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