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// Copyright (c) 2012 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 "chrome/common/metrics/experiments_helper.h"
#include <vector>
#include "base/memory/singleton.h"
#include "base/sha1.h"
#include "base/string16.h"
#include "base/stringprintf.h"
#include "base/sys_byteorder.h"
#include "base/utf_string_conversions.h"
#include "chrome/common/child_process_logging.h"
#include "chrome/common/metrics/variation_ids.h"
namespace {
// The internal singleton accessor for the map, used to keep it thread-safe.
class GroupMapAccessor {
public:
// Retrieve the singleton.
static GroupMapAccessor* GetInstance() {
return Singleton<GroupMapAccessor>::get();
}
GroupMapAccessor() {}
~GroupMapAccessor() {}
// Note that this normally only sets the ID for a group the first time, unless
// |force| is set to true, in which case it will always override it.
void AssociateID(const experiments_helper::SelectedGroupId& group_identifier,
chrome_variations::ID id,
const bool force) {
base::AutoLock scoped_lock(lock_);
if (force ||
group_to_id_map_.find(group_identifier) == group_to_id_map_.end())
group_to_id_map_[group_identifier] = id;
}
chrome_variations::ID GetID(
const experiments_helper::SelectedGroupId& group_identifier) {
base::AutoLock scoped_lock(lock_);
GroupToIDMap::const_iterator it = group_to_id_map_.find(group_identifier);
if (it == group_to_id_map_.end())
return chrome_variations::kEmptyID;
return it->second;
}
private:
typedef std::map<experiments_helper::SelectedGroupId,
chrome_variations::ID,
experiments_helper::SelectedGroupIdCompare> GroupToIDMap;
base::Lock lock_;
GroupToIDMap group_to_id_map_;
};
// Creates unique identifier for the trial by hashing a name string, whether
// it's for the field trial or the group name.
uint32 HashName(const std::string& name) {
// SHA-1 is designed to produce a uniformly random spread in its output space,
// even for nearly-identical inputs.
unsigned char sha1_hash[base::kSHA1Length];
base::SHA1HashBytes(reinterpret_cast<const unsigned char*>(name.c_str()),
name.size(),
sha1_hash);
COMPILE_ASSERT(sizeof(uint32) < sizeof(sha1_hash), need_more_data);
uint32 bits;
memcpy(&bits, sha1_hash, sizeof(bits));
return base::ByteSwapToLE32(bits);
}
experiments_helper::SelectedGroupId MakeSelectedGroupId(
const std::string& trial_name,
const std::string& group_name) {
experiments_helper::SelectedGroupId id;
id.name = HashName(trial_name);
id.group = HashName(group_name);
return id;
}
// Populates |name_group_ids| based on |selected_groups|.
void GetFieldTrialSelectedGroupIdsForSelectedGroups(
const base::FieldTrial::SelectedGroups& selected_groups,
std::vector<experiments_helper::SelectedGroupId>* name_group_ids) {
DCHECK(name_group_ids->empty());
for (base::FieldTrial::SelectedGroups::const_iterator it =
selected_groups.begin(); it != selected_groups.end(); ++it) {
name_group_ids->push_back(MakeSelectedGroupId(it->trial, it->group));
}
}
} // namespace
namespace experiments_helper {
void GetFieldTrialSelectedGroupIds(
std::vector<SelectedGroupId>* name_group_ids) {
DCHECK(name_group_ids->empty());
// A note on thread safety: Since GetFieldTrialSelectedGroups 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 FieldTriaList data.
base::FieldTrial::SelectedGroups selected_groups;
base::FieldTrialList::GetFieldTrialSelectedGroups(&selected_groups);
GetFieldTrialSelectedGroupIdsForSelectedGroups(selected_groups,
name_group_ids);
}
void AssociateGoogleVariationID(const std::string& trial_name,
const std::string& group_name,
chrome_variations::ID id) {
GroupMapAccessor::GetInstance()->AssociateID(
MakeSelectedGroupId(trial_name, group_name), id, false);
}
void AssociateGoogleVariationIDForce(const std::string& trial_name,
const std::string& group_name,
chrome_variations::ID id) {
GroupMapAccessor::GetInstance()->AssociateID(
MakeSelectedGroupId(trial_name, group_name), id, true);
}
chrome_variations::ID GetGoogleVariationID(const std::string& trial_name,
const std::string& group_name) {
return GroupMapAccessor::GetInstance()->GetID(
MakeSelectedGroupId(trial_name, group_name));
}
void SetChildProcessLoggingExperimentList() {
std::vector<SelectedGroupId> name_group_ids;
GetFieldTrialSelectedGroupIds(&name_group_ids);
std::vector<string16> experiment_strings(name_group_ids.size());
for (size_t i = 0; i < name_group_ids.size(); ++i) {
// Wish there was a StringPrintf for string16... :-(
experiment_strings[i] = WideToUTF16(base::StringPrintf(
L"%x-%x", name_group_ids[i].name, name_group_ids[i].group));
}
child_process_logging::SetExperimentList(experiment_strings);
}
} // namespace experiments_helper
// Functions below are exposed for testing explicitly behind this namespace.
// They simply wrap existing functions in this file.
namespace testing {
void TestGetFieldTrialSelectedGroupIdsForSelectedGroups(
const base::FieldTrial::SelectedGroups& selected_groups,
std::vector<experiments_helper::SelectedGroupId>* name_group_ids) {
::GetFieldTrialSelectedGroupIdsForSelectedGroups(selected_groups,
name_group_ids);
}
uint32 TestHashName(const std::string& name) {
return ::HashName(name);
}
} // namespace testing
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