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Diffstat (limited to 'third_party/abseil-cpp/absl/flags/internal/commandlineflag.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/flags/internal/commandlineflag.h | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/flags/internal/commandlineflag.h b/third_party/abseil-cpp/absl/flags/internal/commandlineflag.h new file mode 100644 index 0000000000..6363c6615b --- /dev/null +++ b/third_party/abseil-cpp/absl/flags/internal/commandlineflag.h @@ -0,0 +1,213 @@ +// +// Copyright 2019 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_ +#define ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_ + +#include <stddef.h> +#include <stdint.h> + +#include <memory> +#include <string> +#include <typeinfo> + +#include "absl/base/config.h" +#include "absl/base/macros.h" +#include "absl/flags/config.h" +#include "absl/flags/marshalling.h" +#include "absl/strings/string_view.h" +#include "absl/types/optional.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace flags_internal { + +// An alias for flag static type id. Values of type identify the flag value type +// simialarly to typeid(T), but without relying on RTTI being available. In most +// cases this id is enough to uniquely identify the flag's value type. In a few +// cases we'll have to resort to using actual RTTI implementation if it is +// available. +using FlagStaticTypeId = void* (*)(); + +// Address of this function template is used in current implementation as a flag +// static type id. +template <typename T> +void* FlagStaticTypeIdGen() { +#if defined(ABSL_FLAGS_INTERNAL_HAS_RTTI) + return const_cast<std::type_info*>(&typeid(T)); +#else + return nullptr; +#endif +} + +// Options that control SetCommandLineOptionWithMode. +enum FlagSettingMode { + // update the flag's value unconditionally (can call this multiple times). + SET_FLAGS_VALUE, + // update the flag's value, but *only if* it has not yet been updated + // with SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef". + SET_FLAG_IF_DEFAULT, + // set the flag's default value to this. If the flag has not been updated + // yet (via SET_FLAGS_VALUE, SET_FLAG_IF_DEFAULT, or "FLAGS_xxx = nondef") + // change the flag's current value to the new default value as well. + SET_FLAGS_DEFAULT +}; + +// Options that control SetFromString: Source of a value. +enum ValueSource { + // Flag is being set by value specified on a command line. + kCommandLine, + // Flag is being set by value specified in the code. + kProgrammaticChange, +}; + +// Handle to FlagState objects. Specific flag state objects will restore state +// of a flag produced this flag state from method CommandLineFlag::SaveState(). +class FlagStateInterface { + public: + virtual ~FlagStateInterface() {} + + // Restores the flag originated this object to the saved state. + virtual void Restore() const = 0; +}; + +// Holds all information for a flag. +class CommandLineFlag { + public: + constexpr CommandLineFlag() = default; + + // Not copyable/assignable. + CommandLineFlag(const CommandLineFlag&) = delete; + CommandLineFlag& operator=(const CommandLineFlag&) = delete; + + // Non-polymorphic access methods. + + // Return true iff flag has type T. + template <typename T> + inline bool IsOfType() const { + return TypeId() == &flags_internal::FlagStaticTypeIdGen<T>; + } + + // Attempts to retrieve the flag value. Returns value on success, + // absl::nullopt otherwise. + template <typename T> + absl::optional<T> Get() const { + if (IsRetired() || !IsOfType<T>()) { + return absl::nullopt; + } + + // Implementation notes: + // + // We are wrapping a union around the value of `T` to serve three purposes: + // + // 1. `U.value` has correct size and alignment for a value of type `T` + // 2. The `U.value` constructor is not invoked since U's constructor does + // not do it explicitly. + // 3. The `U.value` destructor is invoked since U's destructor does it + // explicitly. This makes `U` a kind of RAII wrapper around non default + // constructible value of T, which is destructed when we leave the + // scope. We do need to destroy U.value, which is constructed by + // CommandLineFlag::Read even though we left it in a moved-from state + // after std::move. + // + // All of this serves to avoid requiring `T` being default constructible. + union U { + T value; + U() {} + ~U() { value.~T(); } + }; + U u; + + Read(&u.value); + return std::move(u.value); + } + + // Polymorphic access methods + + // Returns name of this flag. + virtual absl::string_view Name() const = 0; + // Returns name of the file where this flag is defined. + virtual std::string Filename() const = 0; + // Returns name of the flag's value type for some built-in types or empty + // std::string. + virtual absl::string_view Typename() const = 0; + // Returns help message associated with this flag. + virtual std::string Help() const = 0; + // Returns true iff this object corresponds to retired flag. + virtual bool IsRetired() const { return false; } + // Returns true iff this is a handle to an Abseil Flag. + virtual bool IsAbseilFlag() const { return true; } + // Returns id of the flag's value type. + virtual FlagStaticTypeId TypeId() const = 0; + virtual bool IsModified() const = 0; + virtual bool IsSpecifiedOnCommandLine() const = 0; + virtual std::string DefaultValue() const = 0; + virtual std::string CurrentValue() const = 0; + + // Interfaces to operate on validators. + virtual bool ValidateInputValue(absl::string_view value) const = 0; + + // Interface to save flag to some persistent state. Returns current flag state + // or nullptr if flag does not support saving and restoring a state. + virtual std::unique_ptr<FlagStateInterface> SaveState() = 0; + + // Sets the value of the flag based on specified std::string `value`. If the flag + // was successfully set to new value, it returns true. Otherwise, sets `error` + // to indicate the error, leaves the flag unchanged, and returns false. There + // are three ways to set the flag's value: + // * Update the current flag value + // * Update the flag's default value + // * Update the current flag value if it was never set before + // The mode is selected based on `set_mode` parameter. + virtual bool SetFromString(absl::string_view value, + flags_internal::FlagSettingMode set_mode, + flags_internal::ValueSource source, + std::string* error) = 0; + + // Checks that flags default value can be converted to std::string and back to the + // flag's value type. + virtual void CheckDefaultValueParsingRoundtrip() const = 0; + + protected: + ~CommandLineFlag() = default; + + private: + // Copy-construct a new value of the flag's type in a memory referenced by + // the dst based on the current flag's value. + virtual void Read(void* dst) const = 0; +}; + +// This macro is the "source of truth" for the list of supported flag built-in +// types. +#define ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(A) \ + A(bool) \ + A(short) \ + A(unsigned short) \ + A(int) \ + A(unsigned int) \ + A(long) \ + A(unsigned long) \ + A(long long) \ + A(unsigned long long) \ + A(double) \ + A(float) \ + A(std::string) \ + A(std::vector<std::string>) + +} // namespace flags_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_ |