1 /* $NetBSD: fread.c,v 1.24 2021/01/31 16:18:22 jdolecek 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 38 static char sccsid[] = "@(#)fread.c 8.2 (Berkeley) 12/11/93"; 39 #else 40 __RCSID("$NetBSD: fread.c,v 1.24 2021/01/31 16:18:22 jdolecek 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 size_t 52 fread(void *buf, size_t size, size_t count, FILE *fp) 53 { 54 size_t resid; 55 char *p; 56 int r; 57 size_t total; 58 59 _DIAGASSERT(fp != NULL); 60 /* 61 * The ANSI standard requires a return value of 0 for a count 62 * or a size of 0. Whilst ANSI imposes no such requirements on 63 * fwrite, the SUSv2 does. 64 */ 65 if ((resid = count * size) == 0) 66 return 0; 67 68 _DIAGASSERT(buf != NULL); 69 70 FLOCKFILE(fp); 71 if (fp->_r < 0) 72 fp->_r = 0; 73 total = resid; 74 p = buf; 75 76 /* 77 * If we're unbuffered we know that the buffer in fp is empty so 78 * we can read directly into buf. This is much faster than a 79 * series of one byte reads into fp->_nbuf. 80 */ 81 if ((fp->_flags & __SNBF) != 0) { 82 while (resid > 0) { 83 /* set up the buffer */ 84 fp->_bf._base = fp->_p = (unsigned char *)p; 85 fp->_bf._size = resid; 86 87 if (__srefill(fp)) { 88 /* no more input: return partial result */ 89 count = (total - resid) / size; 90 break; 91 } 92 p += fp->_r; 93 resid -= fp->_r; 94 } 95 96 /* restore the old buffer (see __smakebuf) */ 97 fp->_bf._base = fp->_p = fp->_nbuf; 98 fp->_bf._size = 1; 99 fp->_r = 0; 100 101 FUNLOCKFILE(fp); 102 return (count); 103 } 104 105 while (resid > (size_t)(r = fp->_r)) { 106 (void)memcpy(p, fp->_p, (size_t)r); 107 fp->_p += r; 108 /* fp->_r = 0 ... done in __srefill */ 109 p += r; 110 resid -= r; 111 if (__srefill(fp)) { 112 /* no more input: return partial result */ 113 FUNLOCKFILE(fp); 114 return (total - resid) / size; 115 } 116 } 117 (void)memcpy(p, fp->_p, resid); 118 119 _DIAGASSERT(__type_fit(int, fp->_r - resid)); 120 fp->_r -= (int)resid; 121 fp->_p += resid; 122 FUNLOCKFILE(fp); 123 return count; 124 } 125