fread.c (2978B)
1 /*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Chris Torek. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #if defined(LIBC_SCCS) && !defined(lint) 38 static char rcsid[] = "$OpenBSD: fread.c,v 1.2 1996/08/19 08:32:44 tholo Exp $"; 39 #endif /* LIBC_SCCS and not lint */ 40 41 #include <stdio.h> 42 #include <string.h> 43 #include "local.h" 44 45 size_t 46 fread(buf, size, count, fp) 47 void *buf; 48 size_t size, count; 49 register FILE *fp; 50 { 51 register size_t resid; 52 register char *p; 53 register 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 while (resid > (r = fp->_r)) { 68 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r); 69 fp->_p += r; 70 /* fp->_r = 0 ... done in __srefill */ 71 p += r; 72 resid -= r; 73 if (__srefill(fp)) { 74 /* no more input: return partial result */ 75 return ((total - resid) / size); 76 } 77 } 78 (void)memcpy((void *)p, (void *)fp->_p, resid); 79 fp->_r -= resid; 80 fp->_p += resid; 81 return (count); 82 }