| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "components/rappor/rappor_metric.h" |
| |
| #include "base/logging.h" |
| #include "base/rand_util.h" |
| #include "components/rappor/public/rappor_parameters.h" |
| #include "components/rappor/reports.h" |
| |
| namespace rappor { |
| |
| RapporMetric::RapporMetric(const std::string& metric_name, |
| const RapporParameters& parameters, |
| int32_t cohort_seed) |
| : metric_name_(metric_name), |
| parameters_(parameters), |
| sample_count_(0), |
| bloom_filter_(parameters.bloom_filter_size_bytes, |
| parameters.bloom_filter_hash_function_count, |
| (cohort_seed % parameters.num_cohorts) * |
| parameters.bloom_filter_hash_function_count) { |
| DCHECK_GE(cohort_seed, 0); |
| DCHECK_LT(cohort_seed, RapporParameters::kMaxCohorts); |
| // Since cohort_seed is in the range [0, kMaxCohorts), num_cohorts should |
| // divide kMaxCohorts for each cohort to have equal weight. |
| DCHECK_EQ(0, RapporParameters::kMaxCohorts % parameters.num_cohorts); |
| } |
| |
| RapporMetric::~RapporMetric() {} |
| |
| void RapporMetric::AddSample(const std::string& str) { |
| ++sample_count_; |
| // Replace the previous sample with a 1 in sample_count_ chance so that each |
| // sample has equal probability of being reported. |
| if (base::RandGenerator(sample_count_) == 0) { |
| bloom_filter_.SetString(str); |
| } |
| } |
| |
| ByteVector RapporMetric::GetReport(const std::string& secret) const { |
| return internal::GenerateReport( |
| secret, |
| internal::kNoiseParametersForLevel[parameters().noise_level], |
| bytes()); |
| } |
| |
| } // namespace rappor |
