THUAI6/CAPI/cpp/grpc/include/absl/flags/reflection.h

//
// Copyright 2020 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.
//
// -----------------------------------------------------------------------------
// File: reflection.h
// -----------------------------------------------------------------------------
//
// This file defines the routines to access and operate on an Abseil Flag's
// reflection handle.

#ifndef ABSL_FLAGS_REFLECTION_H_
#define ABSL_FLAGS_REFLECTION_H_

#include <string>

#include "absl/base/config.h"
#include "absl/container/flat_hash_map.h"
#include "absl/flags/commandlineflag.h"
#include "absl/flags/internal/commandlineflag.h"

namespace absl
{
    ABSL_NAMESPACE_BEGIN
    namespace flags_internal
    {
        class FlagSaverImpl;
    }  // namespace flags_internal

    // FindCommandLineFlag()
    //
    // Returns the reflection handle of an Abseil flag of the specified name, or
    // `nullptr` if not found. This function will emit a warning if the name of a
    // 'retired' flag is specified.
    absl::CommandLineFlag* FindCommandLineFlag(absl::string_view name);

    // Returns current state of the Flags registry in a form of mapping from flag
    // name to a flag reflection handle.
    absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags();

    //------------------------------------------------------------------------------
    // FlagSaver
    //------------------------------------------------------------------------------
    //
    // A FlagSaver object stores the state of flags in the scope where the FlagSaver
    // is defined, allowing modification of those flags within that scope and
    // automatic restoration of the flags to their previous state upon leaving the
    // scope.
    //
    // A FlagSaver can be used within tests to temporarily change the test
    // environment and restore the test case to its previous state.
    //
    // Example:
    //
    //   void MyFunc() {
    //    absl::FlagSaver fs;
    //    ...
    //    absl::SetFlag(&FLAGS_myFlag, otherValue);
    //    ...
    //  } // scope of FlagSaver left, flags return to previous state
    //
    // This class is thread-safe.

    class FlagSaver
    {
    public:
        FlagSaver();
        ~FlagSaver();

        FlagSaver(const FlagSaver&) = delete;
        void operator=(const FlagSaver&) = delete;

    private:
        flags_internal::FlagSaverImpl* impl_;
    };

    //-----------------------------------------------------------------------------

    ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_FLAGS_REFLECTION_H_