mirror of
https://github.com/facebook/rocksdb.git
synced 2024-11-27 02:44:18 +00:00
ef602f6275
Summary: Did some trivial stuffs: * Add more comments; * fix compiler's warning messages (uninitialized variables). * etc Test Plan: make check
73 lines
2 KiB
C++
73 lines
2 KiB
C++
// 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 <atomic>
|
|
#include <memory>
|
|
|
|
namespace rocksdb {
|
|
|
|
class Slice;
|
|
|
|
class DynamicBloom {
|
|
public:
|
|
// total_bits: fixed total bits for the bloom
|
|
// hash_func: customized hash function
|
|
// num_probes: number of hash probes for a single key
|
|
DynamicBloom(uint32_t total_bits,
|
|
uint32_t (*hash_func)(const Slice& key),
|
|
uint32_t num_probes = 6);
|
|
|
|
explicit DynamicBloom(uint32_t total_bits, uint32_t num_probes = 6);
|
|
|
|
// Assuming single threaded access to this function.
|
|
void Add(const Slice& key);
|
|
|
|
// Assuming single threaded access to this function.
|
|
void AddHash(uint32_t hash);
|
|
|
|
// Multithreaded access to this function is OK
|
|
bool MayContain(const Slice& key);
|
|
|
|
// Multithreaded access to this function is OK
|
|
bool MayContainHash(uint32_t hash);
|
|
|
|
private:
|
|
uint32_t (*hash_func_)(const Slice& key);
|
|
const uint32_t kTotalBits;
|
|
const uint32_t kNumProbes;
|
|
std::unique_ptr<unsigned char[]> data_;
|
|
};
|
|
|
|
inline void DynamicBloom::Add(const Slice& key) { AddHash(hash_func_(key)); }
|
|
|
|
inline bool DynamicBloom::MayContain(const Slice& key) {
|
|
return (MayContainHash(hash_func_(key)));
|
|
}
|
|
|
|
inline bool DynamicBloom::MayContainHash(uint32_t h) {
|
|
const uint32_t delta = (h >> 17) | (h << 15); // Rotate right 17 bits
|
|
for (uint32_t i = 0; i < kNumProbes; i++) {
|
|
const uint32_t bitpos = h % kTotalBits;
|
|
if (((data_[bitpos / 8]) & (1 << (bitpos % 8))) == 0) {
|
|
return false;
|
|
}
|
|
h += delta;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
inline void DynamicBloom::AddHash(uint32_t h) {
|
|
const uint32_t delta = (h >> 17) | (h << 15); // Rotate right 17 bits
|
|
for (uint32_t i = 0; i < kNumProbes; i++) {
|
|
const uint32_t bitpos = h % kTotalBits;
|
|
data_[bitpos / 8] |= (1 << (bitpos % 8));
|
|
h += delta;
|
|
}
|
|
}
|
|
|
|
} // rocksdb
|