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Diffstat (limited to 'absl/flags/internal/registry.h')
| -rw-r--r-- | absl/flags/internal/registry.h | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h new file mode 100644 index 000000000000..bd141e1e23d2 --- /dev/null +++ b/absl/flags/internal/registry.h @@ -0,0 +1,168 @@ +// +// 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/macros.h" +#include "absl/flags/internal/commandlineflag.h" + +// -------------------------------------------------------------------- +// Global flags registry API. + +namespace absl { +namespace flags_internal { + +// CommandLineFlagInfo holds all information for a flag. +struct CommandLineFlagInfo { + std::string name; // the name of the flag + std::string type; // DO NOT use. Use flag->IsOfType<T>() instead. + std::string description; // the "help text" associated with the flag + std::string current_value; // the current value, as a std::string + std::string default_value; // the default value, as a std::string + std::string filename; // 'cleaned' version of filename holding the flag + bool has_validator_fn; // true if RegisterFlagValidator called on this flag + + bool is_default; // true if the flag has the default value and + // has not been set explicitly from the cmdline + // or via SetCommandLineOption. + + // nullptr for ABSL_FLAG. A pointer to the flag's current value + // otherwise. E.g., for DEFINE_int32(foo, ...), flag_ptr will be + // &FLAGS_foo. + const void* flag_ptr; +}; + +//----------------------------------------------------------------------------- + +void FillCommandLineFlagInfo(CommandLineFlag* flag, + CommandLineFlagInfo* result); + +//----------------------------------------------------------------------------- + +CommandLineFlag* FindCommandLineFlag(absl::string_view name); +CommandLineFlag* FindCommandLineV1Flag(const void* flag_ptr); +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); + +//----------------------------------------------------------------------------- + +// Store the list of all flags in *OUTPUT, sorted by file. +void GetAllFlags(std::vector<CommandLineFlagInfo>* OUTPUT); + +//----------------------------------------------------------------------------- + +bool RegisterCommandLineFlag(CommandLineFlag*, const void* ptr = nullptr); + +//----------------------------------------------------------------------------- +// 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. +// +// Returns bool to enable use in namespace-scope initializers. +// For example: +// +// static const bool dummy = base::RetiredFlag<int32_t>("myflag"); +// +// Or to declare several at once: +// +// static bool dummies[] = { +// base::RetiredFlag<std::string>("some_string_flag"), +// base::RetiredFlag<double>("some_double_flag"), +// base::RetiredFlag<int32_t>("some_int32_flag") +// }; + +// Retire flag with name "name" and type indicated by ops. +bool Retire(FlagOpFn ops, FlagMarshallingOpFn marshalling_ops, + const char* name); + +// 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(flags_internal::FlagOps<T>, + flags_internal::FlagMarshallingOps<T>, + flag_name); +} + +// 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 +} // namespace absl + +#endif // ABSL_FLAGS_INTERNAL_REGISTRY_H_ |