fread.c revision 165903 
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 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/stdio/fread.c 165903 2007-01-09 00:28:16Z imp $");
38
39#include "namespace.h"
40#include <stdio.h>
41#include <string.h>
42#include "un-namespace.h"
43#include "local.h"
44#include "libc_private.h"
45
46/*
47 * MT-safe version
48 */
49
50size_t
51fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
52{
53	int ret;
54
55	FLOCKFILE(fp);
56	ret = __fread(buf, size, count, fp);
57	FUNLOCKFILE(fp);
58	return (ret);
59}
60
61size_t
62__fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
63{
64	size_t resid;
65	char *p;
66	int r;
67	size_t total;
68
69	/*
70	 * The ANSI standard requires a return value of 0 for a count
71	 * or a size of 0.  Peculiarily, it imposes no such requirements
72	 * on fwrite; it only requires fread to be broken.
73	 */
74	if ((resid = count * size) == 0)
75		return (0);
76	ORIENT(fp, -1);
77	if (fp->_r < 0)
78		fp->_r = 0;
79	total = resid;
80	p = buf;
81	while (resid > (r = fp->_r)) {
82		(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
83		fp->_p += r;
84		/* fp->_r = 0 ... done in __srefill */
85		p += r;
86		resid -= r;
87		if (__srefill(fp)) {
88			/* no more input: return partial result */
89			return ((total - resid) / size);
90		}
91	}
92	(void)memcpy((void *)p, (void *)fp->_p, resid);
93	fp->_r -= resid;
94	fp->_p += resid;
95	return (count);
96}
97