292 lines
9.8 KiB
C++
292 lines
9.8 KiB
C++
/*
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* Copyright 2018 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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#ifndef RTC_BASE_EXPERIMENTS_FIELD_TRIAL_PARSER_H_
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#define RTC_BASE_EXPERIMENTS_FIELD_TRIAL_PARSER_H_
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#include <stdint.h>
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#include <initializer_list>
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#include <map>
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#include <set>
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#include <string>
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#include <vector>
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#include "absl/strings/string_view.h"
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#include "absl/types/optional.h"
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// Field trial parser functionality. Provides funcitonality to parse field trial
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// argument strings in key:value format. Each parameter is described using
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// key:value, parameters are separated with a ,. Values can't include the comma
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// character, since there's no quote facility. For most types, white space is
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// ignored. Parameters are declared with a given type for which an
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// implementation of ParseTypedParameter should be provided. The
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// ParseTypedParameter implementation is given whatever is between the : and the
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// ,. If the key is provided without : a FieldTrialOptional will use nullopt.
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// Example string: "my_optional,my_int:3,my_string:hello"
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// For further description of usage and behavior, see the examples in the unit
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// tests.
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namespace webrtc {
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class FieldTrialParameterInterface {
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public:
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virtual ~FieldTrialParameterInterface();
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std::string key() const { return key_; }
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protected:
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// Protected to allow implementations to provide assignment and copy.
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FieldTrialParameterInterface(const FieldTrialParameterInterface&) = default;
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FieldTrialParameterInterface& operator=(const FieldTrialParameterInterface&) =
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default;
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explicit FieldTrialParameterInterface(absl::string_view key);
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friend void ParseFieldTrial(
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std::initializer_list<FieldTrialParameterInterface*> fields,
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absl::string_view trial_string);
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void MarkAsUsed() { used_ = true; }
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virtual bool Parse(absl::optional<std::string> str_value) = 0;
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virtual void ParseDone() {}
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std::vector<FieldTrialParameterInterface*> sub_parameters_;
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private:
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std::string key_;
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bool used_ = false;
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};
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// ParseFieldTrial function parses the given string and fills the given fields
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// with extracted values if available.
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void ParseFieldTrial(
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std::initializer_list<FieldTrialParameterInterface*> fields,
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absl::string_view trial_string);
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// Specialize this in code file for custom types. Should return absl::nullopt if
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// the given string cannot be properly parsed.
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template <typename T>
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absl::optional<T> ParseTypedParameter(absl::string_view);
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// This class uses the ParseTypedParameter function to implement a parameter
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// implementation with an enforced default value.
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template <typename T>
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class FieldTrialParameter : public FieldTrialParameterInterface {
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public:
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FieldTrialParameter(absl::string_view key, T default_value)
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: FieldTrialParameterInterface(key), value_(default_value) {}
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T Get() const { return value_; }
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operator T() const { return Get(); }
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const T* operator->() const { return &value_; }
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void SetForTest(T value) { value_ = value; }
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protected:
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bool Parse(absl::optional<std::string> str_value) override {
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if (str_value) {
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absl::optional<T> value = ParseTypedParameter<T>(*str_value);
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if (value.has_value()) {
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value_ = value.value();
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return true;
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}
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}
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return false;
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}
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private:
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T value_;
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};
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// This class uses the ParseTypedParameter function to implement a parameter
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// implementation with an enforced default value and a range constraint. Values
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// outside the configured range will be ignored.
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template <typename T>
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class FieldTrialConstrained : public FieldTrialParameterInterface {
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public:
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FieldTrialConstrained(absl::string_view key,
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T default_value,
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absl::optional<T> lower_limit,
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absl::optional<T> upper_limit)
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: FieldTrialParameterInterface(key),
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value_(default_value),
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lower_limit_(lower_limit),
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upper_limit_(upper_limit) {}
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T Get() const { return value_; }
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operator T() const { return Get(); }
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const T* operator->() const { return &value_; }
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protected:
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bool Parse(absl::optional<std::string> str_value) override {
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if (str_value) {
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absl::optional<T> value = ParseTypedParameter<T>(*str_value);
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if (value && (!lower_limit_ || *value >= *lower_limit_) &&
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(!upper_limit_ || *value <= *upper_limit_)) {
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value_ = *value;
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return true;
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}
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}
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return false;
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}
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private:
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T value_;
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absl::optional<T> lower_limit_;
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absl::optional<T> upper_limit_;
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};
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class AbstractFieldTrialEnum : public FieldTrialParameterInterface {
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public:
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AbstractFieldTrialEnum(absl::string_view key,
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int default_value,
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std::map<std::string, int> mapping);
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~AbstractFieldTrialEnum() override;
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AbstractFieldTrialEnum(const AbstractFieldTrialEnum&);
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protected:
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bool Parse(absl::optional<std::string> str_value) override;
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protected:
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int value_;
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std::map<std::string, int> enum_mapping_;
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std::set<int> valid_values_;
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};
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// The FieldTrialEnum class can be used to quickly define a parser for a
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// specific enum. It handles values provided as integers and as strings if a
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// mapping is provided.
