| // Copyright 2019 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "components/optimization_guide/core/bloom_filter.h" |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #include "base/check_op.h" |
| #include "third_party/smhasher/src/MurmurHash3.h" |
| |
| namespace optimization_guide { |
| |
| namespace { |
| |
| uint64_t MurmurHash3(const std::string& str, uint32_t seed) { |
| // Uses MurmurHash3 in coordination with server as it is a fast hashing |
| // function with compatible public client and private server implementations. |
| // DO NOT CHANGE this hashing function without coordination and migration |
| // plan with the server providing the OptimizationGuide proto. |
| uint64_t output[2]; |
| MurmurHash3_x64_128(str.data(), str.size(), seed, &output); |
| // Drop the last 64 bits. |
| return output[0]; |
| } |
| |
| } // namespace |
| |
| BloomFilter::BloomFilter(uint32_t num_hash_functions, uint32_t num_bits) |
| |
| : num_hash_functions_(num_hash_functions), |
| num_bits_(num_bits), |
| bytes_(((num_bits + 7) / 8), 0) { |
| // May be created on one thread but used on another. The first call to |
| // CalledOnValidSequence() will re-bind it. |
| DETACH_FROM_SEQUENCE(sequence_checker_); |
| } |
| |
| BloomFilter::BloomFilter(uint32_t num_hash_functions, |
| uint32_t num_bits, |
| std::string filter_data) |
| |
| : num_hash_functions_(num_hash_functions), |
| num_bits_(num_bits), |
| bytes_(filter_data.size()) { |
| // May be created on one thread but used on another. The first call to |
| // CalledOnValidSequence() will re-bind it. |
| DETACH_FROM_SEQUENCE(sequence_checker_); |
| CHECK_GE(filter_data.size() * 8, num_bits); |
| memcpy(&bytes_[0], filter_data.data(), filter_data.size()); |
| } |
| |
| BloomFilter::~BloomFilter() = default; |
| |
| bool BloomFilter::Contains(const std::string& str) const { |
| DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_); |
| for (size_t i = 0; i < num_hash_functions_; ++i) { |
| uint64_t n = MurmurHash3(str, i) % num_bits_; |
| uint32_t byte_index = (n / 8); |
| uint32_t bit_index = n % 8; |
| if ((bytes_[byte_index] & (1 << bit_index)) == 0) |
| return false; |
| } |
| return true; |
| } |
| |
| void BloomFilter::Add(const std::string& str) { |
| DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_); |
| for (size_t i = 0; i < num_hash_functions_; ++i) { |
| uint64_t n = MurmurHash3(str, i) % num_bits_; |
| uint32_t byte_index = (n / 8); |
| uint32_t bit_index = n % 8; |
| bytes_[byte_index] |= 1 << bit_index; |
| } |
| } |
| |
| } // namespace optimization_guide |