104 lines
3.6 KiB
C++
104 lines
3.6 KiB
C++
/*
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* Copyright (c) 2020 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "api/field_trials.h"
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#include <atomic>
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#include <memory>
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#include <string>
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#include <utility>
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#include "absl/strings/string_view.h"
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#include "rtc_base/checks.h"
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#include "rtc_base/containers/flat_map.h"
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#include "system_wrappers/include/field_trial.h"
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namespace {
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webrtc::flat_map<std::string, std::string> InsertIntoMap(absl::string_view s) {
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webrtc::flat_map<std::string, std::string> key_value_map;
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while (!s.empty()) {
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absl::string_view::size_type separator_pos = s.find('/');
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RTC_CHECK_NE(separator_pos, absl::string_view::npos)
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<< "Missing separator '/' after field trial key.";
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RTC_CHECK_GT(separator_pos, 0) << "Field trial key cannot be empty.";
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absl::string_view key = s.substr(0, separator_pos);
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s.remove_prefix(separator_pos + 1);
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RTC_CHECK(!s.empty())
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<< "Missing value after field trial key. String ended.";
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separator_pos = s.find('/');
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RTC_CHECK_NE(separator_pos, absl::string_view::npos)
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<< "Missing terminating '/' in field trial string.";
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RTC_CHECK_GT(separator_pos, 0) << "Field trial value cannot be empty.";
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absl::string_view value = s.substr(0, separator_pos);
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s.remove_prefix(separator_pos + 1);
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// If a key is specified multiple times, only the value linked to the first
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// key is stored. note: This will crash in debug build when calling
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// InitFieldTrialsFromString().
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key_value_map.emplace(key, value);
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}
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return key_value_map;
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}
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// Makes sure that only one instance is created, since the usage
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// of global string makes behaviour unpredicatable otherwise.
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// TODO(bugs.webrtc.org/10335): Remove once global string is gone.
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std::atomic<bool> instance_created_{false};
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} // namespace
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namespace webrtc {
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FieldTrials::FieldTrials(absl::string_view s)
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: uses_global_(true),
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field_trial_string_(s),
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previous_field_trial_string_(webrtc::field_trial::GetFieldTrialString()),
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key_value_map_(InsertIntoMap(s)) {
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// TODO(bugs.webrtc.org/10335): Remove the global string!
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field_trial::InitFieldTrialsFromString(field_trial_string_.c_str());
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RTC_CHECK(!instance_created_.exchange(true))
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<< "Only one instance may be instanciated at any given time!";
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}
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std::unique_ptr<FieldTrials> FieldTrials::CreateNoGlobal(absl::string_view s) {
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return std::unique_ptr<FieldTrials>(new FieldTrials(s, true));
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}
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FieldTrials::FieldTrials(absl::string_view s, bool)
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: uses_global_(false),
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previous_field_trial_string_(nullptr),
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key_value_map_(InsertIntoMap(s)) {}
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FieldTrials::~FieldTrials() {
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// TODO(bugs.webrtc.org/10335): Remove the global string!
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if (uses_global_) {
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field_trial::InitFieldTrialsFromString(previous_field_trial_string_);
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RTC_CHECK(instance_created_.exchange(false));
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}
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}
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std::string FieldTrials::GetValue(absl::string_view key) const {
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auto it = key_value_map_.find(key);
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if (it != key_value_map_.end())
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return it->second;
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// Check the global string so that programs using
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// a mix between FieldTrials and the global string continue to work
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// TODO(bugs.webrtc.org/10335): Remove the global string!
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if (uses_global_) {
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return field_trial::FindFullName(key);
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}
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return "";
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}
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} // namespace webrtc
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