xref: /freebsd/lib/libc/stdio/fread.c (revision 9768746b)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
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 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40 
41 #include "namespace.h"
42 #include <errno.h>
43 #include <stdint.h>
44 #include <stdio.h>
45 #include <string.h>
46 #include "un-namespace.h"
47 #include "local.h"
48 #include "libc_private.h"
49 
50 /*
51  * MT-safe version
52  */
53 
54 size_t
55 fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
56 {
57 	size_t ret;
58 
59 	FLOCKFILE_CANCELSAFE(fp);
60 	ret = __fread(buf, size, count, fp);
61 	FUNLOCKFILE_CANCELSAFE();
62 	return (ret);
63 }
64 
65 size_t
66 __fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
67 {
68 	size_t resid;
69 	char *p;
70 	int r;
71 	size_t total;
72 
73 	/*
74 	 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
75 	 */
76 	if ((count == 0) || (size == 0))
77 		return (0);
78 
79 	/*
80 	 * Check for integer overflow.  As an optimization, first check that
81 	 * at least one of {count, size} is at least 2^16, since if both
82 	 * values are less than that, their product can't possible overflow
83 	 * (size_t is always at least 32 bits on FreeBSD).
84 	 */
85 	if (((count | size) > 0xFFFF) &&
86 	    (count > SIZE_MAX / size)) {
87 		errno = EINVAL;
88 		fp->_flags |= __SERR;
89 		return (0);
90 	}
91 
92 	/*
93 	 * Compute the (now required to not overflow) number of bytes to
94 	 * read and actually do the work.
95 	 */
96 	resid = count * size;
97 	ORIENT(fp, -1);
98 	if (fp->_r < 0)
99 		fp->_r = 0;
100 	total = resid;
101 	p = buf;
102 
103 	/*
104 	 * If we're unbuffered we know that the buffer in fp is empty so
105 	 * we can read directly into buf.  This is much faster than a
106 	 * series of one byte reads into fp->_nbuf.
107 	 */
108 	if ((fp->_flags & __SNBF) != 0 && buf != NULL) {
109 		while (resid > 0) {
110 			/* set up the buffer */
111 			fp->_bf._base = fp->_p = p;
112 			fp->_bf._size = resid;
113 
114 			if (__srefill(fp)) {
115 				/* no more input: return partial result */
116 				count = (total - resid) / size;
117 				break;
118 			}
119 			p += fp->_r;
120 			resid -= fp->_r;
121 		}
122 
123 		/* restore the old buffer (see __smakebuf) */
124 		fp->_bf._base = fp->_p = fp->_nbuf;
125 		fp->_bf._size = 1;
126 		fp->_r = 0;
127 
128 		return (count);
129 	}
130 
131 	while (resid > (r = fp->_r)) {
132 		if (r != 0) {
133 			(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
134 			fp->_p += r;
135 			/* fp->_r = 0 ... done in __srefill */
136 			p += r;
137 			resid -= r;
138 		}
139 		if (__srefill(fp)) {
140 			/* no more input: return partial result */
141 			return ((total - resid) / size);
142 		}
143 	}
144 	(void)memcpy((void *)p, (void *)fp->_p, resid);
145 	fp->_r -= resid;
146 	fp->_p += resid;
147 	return (count);
148 }
149 
150 __weak_reference(__fread, fread_unlocked);
151