components/variations/active_field_trials.cc

// 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/variations/active_field_trials.h"

#include <stddef.h>

#include <vector>

#include "base/lazy_instance.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "components/variations/hashing.h"
#include "components/variations/synthetic_trials_active_group_id_provider.h"

namespace variations {

namespace {

base::LazyInstance<std::string>::Leaky g_seed_version;

// Populates |name_group_ids| based on |active_groups|. Field trial names are
// suffixed with |suffix| before hashing is executed.
void GetFieldTrialActiveGroupIdsForActiveGroups(
    base::StringPiece suffix,
    const base::FieldTrial::ActiveGroups& active_groups,
    std::vector<ActiveGroupId>* name_group_ids) {
  DCHECK(name_group_ids->empty());
  for (auto it = active_groups.begin(); it != active_groups.end(); ++it) {
    name_group_ids->push_back(
        MakeActiveGroupId(it->trial_name + suffix.as_string(),
                          it->group_name + suffix.as_string()));
  }
}

void AppendActiveGroupIdsAsStrings(
    const std::vector<ActiveGroupId> name_group_ids,
    std::vector<std::string>* output) {
  for (const auto& active_group_id : name_group_ids) {
    output->push_back(base::StringPrintf("%x-%x", active_group_id.name,
                                         active_group_id.group));
  }
}

}  // namespace

ActiveGroupId MakeActiveGroupId(base::StringPiece trial_name,
                                base::StringPiece group_name) {
  ActiveGroupId id;
  id.name = HashName(trial_name);
  id.group = HashName(group_name);
  return id;
}

void GetFieldTrialActiveGroupIds(base::StringPiece suffix,
                                 std::vector<ActiveGroupId>* name_group_ids) {
  DCHECK(name_group_ids->empty());
  // A note on thread safety: Since GetActiveFieldTrialGroups() is thread
  // safe, and we operate on a separate list of that data, this function is
  // technically thread safe as well, with respect to the FieldTrialList data.
  base::FieldTrial::ActiveGroups active_groups;
  base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
  GetFieldTrialActiveGroupIdsForActiveGroups(suffix, active_groups,
                                             name_group_ids);
}

void GetFieldTrialActiveGroupIdsAsStrings(base::StringPiece suffix,
                                          std::vector<std::string>* output) {
  DCHECK(output->empty());
  std::vector<ActiveGroupId> name_group_ids;
  GetFieldTrialActiveGroupIds(suffix, &name_group_ids);
  AppendActiveGroupIdsAsStrings(name_group_ids, output);
}

void GetSyntheticTrialGroupIdsAsString(std::vector<std::string>* output) {
  std::vector<ActiveGroupId> name_group_ids;
  SyntheticTrialsActiveGroupIdProvider::GetInstance()->GetActiveGroupIds(
      &name_group_ids);
  AppendActiveGroupIdsAsStrings(name_group_ids, output);
}

void SetSeedVersion(const std::string& seed_version) {
  g_seed_version.Get() = seed_version;
}

const std::string& GetSeedVersion() {
  return g_seed_version.Get();
}

namespace testing {

void TestGetFieldTrialActiveGroupIds(
    base::StringPiece suffix,
    const base::FieldTrial::ActiveGroups& active_groups,
    std::vector<ActiveGroupId>* name_group_ids) {
  GetFieldTrialActiveGroupIdsForActiveGroups(suffix, active_groups,
                                             name_group_ids);
}

}  // namespace testing

}  // namespace variations