Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2020 The WebRTC project authors. All Rights Reserved. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license |
| 5 | * that can be found in the LICENSE file in the root of the source |
| 6 | * tree. An additional intellectual property rights grant can be found |
| 7 | * in the file PATENTS. All contributing project authors may |
| 8 | * be found in the AUTHORS file in the root of the source tree. |
| 9 | */ |
| 10 | |
| 11 | #include "api/field_trials.h" |
| 12 | |
| 13 | #include <atomic> |
| 14 | |
| 15 | #include "rtc_base/checks.h" |
| 16 | #include "system_wrappers/include/field_trial.h" |
| 17 | |
| 18 | namespace { |
| 19 | |
| 20 | // This part is copied from system_wrappers/field_trial.cc. |
| 21 | webrtc::flat_map<std::string, std::string> InsertIntoMap(const std::string& s) { |
| 22 | std::string::size_type field_start = 0; |
| 23 | webrtc::flat_map<std::string, std::string> key_value_map; |
| 24 | while (field_start < s.size()) { |
| 25 | std::string::size_type separator_pos = s.find('/', field_start); |
| 26 | RTC_CHECK_NE(separator_pos, std::string::npos) |
| 27 | << "Missing separator '/' after field trial key."; |
| 28 | RTC_CHECK_GT(separator_pos, field_start) |
| 29 | << "Field trial key cannot be empty."; |
| 30 | std::string key = s.substr(field_start, separator_pos - field_start); |
| 31 | field_start = separator_pos + 1; |
| 32 | |
| 33 | RTC_CHECK_LT(field_start, s.size()) |
| 34 | << "Missing value after field trial key. String ended."; |
| 35 | separator_pos = s.find('/', field_start); |
| 36 | RTC_CHECK_NE(separator_pos, std::string::npos) |
| 37 | << "Missing terminating '/' in field trial string."; |
| 38 | RTC_CHECK_GT(separator_pos, field_start) |
| 39 | << "Field trial value cannot be empty."; |
| 40 | std::string value = s.substr(field_start, separator_pos - field_start); |
| 41 | field_start = separator_pos + 1; |
| 42 | |
| 43 | // If a key is specified multiple times, only the value linked to the first |
| 44 | // key is stored. note: This will crash in debug build when calling |
| 45 | // InitFieldTrialsFromString(). |
| 46 | key_value_map.emplace(key, value); |
| 47 | } |
| 48 | // This check is technically redundant due to earlier checks. |
| 49 | // We nevertheless keep the check to make it clear that the entire |
| 50 | // string has been processed, and without indexing past the end. |
| 51 | RTC_CHECK_EQ(field_start, s.size()); |
| 52 | |
| 53 | return key_value_map; |
| 54 | } |
| 55 | |
| 56 | // Makes sure that only one instance is created, since the usage |
| 57 | // of global string makes behaviour unpredicatable otherwise. |
| 58 | // TODO(bugs.webrtc.org/10335): Remove once global string is gone. |
| 59 | std::atomic<bool> instance_created_{false}; |
| 60 | |
| 61 | } // namespace |
| 62 | |
| 63 | namespace webrtc { |
| 64 | |
| 65 | FieldTrials::FieldTrials(const std::string& s) |
Jonas Oreland | f096e74 | 2022-05-31 09:15:19 | [diff] [blame] | 66 | : uses_global_(true), |
| 67 | field_trial_string_(s), |
Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 68 | previous_field_trial_string_(webrtc::field_trial::GetFieldTrialString()), |
| 69 | key_value_map_(InsertIntoMap(s)) { |
| 70 | // TODO(bugs.webrtc.org/10335): Remove the global string! |
| 71 | field_trial::InitFieldTrialsFromString(field_trial_string_.c_str()); |
| 72 | RTC_CHECK(!instance_created_.exchange(true)) |
| 73 | << "Only one instance may be instanciated at any given time!"; |
| 74 | } |
| 75 | |
Jonas Oreland | f096e74 | 2022-05-31 09:15:19 | [diff] [blame] | 76 | std::unique_ptr<FieldTrials> FieldTrials::CreateNoGlobal(const std::string& s) { |
| 77 | return std::unique_ptr<FieldTrials>(new FieldTrials(s, true)); |
| 78 | } |
| 79 | |
| 80 | FieldTrials::FieldTrials(const std::string& s, bool) |
| 81 | : uses_global_(false), |
| 82 | previous_field_trial_string_(nullptr), |
| 83 | key_value_map_(InsertIntoMap(s)) {} |
| 84 | |
Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 85 | FieldTrials::~FieldTrials() { |
| 86 | // TODO(bugs.webrtc.org/10335): Remove the global string! |
Jonas Oreland | f096e74 | 2022-05-31 09:15:19 | [diff] [blame] | 87 | if (uses_global_) { |
| 88 | field_trial::InitFieldTrialsFromString(previous_field_trial_string_); |
| 89 | RTC_CHECK(instance_created_.exchange(false)); |
| 90 | } |
Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 91 | } |
| 92 | |
Emil Lundmark | 1c8103d | 2022-09-21 13:20:22 | [diff] [blame] | 93 | std::string FieldTrials::GetValue(absl::string_view key) const { |
Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 94 | auto it = key_value_map_.find(std::string(key)); |
| 95 | if (it != key_value_map_.end()) |
| 96 | return it->second; |
| 97 | |
| 98 | // Check the global string so that programs using |
| 99 | // a mix between FieldTrials and the global string continue to work |
| 100 | // TODO(bugs.webrtc.org/10335): Remove the global string! |
Jonas Oreland | f096e74 | 2022-05-31 09:15:19 | [diff] [blame] | 101 | if (uses_global_) { |
| 102 | return field_trial::FindFullName(std::string(key)); |
| 103 | } |
| 104 | return ""; |
Jonas Oreland | 128c4dc | 2022-03-30 05:57:48 | [diff] [blame] | 105 | } |
| 106 | |
| 107 | } // namespace webrtc |