1 /* $OpenBSD: fread.c,v 1.6 2005/08/08 08:05:36 espie Exp $ */ 2 /*- 3 * Copyright (c) 1990, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Chris Torek. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #include <stdio.h> 35 #include <string.h> 36 #include <errno.h> 37 #include "local.h" 38 39 static int 40 lflush(FILE *fp) 41 { 42 43 if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR)) 44 return (__sflush(fp)); 45 return (0); 46 } 47 48 size_t 49 fread(void *buf, size_t size, size_t count, FILE *fp) 50 { 51 size_t resid; 52 char *p; 53 int r; 54 size_t total; 55 56 /* 57 * The ANSI standard requires a return value of 0 for a count 58 * or a size of 0. Peculiarily, it imposes no such requirements 59 * on fwrite; it only requires fread to be broken. 60 */ 61 if ((resid = count * size) == 0) 62 return (0); 63 if (fp->_r < 0) 64 fp->_r = 0; 65 total = resid; 66 p = buf; 67 68 #if 1 /* BIONIC: optimize unbuffered reads */ 69 if (fp->_flags & __SNBF && fp->_ur == 0) 70 { 71 /* the following comes mainly from __srefill(), with slight 72 * modifications 73 */ 74 75 /* make sure stdio is set up */ 76 if (!__sdidinit) 77 __sinit(); 78 79 fp->_r = 0; /* largely a convenience for callers */ 80 81 /* SysV does not make this test; take it out for compatibility */ 82 if (fp->_flags & __SEOF) 83 return (EOF); 84 85 /* if not already reading, have to be reading and writing */ 86 if ((fp->_flags & __SRD) == 0) { 87 if ((fp->_flags & __SRW) == 0) { 88 errno = EBADF; 89 fp->_flags |= __SERR; 90 return (EOF); 91 } 92 /* switch to reading */ 93 if (fp->_flags & __SWR) { 94 if (__sflush(fp)) 95 return (EOF); 96 fp->_flags &= ~__SWR; 97 fp->_w = 0; 98 fp->_lbfsize = 0; 99 } 100 fp->_flags |= __SRD; 101 } else { 102 /* 103 * We were reading. If there is an ungetc buffer, 104 * we must have been reading from that. Drop it, 105 * restoring the previous buffer (if any). If there 106 * is anything in that buffer, return. 107 */ 108 if (HASUB(fp)) { 109 FREEUB(fp); 110 } 111 } 112 113 /* 114 * Before reading from a line buffered or unbuffered file, 115 * flush all line buffered output files, per the ANSI C 116 * standard. 117 */ 118 119 if (fp->_flags & (__SLBF|__SNBF)) 120 (void) _fwalk(lflush); 121 122 while (resid > 0) { 123 int len = (*fp->_read)(fp->_cookie, p, resid ); 124 fp->_flags &= ~__SMOD; 125 if (len <= 0) { 126 if (len == 0) 127 fp->_flags |= __SEOF; 128 else { 129 fp->_flags |= __SERR; 130 } 131 return ((total - resid) / size); 132 } 133 p += len; 134 resid -= len; 135 } 136 return (count); 137 } 138 else 139 #endif 140 { 141 while (resid > (size_t)(r = fp->_r)) { 142 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r); 143 fp->_p += r; 144 /* fp->_r = 0 ... done in __srefill */ 145 p += r; 146 resid -= r; 147 if (__srefill(fp)) { 148 /* no more input: return partial result */ 149 return ((total - resid) / size); 150 } 151 } 152 } 153 154 (void)memcpy((void *)p, (void *)fp->_p, resid); 155 fp->_r -= resid; 156 fp->_p += resid; 157 return (count); 158 } 159
