/*************************************************************************** * __________ __ ___. * Open \______ \ ____ ____ | | _\_ |__ _______ ___ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ * \/ \/ \/ \/ \/ * \$Id\$ * * Copyright (C) 2008 by Michael Sevakis * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * of the License, or (at your option) any later version. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * ****************************************************************************/ #include "config.h" #include /* find_first_set_bit() - this is a C version of the ffs algorithm devised * by D.Seal and posted to comp.sys.arm on 16 Feb 1994. * * Find the index of the least significant set bit in the word. * return values: * 0 - bit 0 is set * 1 - bit 1 is set * ... * 31 - bit 31 is set * 32 - no bits set */ /* Table shared with assembly code */ const uint8_t L_ffs_table[64] ICONST_ATTR = { /* 0 1 2 3 4 5 6 7 */ /* ----------------------------------------- */ 32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */ 3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */ 10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */ 0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */ 31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */ 9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */ 30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */ 29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */ }; #if !defined(CPU_COLDFIRE) int find_first_set_bit(uint32_t val) { return L_ffs_table[((val & -val)*0x0450fbaf) >> 26]; } #endif