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57 lines
1.1 KiB
57 lines
1.1 KiB
/* |
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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 bitarithm.c |
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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 Martin Lenders <mlenders@inf.fu-berlin.de> |
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* @author René Kijewski <rene.kijewski@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 bitarithm_msb(unsigned v) |
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{ |
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if ((signed) v >= 0) { |
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v &= -v; |
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return bitarithm_lsb(v); |
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} |
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else { |
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return sizeof (v) * 8 - 1; |
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} |
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} |
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unsigned bitarithm_lsb(unsigned v) |
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{ |
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unsigned r = 0; |
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while ((v & 1) == 0) { |
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v >>= 1; |
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r++; |
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} |
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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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