2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
7 * This code is derived from software contributed to Berkeley by
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14 * notice, this list of conditions and the following disclaimer.
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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("$FreeBSD$");
41 #include "namespace.h"
46 #include "un-namespace.h"
48 #include "libc_private.h"
55 fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
59 FLOCKFILE_CANCELSAFE(fp);
60 ret = __fread(buf, size, count, fp);
61 FUNLOCKFILE_CANCELSAFE();
66 __fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
74 * ANSI and SUSv2 require a return value of 0 if size or count are 0.
76 if ((count == 0) || (size == 0))
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).
85 if (((count | size) > 0xFFFF) &&
86 (count > SIZE_MAX / size)) {
93 * Compute the (now required to not overflow) number of bytes to
94 * read and actually do the work.
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.
108 if ((fp->_flags & __SNBF) != 0 && buf != NULL) {
110 /* set up the buffer */
111 fp->_bf._base = fp->_p = p;
112 fp->_bf._size = resid;
115 /* no more input: return partial result */
116 count = (total - resid) / size;
123 /* restore the old buffer (see __smakebuf) */
124 fp->_bf._base = fp->_p = fp->_nbuf;
131 while (resid > (r = fp->_r)) {
132 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
134 /* fp->_r = 0 ... done in __srefill */
138 /* no more input: return partial result */
139 return ((total - resid) / size);
142 (void)memcpy((void *)p, (void *)fp->_p, resid);
148 __weak_reference(__fread, fread_unlocked);