xref: /titanic_51/usr/src/lib/libbc/libc/stdio/common/fread.c (revision 5d54f3d8999eac1762fe0a8c7177d20f1f201fae)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 1986 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1984 AT&T */
/*        All Rights Reserved   */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*LINTLIBRARY*/
/*
 * This version reads directly from the buffer rather than looping on getc.
 * Ptr args aren't checked for NULL because the program would be a
 * catastrophic mess anyway.  Better to abort than just to return NULL.
 */
#include <stdio.h>
#include "stdiom.h"
#include <memory.h>

#define MIN(x, y)	(x < y ? x : y)

extern int _filbuf();

int
fread(char *ptr, int size, int count, FILE *iop)
{
	unsigned int nleft;
	int n;

	if (size <= 0 || count <= 0) return 0;
	nleft = count * size;

	/* Put characters in the buffer */
	/* note that the meaning of n when just starting this loop is
	   irrelevant.  It is defined in the loop */
	for ( ; ; ) {
		if (iop->_cnt <= 0) { /* empty buffer */
			if (_filbuf(iop) == EOF)
				return (count - (nleft + size - 1)/size);
			iop->_ptr--;
			iop->_cnt++;
		}
		n = MIN(nleft, iop->_cnt);
		ptr = memcpy(ptr, (char *) iop->_ptr, n) + n;
		iop->_cnt -= n;
		iop->_ptr += n;
		_BUFSYNC(iop);
		if ((nleft -= n) == 0)
			return (count);
	}
}