af02b83b88
Basic bitmap is obvious. Hierarchical bitmap is structure of several bitmaps, where higher levels are conjunctions of intervals on level below, allowing for efficient lookup of first unset bit.
38 lines
909 B
C
38 lines
909 B
C
/*
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* BIRD Library -- Generic Bit Operations
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*
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* (c) 1998 Martin Mares <mj@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#ifndef _BIRD_BITOPTS_H_
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#define _BIRD_BITOPTS_H_
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#include "sysdep/config.h"
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/*
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* Bit mask operations:
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*
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* u32_mkmask Make bit mask consisting of <n> consecutive ones
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* from the left and the rest filled with zeroes.
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* E.g., u32_mkmask(5) = 0xf8000000.
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* u32_masklen Inverse operation to u32_mkmask, -1 if not a bitmask.
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*/
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u32 u32_mkmask(uint n);
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uint u32_masklen(u32 x);
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u32 u32_log2(u32 v);
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static inline u32 u32_hash(u32 v) { return v * 2902958171u; }
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static inline u8 u32_popcount(u32 v) { return __builtin_popcount(v); }
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static inline int u32_clz(u32 v) { return __builtin_clz(v); }
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static inline int u32_ctz(u32 v) { return __builtin_ctz(v); }
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static inline int uint_is_pow2(uint n) { return n && !(n & (n-1)); }
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#endif
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