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template <typename T>
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class FieldTrialEnum : public AbstractFieldTrialEnum {
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public:
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FieldTrialEnum(absl::string_view key,
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T default_value,
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std::map<std::string, T> mapping)
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: AbstractFieldTrialEnum(key,
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static_cast<int>(default_value),
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ToIntMap(mapping)) {}
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T Get() const { return static_cast<T>(value_); }
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operator T() const { return Get(); }
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private:
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static std::map<std::string, int> ToIntMap(std::map<std::string, T> mapping) {
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std::map<std::string, int> res;
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for (const auto& it : mapping)
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res[it.first] = static_cast<int>(it.second);
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return res;
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}
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};
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// This class uses the ParseTypedParameter function to implement an optional
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// parameter implementation that can default to absl::nullopt.
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template <typename T>
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class FieldTrialOptional : public FieldTrialParameterInterface {
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public:
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explicit FieldTrialOptional(absl::string_view key)
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: FieldTrialParameterInterface(key) {}
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FieldTrialOptional(absl::string_view key, absl::optional<T> default_value)
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: FieldTrialParameterInterface(key), value_(default_value) {}
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absl::optional<T> GetOptional() const { return value_; }
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const T& Value() const { return value_.value(); }
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const T& operator*() const { return value_.value(); }
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const T* operator->() const { return &value_.value(); }
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explicit operator bool() const { return value_.has_value(); }
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protected:
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bool Parse(absl::optional<std::string> str_value) override {
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if (str_value) {
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absl::optional<T> value = ParseTypedParameter<T>(*str_value);
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if (!value.has_value())
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return false;
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value_ = value.value();
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} else {
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value_ = absl::nullopt;
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}
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return true;
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}
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private:
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absl::optional<T> value_;
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};
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// Equivalent to a FieldTrialParameter<bool> in the case that both key and value
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// are present. If key is missing, evaluates to false. If key is present, but no
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// explicit value is provided, the flag evaluates to true.
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class FieldTrialFlag : public FieldTrialParameterInterface {
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public:
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explicit FieldTrialFlag(absl::string_view key);
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FieldTrialFlag(absl::string_view key, bool default_value);
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bool Get() const;
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explicit operator bool() const;
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protected:
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bool Parse(absl::optional<std::string> str_value) override;
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private:
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bool value_;
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};
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template <typename T>
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absl::optional<absl::optional<T>> ParseOptionalParameter(
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absl::string_view str) {
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if (str.empty())
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return absl::optional<T>();
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auto parsed = ParseTypedParameter<T>(str);
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if (parsed.has_value())
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return parsed;
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return absl::nullopt;
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}
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template <>
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absl::optional<bool> ParseTypedParameter<bool>(absl::string_view str);
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template <>
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absl::optional<double> ParseTypedParameter<double>(absl::string_view str);
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template <>
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absl::optional<int> ParseTypedParameter<int>(absl::string_view str);
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template <>
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absl::optional<unsigned> ParseTypedParameter<unsigned>(absl::string_view str);
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template <>
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absl::optional<std::string> ParseTypedParameter<std::string>(
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absl::string_view str);
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template <>
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absl::optional<absl::optional<bool>> ParseTypedParameter<absl::optional<bool>>(
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absl::string_view str);
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template <>
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absl::optional<absl::optional<int>> ParseTypedParameter<absl::optional<int>>(
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absl::string_view str);
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template <>
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absl::optional<absl::optional<unsigned>>
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ParseTypedParameter<absl::optional<unsigned>>(absl::string_view str);
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template <>
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absl::optional<absl::optional<double>>
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ParseTypedParameter<absl::optional<double>>(absl::string_view str);
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// Accepts true, false, else parsed with sscanf %i, true if != 0.
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extern template class FieldTrialParameter<bool>;
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// Interpreted using sscanf %lf.
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extern template class FieldTrialParameter<double>;
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// Interpreted using sscanf %i.
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extern template class FieldTrialParameter<int>;
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// Interpreted using sscanf %u.
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extern template class FieldTrialParameter<unsigned>;
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// Using the given value as is.
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extern template class FieldTrialParameter<std::string>;
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extern template class FieldTrialConstrained<double>;
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extern template class FieldTrialConstrained<int>;
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extern template class FieldTrialConstrained<unsigned>;
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extern template class FieldTrialOptional<double>;
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extern template class FieldTrialOptional<int>;
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extern template class FieldTrialOptional<unsigned>;
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extern template class FieldTrialOptional<bool>;
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extern template class FieldTrialOptional<std::string>;
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} // namespace webrtc
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#endif // RTC_BASE_EXPERIMENTS_FIELD_TRIAL_PARSER_H_
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