArun Thomas 
592fe8fb19SBen Gras 	_DIAGASSERT(fp != NULL);
602fe8fb19SBen Gras 	/*
612fe8fb19SBen Gras 	 * The ANSI standard requires a return value of 0 for a count
622fe8fb19SBen Gras 	 * or a size of 0.  Whilst ANSI imposes no such requirements on
632fe8fb19SBen Gras 	 * fwrite, the SUSv2 does.
642fe8fb19SBen Gras 	 */
652fe8fb19SBen Gras 	if ((resid = count * size) == 0)
66*f14fb602SLionel Sambuc 		return 0;
672fe8fb19SBen Gras 
682fe8fb19SBen Gras 	_DIAGASSERT(buf != NULL);
692fe8fb19SBen Gras 
702fe8fb19SBen Gras 	FLOCKFILE(fp);
712fe8fb19SBen Gras 	if (fp->_r < 0)
722fe8fb19SBen Gras 		fp->_r = 0;
732fe8fb19SBen Gras 	total = resid;
742fe8fb19SBen Gras 	p = buf;
752fe8fb19SBen Gras 	while (resid > (size_t)(r = fp->_r)) {
762fe8fb19SBen Gras 		(void)memcpy(p, fp->_p, (size_t)r);
772fe8fb19SBen Gras 		fp->_p += r;
782fe8fb19SBen Gras 		/* fp->_r = 0 ... done in __srefill */
792fe8fb19SBen Gras 		p += r;
802fe8fb19SBen Gras 		resid -= r;
812fe8fb19SBen Gras 		if (__srefill(fp)) {
822fe8fb19SBen Gras 			/* no more input: return partial result */
832fe8fb19SBen Gras 			FUNLOCKFILE(fp);
84*f14fb602SLionel Sambuc 			return (total - resid) / size;
85b7061124SArun Thomas 		}
862fe8fb19SBen Gras 	}
872fe8fb19SBen Gras 	(void)memcpy(p, fp->_p, resid);
88*f14fb602SLionel Sambuc 
89*f14fb602SLionel Sambuc 	_DIAGASSERT(__type_fit(int, fp->_r - resid));
90*f14fb602SLionel Sambuc 	fp->_r -= (int)resid;
912fe8fb19SBen Gras 	fp->_p += resid;
922fe8fb19SBen Gras 	FUNLOCKFILE(fp);
93*f14fb602SLionel Sambuc 	return count;
94b7061124SArun Thomas }
95