27cf677339
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@16791 a1c6a512-1295-4272-9138-f99709370657
54 lines
1.9 KiB
C
54 lines
1.9 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2008 by Michael Sevakis
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*
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* All files in this archive are subject to the GNU General Public License.
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* See the file COPYING in the source tree root for full license agreement.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "config.h"
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#include <inttypes.h>
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/* find_first_set_bit() - this is a C version of the ffs algorithm devised
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* by D.Seal and posted to comp.sys.arm on 16 Feb 1994.
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*
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* Find the index of the least significant set bit in the word.
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* return values:
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* 0 - bit 0 is set
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* 1 - bit 1 is set
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* ...
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* 31 - bit 31 is set
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* 32 - no bits set
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*/
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/* Table shared with assembly code */
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const uint8_t L_ffs_table[64] ICONST_ATTR =
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{
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/* 0 1 2 3 4 5 6 7 */
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/* ----------------------------------------- */
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32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */
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3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */
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10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */
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0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */
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31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */
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9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */
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30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */
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29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */
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};
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#if !defined(CPU_COLDFIRE)
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int find_first_set_bit(uint32_t val)
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{
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return L_ffs_table[((val & -val)*0x0450fbaf) >> 26];
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}
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#endif
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