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Annotation of XNU/osfmk/kern/bits.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * The contents of this file constitute Original Code as defined in and
        !             7:  * are subject to the Apple Public Source License Version 1.1 (the
        !             8:  * "License").  You may not use this file except in compliance with the
        !             9:  * License.  Please obtain a copy of the License at
        !            10:  * http://www.apple.com/publicsource and read it before using this file.
        !            11:  * 
        !            12:  * This Original Code and all software distributed under the License are
        !            13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            17:  * License for the specific language governing rights and limitations
        !            18:  * under the License.
        !            19:  * 
        !            20:  * @APPLE_LICENSE_HEADER_END@
        !            21:  */
        !            22: /*
        !            23:  * @OSF_COPYRIGHT@
        !            24:  */
        !            25: /*
        !            26:  * HISTORY
        !            27:  * 
        !            28:  * Revision 1.1.1.1  1998/09/22 21:05:35  wsanchez
        !            29:  * Import of Mac OS X kernel (~semeria)
        !            30:  *
        !            31:  * Revision 1.2  1998/04/29 17:35:55  mburg
        !            32:  * MK7.3 merger
        !            33:  *
        !            34:  * Revision 1.1.24.1  1998/02/03  09:27:19  gdt
        !            35:  *     Merge up to MK7.3
        !            36:  *     [1998/02/03  09:12:57  gdt]
        !            37:  *
        !            38:  * Revision 1.1.21.1  1996/11/29  16:57:21  stephen
        !            39:  *     nmklinux_1.0b3_shared into pmk1.1
        !            40:  *     Added explanatory note.
        !            41:  *     [1996/04/10  16:54:46  emcmanus]
        !            42:  * 
        !            43:  * Revision 1.1.22.1  1997/06/17  02:57:05  devrcs
        !            44:  *     Added `testbit()' routine.
        !            45:  *     [1996/03/18  15:21:50  rkc]
        !            46:  * 
        !            47:  * Revision 1.1.7.3  1995/01/10  05:10:36  devrcs
        !            48:  *     mk6 CR801 - copyright marker not FREE_
        !            49:  *     [1994/12/01  19:24:54  dwm]
        !            50:  * 
        !            51:  * Revision 1.1.7.1  1994/06/14  16:59:49  bolinger
        !            52:  *     Merge up to NMK17.2.
        !            53:  *     [1994/06/14  16:53:29  bolinger]
        !            54:  * 
        !            55:  * Revision 1.1.5.1  1994/04/11  09:36:31  bernadat
        !            56:  *     Checked in NMK16_2 revision
        !            57:  *     [94/03/15            bernadat]
        !            58:  * 
        !            59:  * Revision 1.1.3.1  1993/12/23  08:53:13  bernadat
        !            60:  *     Checked in bolinger_860ci revision.
        !            61:  *     [93/11/29            bernadat]
        !            62:  * 
        !            63:  * Revision 1.1.1.2  1993/09/12  15:44:20  bolinger
        !            64:  *     Initial checkin of 860 modifications; MD files from NMK14.8.
        !            65:  * 
        !            66:  * $EndLog$
        !            67:  */
        !            68: /*
        !            69:  * C version of bit manipulation routines now required by kernel.
        !            70:  * Should be replaced with assembler versions in any real port.
        !            71:  *
        !            72:  * Note that these routines use little-endian numbering for bits (i.e.,
        !            73:  * the bit number corresponds to the associated power-of-2).
        !            74:  */
        !            75: #include <mach/machine/vm_param.h>     /* for BYTE_SIZE */
        !            76: 
        !            77: #define INT_SIZE       (BYTE_SIZE * sizeof (int))
        !            78: 
        !            79: /*
        !            80:  * Set indicated bit in bit string.
        !            81:  */
        !            82: void
        !            83: setbit(int bitno, int *s)
        !            84: {
        !            85:        for ( ; INT_SIZE <= bitno; bitno -= INT_SIZE, ++s)
        !            86:                ;
        !            87:        *s |= 1 << bitno;
        !            88: }
        !            89: 
        !            90: /*
        !            91:  * Clear indicated bit in bit string.
        !            92:  */
        !            93: void
        !            94: clrbit(int bitno, int *s)
        !            95: {
        !            96:        for ( ; INT_SIZE <= bitno; bitno -= INT_SIZE, ++s)
        !            97:                ;
        !            98:        *s &= ~(1 << bitno);
        !            99: }
        !           100: 
        !           101: /*
        !           102:  * Find first bit set in bit string.
        !           103:  */
        !           104: int
        !           105: ffsbit(int *s)
        !           106: {
        !           107:        int offset, mask;
        !           108: 
        !           109:        for (offset = 0; !*s; offset += INT_SIZE, ++s)
        !           110:                ;
        !           111:        for (mask = 1; mask; mask <<= 1, ++offset)
        !           112:                if (mask & *s)
        !           113:                        return (offset);
        !           114:        /*
        !           115:         * Shouldn't get here
        !           116:         */
        !           117:        return (0);
        !           118: }
        !           119: 
        !           120: /*
        !           121:  * Test if indicated bit is set in bit string.
        !           122:  */
        !           123: int
        !           124: testbit(int bitno, int *s)
        !           125: {
        !           126:        for ( ; INT_SIZE <= bitno; bitno -= INT_SIZE, ++s)
        !           127:                ;
        !           128:        return(*s & (1 << bitno));
        !           129: }

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