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fread.c revision 1.11 
      1 /*	$NetBSD: fread.c,v 1.11 1999/09/16 12:45:34 lukem 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. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 #if 0
     42 static char sccsid[] = "@(#)fread.c	8.2 (Berkeley) 12/11/93";
     43 #else
     44 __RCSID("$NetBSD: fread.c,v 1.11 1999/09/16 12:45:34 lukem Exp $");
     45 #endif
     46 #endif /* LIBC_SCCS and not lint */
     47 
     48 #include <assert.h>
     49 #include <errno.h>
     50 #include <stdio.h>
     51 #include <string.h>
     52 #include "local.h"
     53 #include "reentrant.h"
     54 
     55 size_t
     56 fread(buf, size, count, fp)
     57 	void *buf;
     58 	size_t size, count;
     59 	FILE *fp;
     60 {
     61 	size_t resid;
     62 	char *p;
     63 	int r;
     64 	size_t total;
     65 
     66 	if (size == 0 || count == 0)	/* check first, according to SUS */
     67 		return (0);
     68 	_DIAGASSERT(buf != NULL);
     69 	_DIAGASSERT(fp != NULL);
     70 #ifdef _DIAGNOSTIC
     71 	if (buf == NULL) {
     72 		errno = EFAULT;
     73 		return (0);
     74 	}
     75 	if (fp == NULL) {
     76 		errno = EBADF;
     77 		return (0);
     78 	}
     79 #endif
     80 
     81 	/*
     82 	 * The ANSI standard requires a return value of 0 for a count
     83 	 * or a size of 0.  Peculiarily, it imposes no such requirements
     84 	 * on fwrite; it only requires fread to be broken.
     85 	 */
     86 	if ((resid = count * size) == 0)
     87 		return (0);
     88 	FLOCKFILE(fp);
     89 	if (fp->_r < 0)
     90 		fp->_r = 0;
     91 	total = resid;
     92 	p = buf;
     93 	while (resid > (r = fp->_r)) {
     94 		(void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
     95 		fp->_p += r;
     96 		/* fp->_r = 0 ... done in __srefill */
     97 		p += r;
     98 		resid -= r;
     99 		if (__srefill(fp)) {
    100 			/* no more input: return partial result */
    101 			FUNLOCKFILE(fp);
    102 			return ((total - resid) / size);
    103 		}
    104 	}
    105 	(void)memcpy((void *)p, (void *)fp->_p, resid);
    106 	fp->_r -= resid;
    107 	fp->_p += resid;
    108 	FUNLOCKFILE(fp);
    109 	return (count);
    110 }
    111