| // |
| // 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_REGISTRY_H_ |
| #define ABSL_FLAGS_INTERNAL_REGISTRY_H_ |
| |
| #include <functional> |
| #include <map> |
| #include <string> |
| |
| #include "absl/base/config.h" |
| #include "absl/base/macros.h" |
| #include "absl/flags/internal/commandlineflag.h" |
| #include "absl/strings/string_view.h" |
| |
| // -------------------------------------------------------------------- |
| // Global flags registry API. |
| |
| namespace absl { |
| ABSL_NAMESPACE_BEGIN |
| namespace flags_internal { |
| |
| CommandLineFlag* FindCommandLineFlag(absl::string_view name); |
| CommandLineFlag* FindRetiredFlag(absl::string_view name); |
| |
| // Executes specified visitor for each non-retired flag in the registry. |
| // Requires the caller hold the registry lock. |
| void ForEachFlagUnlocked(std::function<void(CommandLineFlag*)> visitor); |
| // Executes specified visitor for each non-retired flag in the registry. While |
| // callback are executed, the registry is locked and can't be changed. |
| void ForEachFlag(std::function<void(CommandLineFlag*)> visitor); |
| |
| //----------------------------------------------------------------------------- |
| |
| bool RegisterCommandLineFlag(CommandLineFlag*); |
| |
| //----------------------------------------------------------------------------- |
| // Retired registrations: |
| // |
| // Retired flag registrations are treated specially. A 'retired' flag is |
| // provided only for compatibility with automated invocations that still |
| // name it. A 'retired' flag: |
| // - is not bound to a C++ FLAGS_ reference. |
| // - has a type and a value, but that value is intentionally inaccessible. |
| // - does not appear in --help messages. |
| // - is fully supported by _all_ flag parsing routines. |
| // - consumes args normally, and complains about type mismatches in its |
| // argument. |
| // - emits a complaint but does not die (e.g. LOG(ERROR)) if it is |
| // accessed by name through the flags API for parsing or otherwise. |
| // |
| // The registrations for a flag happen in an unspecified order as the |
| // initializers for the namespace-scope objects of a program are run. |
| // Any number of weak registrations for a flag can weakly define the flag. |
| // One non-weak registration will upgrade the flag from weak to non-weak. |
| // Further weak registrations of a non-weak flag are ignored. |
| // |
| // This mechanism is designed to support moving dead flags into a |
| // 'graveyard' library. An example migration: |
| // |
| // 0: Remove references to this FLAGS_flagname in the C++ codebase. |
| // 1: Register as 'retired' in old_lib. |
| // 2: Make old_lib depend on graveyard. |
| // 3: Add a redundant 'retired' registration to graveyard. |
| // 4: Remove the old_lib 'retired' registration. |
| // 5: Eventually delete the graveyard registration entirely. |
| // |
| |
| // Retire flag with name "name" and type indicated by ops. |
| bool Retire(const char* name, FlagStaticTypeId type_id); |
| |
| // Registered a retired flag with name 'flag_name' and type 'T'. |
| template <typename T> |
| inline bool RetiredFlag(const char* flag_name) { |
| return flags_internal::Retire(flag_name, &FlagStaticTypeIdGen<T>); |
| } |
| |
| // If the flag is retired, returns true and indicates in |*type_is_bool| |
| // whether the type of the retired flag is a bool. |
| // Only to be called by code that needs to explicitly ignore retired flags. |
| bool IsRetiredFlag(absl::string_view name, bool* type_is_bool); |
| |
| //----------------------------------------------------------------------------- |
| // Saves the states (value, default value, whether the user has set |
| // the flag, registered validators, etc) of all flags, and restores |
| // them when the FlagSaver is destroyed. |
| // |
| // This class is thread-safe. However, its destructor writes to |
| // exactly the set of flags that have changed value during its |
| // lifetime, so concurrent _direct_ access to those flags |
| // (i.e. FLAGS_foo instead of {Get,Set}CommandLineOption()) is unsafe. |
| |
| class FlagSaver { |
| public: |
| FlagSaver(); |
| ~FlagSaver(); |
| |
| FlagSaver(const FlagSaver&) = delete; |
| void operator=(const FlagSaver&) = delete; |
| |
| // Prevents saver from restoring the saved state of flags. |
| void Ignore(); |
| |
| private: |
| class FlagSaverImpl* impl_; // we use pimpl here to keep API steady |
| }; |
| |
| } // namespace flags_internal |
| ABSL_NAMESPACE_END |
| } // namespace absl |
| |
| #endif // ABSL_FLAGS_INTERNAL_REGISTRY_H_ |