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Diffstat (limited to 'third_party/abseil-cpp/absl/flags/internal/registry.h')
| -rw-r--r-- | third_party/abseil-cpp/absl/flags/internal/registry.h | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/flags/internal/registry.h b/third_party/abseil-cpp/absl/flags/internal/registry.h new file mode 100644 index 0000000000..69ff889fb1 --- /dev/null +++ b/third_party/abseil-cpp/absl/flags/internal/registry.h @@ -0,0 +1,124 @@ +// +// 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_ |