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Diffstat (limited to 'third_party/abseil_cpp/absl/flags/internal/flag.h')
| -rw-r--r-- | third_party/abseil_cpp/absl/flags/internal/flag.h | 775 |
1 files changed, 0 insertions, 775 deletions
diff --git a/third_party/abseil_cpp/absl/flags/internal/flag.h b/third_party/abseil_cpp/absl/flags/internal/flag.h deleted file mode 100644 index 370d8a02ef04..000000000000 --- a/third_party/abseil_cpp/absl/flags/internal/flag.h +++ /dev/null @@ -1,775 +0,0 @@ -// -// 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_FLAG_H_ -#define ABSL_FLAGS_INTERNAL_FLAG_H_ - -#include <stddef.h> -#include <stdint.h> - -#include <atomic> -#include <cstring> -#include <memory> -#include <new> -#include <string> -#include <type_traits> -#include <typeinfo> - -#include "absl/base/attributes.h" -#include "absl/base/call_once.h" -#include "absl/base/config.h" -#include "absl/base/optimization.h" -#include "absl/base/thread_annotations.h" -#include "absl/flags/commandlineflag.h" -#include "absl/flags/config.h" -#include "absl/flags/internal/commandlineflag.h" -#include "absl/flags/internal/registry.h" -#include "absl/flags/marshalling.h" -#include "absl/meta/type_traits.h" -#include "absl/strings/string_view.h" -#include "absl/synchronization/mutex.h" -#include "absl/utility/utility.h" - -namespace absl { -ABSL_NAMESPACE_BEGIN - -/////////////////////////////////////////////////////////////////////////////// -// Forward declaration of absl::Flag<T> public API. -namespace flags_internal { -template <typename T> -class Flag; -} // namespace flags_internal - -#if defined(_MSC_VER) && !defined(__clang__) -template <typename T> -class Flag; -#else -template <typename T> -using Flag = flags_internal::Flag<T>; -#endif - -template <typename T> -ABSL_MUST_USE_RESULT T GetFlag(const absl::Flag<T>& flag); - -template <typename T> -void SetFlag(absl::Flag<T>* flag, const T& v); - -template <typename T, typename V> -void SetFlag(absl::Flag<T>* flag, const V& v); - -template <typename U> -const CommandLineFlag& GetFlagReflectionHandle(const absl::Flag<U>& f); - -/////////////////////////////////////////////////////////////////////////////// -// Flag value type operations, eg., parsing, copying, etc. are provided -// by function specific to that type with a signature matching FlagOpFn. - -namespace flags_internal { - -enum class FlagOp { - kAlloc, - kDelete, - kCopy, - kCopyConstruct, - kSizeof, - kFastTypeId, - kRuntimeTypeId, - kParse, - kUnparse, - kValueOffset, -}; -using FlagOpFn = void* (*)(FlagOp, const void*, void*, void*); - -// Forward declaration for Flag value specific operations. -template <typename T> -void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3); - -// Allocate aligned memory for a flag value. -inline void* Alloc(FlagOpFn op) { - return op(FlagOp::kAlloc, nullptr, nullptr, nullptr); -} -// Deletes memory interpreting obj as flag value type pointer. -inline void Delete(FlagOpFn op, void* obj) { - op(FlagOp::kDelete, nullptr, obj, nullptr); -} -// Copies src to dst interpreting as flag value type pointers. -inline void Copy(FlagOpFn op, const void* src, void* dst) { - op(FlagOp::kCopy, src, dst, nullptr); -} -// Construct a copy of flag value in a location pointed by dst -// based on src - pointer to the flag's value. -inline void CopyConstruct(FlagOpFn op, const void* src, void* dst) { - op(FlagOp::kCopyConstruct, src, dst, nullptr); -} -// Makes a copy of flag value pointed by obj. -inline void* Clone(FlagOpFn op, const void* obj) { - void* res = flags_internal::Alloc(op); - flags_internal::CopyConstruct(op, obj, res); - return res; -} -// Returns true if parsing of input text is successfull. -inline bool Parse(FlagOpFn op, absl::string_view text, void* dst, - std::string* error) { - return op(FlagOp::kParse, &text, dst, error) != nullptr; -} -// Returns string representing supplied value. -inline std::string Unparse(FlagOpFn op, const void* val) { - std::string result; - op(FlagOp::kUnparse, val, &result, nullptr); - return