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/* $OpenBSD: fread.c,v 1.17 2018/12/14 20:55:17 millert Exp $ */
/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>
#include "local.h"
#define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
size_t
fread(void *buf, size_t size, size_t count, FILE *fp)
{
size_t resid;
char *p;
int r;
size_t total;
/*
* Extension: Catch integer overflow
*/
if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) &&
size > 0 && SIZE_MAX / size < count) {
errno = EOVERFLOW;
fp->_flags |= __SERR;
return (0);
}
/*
* ANSI and SUSv2 require a return value of 0 if size or count are 0.
*/
if ((resid = count * size) == 0)
return (0);
FLOCKFILE(fp);
_SET_ORIENTATION(fp, -1);
if (fp->_r < 0)
fp->_r = 0;
total = resid;
p = buf;
/*
* If we're unbuffered we know that the buffer in fp is empty so
* we can read directly into buf. This is much faster than a
* series of one byte reads into fp->_nbuf.
*/
if ((fp->_flags & __SNBF) != 0 && buf != NULL) {
/* set up the buffer */
fp->_bf._base = fp->_p = buf;
fp->_bf._size = total;
while (resid > 0) {
if (__srefill(fp)) {
/* no more input: return partial result */
count = (total - resid) / size;
break;
}
fp->_p += fp->_r;
resid -= fp->_r;
}
/* restore the old buffer (see __smakebuf) */
fp->_bf._base = fp->_p = fp->_nbuf;
fp->_bf._size = 1;
fp->_r = 0;
FUNLOCKFILE(fp);
return (count);
}
while (resid > (r = fp->_r)) {
(void)memcpy(p, fp->_p, r);
fp->_p += r;
/* fp->_r = 0 ... done in __srefill */
p += r;
resid -= r;
if (__srefill(fp)) {
/* no more input: return partial result */
FUNLOCKFILE(fp);
return ((total - resid) / size);
}
}
(void)memcpy(p, fp->_p, resid);
fp->_r -= resid;
fp->_p += resid;
FUNLOCKFILE(fp);
return (count);
}
DEF_STRONG(fread);
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