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Annotation of kernel/machdep/i386/libc/ffs.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* Copyright (c) 1991 NeXT Computer, Inc.  All rights reserved.
        !            26:  *
        !            27:  *      File:   machdep/i386/libc/ffs.c
        !            28:  *      Author: Bruce Martin, NeXT Computer, Inc.
        !            29:  *
        !            30:  *      This file contains machine dependent code for the ffs function
        !            31:  *      on NeXT i386-based products.  Currently tuned for the i486.
        !            32:  *
        !            33:  * HISTORY
        !            34:  * 27-Sep-92  Bruce Martin ([email protected])
        !            35:  *     Created: stolen from Mike's code.
        !            36:  */
        !            37: 
        !            38: unsigned
        !            39: ffs(unsigned mask)
        !            40: {
        !            41:        unsigned bitpos;
        !            42: 
        !            43:        if (mask == 0)
        !            44:                return 0;
        !            45: 
        !            46:        bitpos = 1;
        !            47:        while ((mask & 0xff) == 0) {
        !            48:                bitpos += 8;
        !            49:                mask >>= 8;
        !            50:        }
        !            51:        while ((mask & 1) == 0) {
        !            52:                bitpos += 1;
        !            53:                mask >>= 1;
        !            54:        }
        !            55:        return bitpos;
        !            56: }

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