76 lines
1.4 KiB
C
76 lines
1.4 KiB
C
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/**
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* Copyright 2009 Facebook
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* @author Tudor Bosman (tudorb@facebook.com)
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*/
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#ifndef STORAGE_LEVELDB_UTIL_BIT_SET_H_
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#define STORAGE_LEVELDB_UTIL_BIT_SET_H_
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#include <cassert>
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namespace leveldb {
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class BitSet {
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public:
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/**
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* Create a bit set of numBits, with the bits set to either true or false.
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*/
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explicit BitSet(size_t numBits, bool initial=false)
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: numBits_(numBits),
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data_(numWords(), initial ? ~0UL : 0UL) {
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}
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/**
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* Set bit b to 1.
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*/
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void set(size_t b) {
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assert(b >= 0 && b < numBits_);
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data_[word(b)] |= wordOffsetMask(b);
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}
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/**
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* Set bit b to 0;
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*/
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void reset(size_t b) {
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assert(b >= 0 && b < numBits_);
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data_[word(b)] &= ~wordOffsetMask(b);
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}
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/**
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* Get a bit.
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*/
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bool test(int b) const {
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return data_[word(b)] & wordOffsetMask(b);
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}
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/**
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* Return the size of the BitSet, in bits.
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*/
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size_t size() const {
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return numBits_;
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}
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private:
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inline size_t numWords() const {
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if (numBits_ == 0) return 0;
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return 1 + (numBits_-1) / (8*sizeof(unsigned long));
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}
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inline static size_t word(int b) {
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return b / (8*sizeof(unsigned long));
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}
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inline static int wordOffset(int b) {
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return b % (8*sizeof(unsigned long));
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}
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inline static unsigned long wordOffsetMask(int b) {
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return 1UL << wordOffset(b);
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}
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size_t numBits_;
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std::vector<unsigned long> data_;
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};
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} // namespace facebook
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#endif // STORAGE_LEVELDB_UTIL_BIT_SET_H_
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