1 /* 2 * Copyright (c) 2022 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 #ifndef API_FIELD_TRIALS_H_ 12 #define API_FIELD_TRIALS_H_ 13 14 #include <memory> 15 #include <string> 16 17 #include "absl/strings/string_view.h" 18 #include "api/field_trials_registry.h" 19 #include "rtc_base/containers/flat_map.h" 20 21 namespace webrtc { 22 23 // The FieldTrials class is used to inject field trials into webrtc. 24 // 25 // Field trials allow webrtc clients (such as Chromium) to turn on feature code 26 // in binaries out in the field and gather information with that. 27 // 28 // They are designed to be easy to use with Chromium field trials and to speed 29 // up developers by reducing the need to wire up APIs to control whether a 30 // feature is on/off. 31 // 32 // The field trials are injected into objects that use them at creation time. 33 // 34 // NOTE: Creating multiple FieldTrials-object is currently prohibited 35 // until we remove the global string (TODO(bugs.webrtc.org/10335)) 36 // (unless using CreateNoGlobal): 37 class FieldTrials : public FieldTrialsRegistry { 38 public: 39 explicit FieldTrials(const std::string& s); 40 ~FieldTrials(); 41 42 // Create a FieldTrials object that is not reading/writing from 43 // global variable (i.e can not be used for all parts of webrtc). 44 static std::unique_ptr<FieldTrials> CreateNoGlobal(const std::string& s); 45 46 private: 47 explicit FieldTrials(const std::string& s, bool); 48 49 std::string GetValue(absl::string_view key) const override; 50 51 const bool uses_global_; 52 const std::string field_trial_string_; 53 const char* const previous_field_trial_string_; 54 const flat_map<std::string, std::string> key_value_map_; 55 }; 56 57 } // namespace webrtc 58 59 #endif // API_FIELD_TRIALS_H_ 60