xnu-517.tar.gz

[apple/xnu.git] / bsd / dev / ppc / ffs.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
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 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1991 NeXT Computer, Inc.  All rights reserved.
 *
 *      File:   machdep/i386/libc/ffs.c
 *      Author: Bruce Martin, NeXT Computer, Inc.
 *
 *      This file contains machine dependent code for the ffs function
 *      on NeXT i386-based products.  Currently tuned for the i486.
 *
 * HISTORY
 * 27-Sep-92  Bruce Martin (Bruce_Martin@NeXT.COM)
 *	Created: stolen from Mike's code.
 */

unsigned
ffs(unsigned mask)
{
	unsigned bitpos;

	if (mask == 0)
		return 0;

	bitpos = 1;
	while ((mask & 0xff) == 0) {
		bitpos += 8;
		mask >>= 8;
	}
	while ((mask & 1) == 0) {
		bitpos += 1;
		mask >>= 1;
	}
	return bitpos;
}