fread.c revision 35129 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38#if 0
39static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
40#endif
41static const char rcsid[] =
42		"$Id: fread.c,v 1.5 1997/02/22 15:02:03 peter Exp $";
43#endif /* LIBC_SCCS and not lint */
44
45#include <stdio.h>
46#include <string.h>
47#include "local.h"
48#include "libc_private.h"
49
50size_t
51fread(buf, size, count, fp)
52	void *buf;
53	size_t size, count;
54	register FILE *fp;
55{
56	register size_t resid;
57	register char *p;
58	register int r;
59	size_t total;
60
61	/*
62	 * The ANSI standard requires a return value of 0 for a count
63	 * or a size of 0.  Peculiarily, it imposes no such requirements
64	 * on fwrite; it only requires fread to be broken.
65	 */
66	if ((resid = count * size) == 0)
67		return (0);
68	FLOCKFILE(fp);
69	if (fp->_r < 0)
70		fp->_r = 0;
71	total = resid;
72	p = buf;
73	while (resid > (r = fp->_r)) {
74		(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
75		fp->_p += r;
76		/* fp->_r = 0 ... done in __srefill */
77		p += r;
78		resid -= r;
79		if (__srefill(fp)) {
80			/* no more input: return partial result */
81			FUNLOCKFILE(fp);
82			return ((total - resid) / size);
83		}
84	}
85	(void)memcpy((void *)p, (void *)fp->_p, resid);
86	fp->_r -= resid;
87	fp->_p += resid;
88	FUNLOCKFILE(fp);
89	return (count);
90}
91