1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "components/rappor/bloom_filter.h"
6
7#include "base/logging.h"
8#include "third_party/smhasher/src/City.h"
9
10namespace rappor {
11
12BloomFilter::BloomFilter(uint32_t bytes_size,
13                         uint32_t hash_function_count,
14                         uint32_t hash_seed_offset)
15    : bytes_(bytes_size),
16      hash_function_count_(hash_function_count),
17      hash_seed_offset_(hash_seed_offset) {
18  DCHECK_GT(bytes_size, 0u);
19}
20
21BloomFilter::~BloomFilter() {}
22
23void BloomFilter::SetString(const std::string& str) {
24  for (size_t i = 0; i < bytes_.size(); ++i) {
25    bytes_[i] = 0;
26  }
27  for (size_t i = 0; i < hash_function_count_; ++i) {
28    // Using CityHash here because we have support for it in Dremel.  Many hash
29    // functions, such as MD5, SHA1, or Murmur, would probably also work.
30    uint32_t index =
31        CityHash64WithSeed(str.data(), str.size(), hash_seed_offset_ + i);
32    // Note that the "bytes" are uint8_t, so they are always 8-bits.
33    uint32_t byte_index = (index / 8) % bytes_.size();
34    uint32_t bit_index = index % 8;
35    bytes_[byte_index] |= 1 << bit_index;
36  }
37}
38
39void BloomFilter::SetBytesForTesting(const ByteVector& bytes) {
40  DCHECK_EQ(bytes_.size(), bytes.size());
41  for (size_t i = 0; i < bytes_.size(); ++i) {
42    bytes_[i] = bytes[i];
43  }
44}
45
46}  // namespace rappor
47