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/* $OpenBSD: fread.c,v 1.12 2014/05/01 16:40:36 deraadt 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 <sys/param.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)
{
/*
* 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);
}
const size_t desired_total = count * size;
size_t total = desired_total;
/*
* ANSI and SUSv2 require a return value of 0 if size or count are 0.
*/
if (total == 0) {
return (0);
}
FLOCKFILE(fp);
_SET_ORIENTATION(fp, -1);
// TODO: how can this ever happen?!
if (fp->_r < 0)
fp->_r = 0;
/*
* Ensure _bf._size is valid.
*/
if (fp->_bf._base == NULL) {
__smakebuf(fp);
}
char* dst = buf;
while (total > 0) {
/*
* Copy data out of the buffer.
*/
size_t buffered_bytes = MIN((size_t) fp->_r, total);
memcpy(dst, fp->_p, buffered_bytes);
fp->_p += buffered_bytes;
fp->_r -= buffered_bytes;
dst += buffered_bytes;
total -= buffered_bytes;
/*
* Are we done?
*/
if (total == 0) {
goto out;
}
/*
* Do we have so much more to read that we should
* avoid copying it through the buffer?
*/
if (total > (size_t) fp->_bf._size) {
/*
* Make sure that fseek doesn't think it can
* reuse the buffer since we are going to read
* directly from the file descriptor.
*/
fp->_flags |= __SMOD;
break;
}
/*
* Less than a buffer to go, so refill the buffer and
* go around the loop again.
*/
if (__srefill(fp)) {
goto out;
}
}
/*
* Read directly into the caller's buffer.
*/
while (total > 0) {
ssize_t bytes_read = (*fp->_read)(fp->_cookie, dst, total);
if (bytes_read <= 0) {
fp->_flags |= (bytes_read == 0) ? __SEOF : __SERR;
break;
}
dst += bytes_read;
total -= bytes_read;
}
out:
FUNLOCKFILE(fp);
return ((desired_total - total) / size);
}
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