140 lines
3.7 KiB
C
140 lines
3.7 KiB
C
/* $OpenBSD: fread.c,v 1.12 2014/05/01 16:40:36 deraadt Exp $ */
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/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdint.h>
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#include <errno.h>
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#include <sys/param.h>
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#include "local.h"
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#define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4))
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size_t
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fread(void *buf, size_t size, size_t count, FILE *fp)
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{
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/*
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* Extension: Catch integer overflow.
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*/
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if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) &&
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size > 0 && SIZE_MAX / size < count) {
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errno = EOVERFLOW;
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fp->_flags |= __SERR;
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return (0);
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}
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const size_t desired_total = count * size;
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size_t total = desired_total;
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/*
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* ANSI and SUSv2 require a return value of 0 if size or count are 0.
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*/
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if (total == 0) {
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return (0);
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}
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FLOCKFILE(fp);
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_SET_ORIENTATION(fp, -1);
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// TODO: how can this ever happen?!
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if (fp->_r < 0)
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fp->_r = 0;
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/*
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* Ensure _bf._size is valid.
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*/
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if (fp->_bf._base == NULL) {
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__smakebuf(fp);
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}
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char* dst = buf;
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while (total > 0) {
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/*
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* Copy data out of the buffer.
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*/
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size_t buffered_bytes = MIN((size_t) fp->_r, total);
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memcpy(dst, fp->_p, buffered_bytes);
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fp->_p += buffered_bytes;
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fp->_r -= buffered_bytes;
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dst += buffered_bytes;
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total -= buffered_bytes;
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/*
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* Are we done?
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*/
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if (total == 0) {
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goto out;
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}
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/*
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* Do we have so much more to read that we should
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* avoid copying it through the buffer?
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*/
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if (total > (size_t) fp->_bf._size) {
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/*
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* Make sure that fseek doesn't think it can
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* reuse the buffer since we are going to read
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* directly from the file descriptor.
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*/
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fp->_flags |= __SMOD;
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break;
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}
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/*
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* Less than a buffer to go, so refill the buffer and
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* go around the loop again.
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*/
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if (__srefill(fp)) {
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goto out;
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}
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}
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/*
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* Read directly into the caller's buffer.
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*/
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while (total > 0) {
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ssize_t bytes_read = (*fp->_read)(fp->_cookie, dst, total);
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if (bytes_read <= 0) {
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fp->_flags |= (bytes_read == 0) ? __SEOF : __SERR;
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break;
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}
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dst += bytes_read;
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total -= bytes_read;
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}
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out:
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FUNLOCKFILE(fp);
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return ((desired_total - total) / size);
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}
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