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/* $OpenBSD: fread.c,v 1.15 2016/09/21 04:38:56 guenther 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 "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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size_t resid; |
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char *p; |
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int r; |
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size_t total; |
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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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/* |
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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 ((resid = count * size) == 0) |
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return (0); |
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FLOCKFILE(fp); |
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_SET_ORIENTATION(fp, -1); |
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if (fp->_r < 0) |
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fp->_r = 0; |
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total = resid; |
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p = buf; |
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if ((fp->_flags & __SNBF) != 0) { |
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/* |
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* We know if we're unbuffered that our buffer is empty, so |
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* we can just read directly. This is much faster than the |
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* loop below which will perform a series of one byte reads. |
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*/ |
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while (resid > 0 && (r = (*fp->_read)(fp->_cookie, p, resid)) > 0) { |
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p += r; |
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resid -= r; |
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} |
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FUNLOCKFILE(fp); |
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return ((total - resid) / size); |
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} |
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while (resid > (r = fp->_r)) { |
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(void)memcpy(p, fp->_p, r); |
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fp->_p += r; |
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/* fp->_r = 0 ... done in __srefill */ |
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p += r; |
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resid -= r; |
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if (__srefill(fp)) { |
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/* no more input: return partial result */ |
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FUNLOCKFILE(fp); |
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return ((total - resid) / size); |
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} |
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} |
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(void)memcpy(p, fp->_p, resid); |
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fp->_r -= resid; |
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fp->_p += resid; |
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FUNLOCKFILE(fp); |
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return (count); |
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} |
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DEF_STRONG(fread); |