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rocksdb/util/bit_set.h

72 lines
1.5 KiB

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#pragma once
#include <cassert>
namespace rocksdb {
class BitSet {
public:
/**
* Create a bit set of numBits, with the bits set to either true or false.
*/
explicit BitSet(size_t numBits, bool initial=false)
: numBits_(numBits),
data_(numWords(), initial ? ~0UL : 0UL) {
}
/**
* Set bit b to 1.
*/
void set(size_t b) {
assert(b >= 0 && b < numBits_);
data_[word(b)] |= wordOffsetMask(b);
}
/**
* Set bit b to 0;
*/
void reset(size_t b) {
assert(b >= 0 && b < numBits_);
data_[word(b)] &= ~wordOffsetMask(b);
}
/**
* Get a bit.
*/
bool test(int b) const {
return data_[word(b)] & wordOffsetMask(b);
}
/**
* Return the size of the BitSet, in bits.
*/
size_t size() const {
return numBits_;
}
private:
inline size_t numWords() const {
if (numBits_ == 0) return 0;
return 1 + (numBits_-1) / (8*sizeof(unsigned long));
}
inline static size_t word(int b) {
return b / (8*sizeof(unsigned long));
}
inline static int wordOffset(int b) {
return b % (8*sizeof(unsigned long));
}
inline static unsigned long wordOffsetMask(int b) {
return 1UL << wordOffset(b);
}
size_t numBits_;
std::vector<unsigned long> data_;
};
} // namespace facebook