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Annotation of kernel/machdep/i386/libc/ffs.c, revision 1.1.1.1

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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