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42 lines
1.2 KiB
C
42 lines
1.2 KiB
C
/*
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Copyright 2011 Jun Wako <wakojun@gmail.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "util.h"
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// bit population - return number of on-bit
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uint8_t bitpop(uint8_t bits)
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{
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uint8_t c;
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for (c = 0; bits; c++)
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bits &= bits -1;
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return c;
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/*
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const uint8_t bit_count[] = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
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return bit_count[bits>>4] + bit_count[bits&0x0F]
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*/
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}
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// most significant on-bit - return highest location of on-bit
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uint8_t biton(uint8_t bits)
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{
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uint8_t n = 0;
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if (bits >> 4) { bits >>= 4; n += 4;}
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if (bits >> 2) { bits >>= 2; n += 2;}
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if (bits >> 1) { bits >>= 1; n += 1;}
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return n;
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}
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