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fread.c revision 1.4 
      1 /*-
      2  * Copyright (c) 1990 The Regents of the University of California.
      3  * 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 *sccsid = "from: @(#)fread.c	5.4 (Berkeley) 5/4/91";*/
     39 static char *rcsid = "$Id: fread.c,v 1.4 1993/10/04 18:51:10 jtc Exp $";
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <stdio.h>
     43 #include <string.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 	if ((resid = count * size) == 0)
     57 		return (count);
     58 	if (fp->_r < 0)
     59 		fp->_r = 0;
     60 	total = resid;
     61 	p = buf;
     62 	while (resid > (r = fp->_r)) {
     63 		(void) bcopy((void *)fp->_p, (void *)p, (size_t)r);
     64 		fp->_p += r;
     65 		/* fp->_r = 0 ... done in __srefill */
     66 		p += r;
     67 		resid -= r;
     68 		if (__srefill(fp)) {
     69 			/* no more input: return partial result */
     70 			return ((total - resid) / size);
     71 		}
     72 	}
     73 	(void) bcopy((void *)fp->_p, (void *)p, resid);
     74 	fp->_r -= resid;
     75 	fp->_p += resid;
     76 	return (count);
     77 }
     78