1/* $NetBSD: fread.c,v 1.27 2024/01/20 14:52:49 christos Exp $ */ 2 3/*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35#include <sys/cdefs.h> 36#if defined(LIBC_SCCS) && !defined(lint) 37#if 0 38static char sccsid[] = "@(#)fread.c 8.2 (Berkeley) 12/11/93"; 39#else 40__RCSID("$NetBSD: fread.c,v 1.27 2024/01/20 14:52:49 christos Exp $"); 41#endif 42#endif /* LIBC_SCCS and not lint */ 43 44#include <assert.h> 45#include <errno.h> 46#include <stdio.h> 47#include <string.h> 48#include "reentrant.h" 49#include "local.h" 50 51#define MUL_NO_OVERFLOW (1UL << (sizeof(size_t) * 4)) 52 53size_t 54fread(void *buf, size_t size, size_t count, FILE *fp) 55{ 56 size_t resid; 57 char *p; 58 int r; 59 size_t total; 60 61 _DIAGASSERT(fp != NULL); 62 63 /* 64 * Extension: Catch integer overflow 65 */ 66 if ((size >= MUL_NO_OVERFLOW || count >= MUL_NO_OVERFLOW) && 67 size > 0 && count > SIZE_MAX / size) { 68 errno = EOVERFLOW; 69 fp->_flags |= __SERR; 70 return (0); 71 } 72 73 /* 74 * The ANSI standard requires a return value of 0 for a count 75 * or a size of 0. Whilst ANSI imposes no such requirements on 76 * fwrite, the SUSv2 does. 77 */ 78 if ((resid = count * size) == 0) 79 return 0; 80 81 _DIAGASSERT(buf != NULL); 82 83 FLOCKFILE(fp); 84 total = resid; 85 p = buf; 86 87 /* 88 * If we're unbuffered we know that the buffer in fp is empty so 89 * we can read directly into buf. This is much faster than a 90 * series of one byte reads into fp->_nbuf. 91 */ 92 if ((fp->_flags & __SNBF) != 0) { 93 while (resid > 0) { 94 /* set up the buffer */ 95 fp->_bf._base = fp->_p = (unsigned char *)p; 96 fp->_bf._size = (int)resid; 97 98 if (__srefill(fp)) { 99 /* no more input: return partial result */ 100 count = (total - resid) / size; 101 break; 102 } 103 p += fp->_r; 104 resid -= fp->_r; 105 } 106 107 /* restore the old buffer (see __smakebuf) */ 108 fp->_bf._base = fp->_p = fp->_nbuf; 109 fp->_bf._size = 1; 110 fp->_r = 0; 111 112 FUNLOCKFILE(fp); 113 return (count); 114 } 115 116 if (fp->_r <= 0) { 117 /* Nothing to read on enter, refill the buffers. */ 118 goto refill; 119 } 120 121 while (resid > (size_t)(r = fp->_r)) { 122 (void)memcpy(p, fp->_p, (size_t)r); 123 fp->_p += r; 124 /* fp->_r = 0 ... done in __srefill */ 125 p += r; 126 resid -= r; 127refill: 128 if (__srefill(fp)) { 129 /* no more input: return partial result */ 130 FUNLOCKFILE(fp); 131 return (total - resid) / size; 132 } 133 } 134 (void)memcpy(p, fp->_p, resid); 135 136 _DIAGASSERT(__type_fit(int, fp->_r - resid)); 137 fp->_r -= (int)resid; 138 fp->_p += resid; 139 FUNLOCKFILE(fp); 140 return count; 141} 142