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/*
* Copyright (c) 2020 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "api/field_trials.h"
#include <atomic>
#include "rtc_base/checks.h"
#include "system_wrappers/include/field_trial.h"
namespace {
// This part is copied from system_wrappers/field_trial.cc.
webrtc::flat_map<std::string, std::string> InsertIntoMap(const std::string& s) {
std::string::size_type field_start = 0;
webrtc::flat_map<std::string, std::string> key_value_map;
while (field_start < s.size()) {
std::string::size_type separator_pos = s.find('/', field_start);
RTC_CHECK_NE(separator_pos, std::string::npos)
<< "Missing separator '/' after field trial key.";
RTC_CHECK_GT(separator_pos, field_start)
<< "Field trial key cannot be empty.";
std::string key = s.substr(field_start, separator_pos - field_start);
field_start = separator_pos + 1;
RTC_CHECK_LT(field_start, s.size())
<< "Missing value after field trial key. String ended.";
separator_pos = s.find('/', field_start);
RTC_CHECK_NE(separator_pos, std::string::npos)
<< "Missing terminating '/' in field trial string.";
RTC_CHECK_GT(separator_pos, field_start)
<< "Field trial value cannot be empty.";
std::string value = s.substr(field_start, separator_pos - field_start);
field_start = separator_pos + 1;
// If a key is specified multiple times, only the value linked to the first
// key is stored. note: This will crash in debug build when calling
// InitFieldTrialsFromString().
key_value_map.emplace(key, value);
}
// This check is technically redundant due to earlier checks.
// We nevertheless keep the check to make it clear that the entire
// string has been processed, and without indexing past the end.
RTC_CHECK_EQ(field_start, s.size());
return key_value_map;
}
// Makes sure that only one instance is created, since the usage
// of global string makes behaviour unpredicatable otherwise.
// TODO(bugs.webrtc.org/10335): Remove once global string is gone.
std::atomic<bool> instance_created_{false};
} // namespace
namespace webrtc {
FieldTrials::FieldTrials(const std::string& s)
: field_trial_string_(s),
previous_field_trial_string_(webrtc::field_trial::GetFieldTrialString()),
key_value_map_(InsertIntoMap(s)) {
// TODO(bugs.webrtc.org/10335): Remove the global string!
field_trial::InitFieldTrialsFromString(field_trial_string_.c_str());
RTC_CHECK(!instance_created_.exchange(true))
<< "Only one instance may be instanciated at any given time!";
}
FieldTrials::~FieldTrials() {
// TODO(bugs.webrtc.org/10335): Remove the global string!
field_trial::InitFieldTrialsFromString(previous_field_trial_string_);
RTC_CHECK(instance_created_.exchange(false));
}
std::string FieldTrials::Lookup(absl::string_view key) const {
auto it = key_value_map_.find(std::string(key));
if (it != key_value_map_.end())
return it->second;
// Check the global string so that programs using
// a mix between FieldTrials and the global string continue to work
// TODO(bugs.webrtc.org/10335): Remove the global string!
return field_trial::FindFullName(std::string(key));
}
} // namespace webrtc
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