veclavtlica
31 lines
535 B
C
31 lines
535 B
C
#ifndef COM_BITS_H
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#define COM_BITS_H
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#include "def.h"
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#include <assert.h>
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#include <stdint.h>
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/* How many bits needed to represent a given number */
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/* Alternitive semntic: nearest upper power of two */
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static inline int com_bits_needed(uint32_t v) {
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#ifdef COM_DEF_COMPILE_MODERN
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/* Use intrinsic, required for fast sqrt impl */
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return v == 0 ? 1 : 32 - __builtin_clz(v);
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#else
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#endif
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if (v == 0)
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return 1;
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v--;
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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v++;
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return v;
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}
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#endif
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