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70 lines
1.6 KiB
C
70 lines
1.6 KiB
C
/*
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* Copyright (C) 2013 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup core_util
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* @{
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*
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* @file
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* @brief Bit arithmetic helper functions implementation
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*
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* @author Kaspar Schleiser <kaspar@schleiser.de>
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* @author Martine Lenders <mlenders@inf.fu-berlin.de>
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*
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* @}
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*/
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#include <stdio.h>
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#include "bitarithm.h"
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unsigned bitarith_msb_32bit_no_native_clz(unsigned v)
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{
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register unsigned r; /* result of log2(v) will go here */
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register unsigned shift;
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/* begin{code-style-ignore} */
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r = (v > 0xFFFF) << 4; v >>= r;
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shift = (v > 0xFF ) << 3; v >>= shift; r |= shift;
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shift = (v > 0xF ) << 2; v >>= shift; r |= shift;
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shift = (v > 0x3 ) << 1; v >>= shift; r |= shift;
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r |= (v >> 1);
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/* end{code-style-ignore} */
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return r;
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}
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unsigned bitarithm_bits_set(unsigned v)
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{
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unsigned c; /* c accumulates the total bits set in v */
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for (c = 0; v; c++) {
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v &= v - 1; /* clear the least significant bit set */
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}
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return c;
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}
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#if !ARCH_32_BIT
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uint8_t bitarithm_bits_set_u32(uint32_t v)
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{
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uint8_t c;
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for (c = 0; v; c++) {
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v &= v - 1; /* clear the least significant bit set */
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}
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return c;
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}
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#endif
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const uint8_t bitarithm_MultiplyDeBruijnBitPosition[32] =
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{
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0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8,
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31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9
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};
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