result; -} -// Returns size of flag value type. -inline size_t Sizeof(FlagOpFn op) { - // This sequence of casts reverses the sequence from - // `flags_internal::FlagOps()` - return static_cast<size_t>(reinterpret_cast<intptr_t>( - op(FlagOp::kSizeof, nullptr, nullptr, nullptr))); -} -// Returns fast type id coresponding to the value type. -inline FlagFastTypeId FastTypeId(FlagOpFn op) { - return reinterpret_cast<FlagFastTypeId>( - op(FlagOp::kFastTypeId, nullptr, nullptr, nullptr)); -} -// Returns fast type id coresponding to the value type. -inline const std::type_info* RuntimeTypeId(FlagOpFn op) { - return reinterpret_cast<const std::type_info*>( - op(FlagOp::kRuntimeTypeId, nullptr, nullptr, nullptr)); -} -// Returns offset of the field value_ from the field impl_ inside of -// absl::Flag<T> data. Given FlagImpl pointer p you can get the -// location of the corresponding value as: -// reinterpret_cast<char*>(p) + ValueOffset(). -inline ptrdiff_t ValueOffset(FlagOpFn op) { - // This sequence of casts reverses the sequence from - // `flags_internal::FlagOps()` - return static_cast<ptrdiff_t>(reinterpret_cast<intptr_t>( - op(FlagOp::kValueOffset, nullptr, nullptr, nullptr))); -} - -// Returns an address of RTTI's typeid(T). -template <typename T> -inline const std::type_info* GenRuntimeTypeId() { -#if defined(ABSL_FLAGS_INTERNAL_HAS_RTTI) - return &typeid(T); -#else - return nullptr; -#endif -} - -/////////////////////////////////////////////////////////////////////////////// -// Flag help auxiliary structs. - -// This is help argument for absl::Flag encapsulating the string literal pointer -// or pointer to function generating it as well as enum descriminating two -// cases. -using HelpGenFunc = std::string (*)(); - -template <size_t N> -struct FixedCharArray { - char value[N]; - - template <size_t... I> - static constexpr FixedCharArray<N> FromLiteralString( - absl::string_view str, absl::index_sequence<I...>) { - return (void)str, FixedCharArray<N>({{str[I]..., '\0'}}); - } -}; - -template <typename Gen, size_t N = Gen::Value().size()> -constexpr FixedCharArray<N + 1> HelpStringAsArray(int) { - return FixedCharArray<N + 1>::FromLiteralString( - Gen::Value(), absl::make_index_sequence<N>{}); -} - -template <typename Gen> -constexpr std::false_type HelpStringAsArray(char) { - return std::false_type{}; -} - -union FlagHelpMsg { - constexpr explicit FlagHelpMsg(const char* help_msg) : literal(help_msg) {} - constexpr explicit FlagHelpMsg(HelpGenFunc help_gen) : gen_func(help_gen) {} - - const char* literal; - HelpGenFunc gen_func; -}; - -enum class FlagHelpKind : uint8_t { kLiteral = 0, kGenFunc = 1 }; - -struct FlagHelpArg { - FlagHelpMsg source; - FlagHelpKind kind; -}; - -extern const char kStrippedFlagHelp[]; - -// These two HelpArg overloads allows us to select at compile time one of two -// way to pass Help argument to absl::Flag. We'll be passing -// AbslFlagHelpGenFor##name as Gen and integer 0 as a single argument to prefer -// first overload if possible. If help message is evaluatable on constexpr -// context We'll be able to make FixedCharArray out of it and we'll choose first -// overload. In this case the help message expression is immediately evaluated -// and is used to construct the absl::Flag. No additionl code is generated by -// ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the -// consideration, in which case the second overload will be used. The second -// overload does not attempt to evaluate the help message expression -// immediately and instead delays the evaluation by returing the function -// pointer (&T::NonConst) genering the help message when necessary. This is -// evaluatable in constexpr context, but the cost is an extra function being -// generated in the ABSL_FLAG code. -template <typename Gen, size_t N> -constexpr FlagHelpArg HelpArg(const FixedCharArray<N>& value) { - return {FlagHelpMsg(value.value), FlagHelpKind::kLiteral}; -} - -template <typename Gen> -constexpr FlagHelpArg HelpArg(std::false_type) { - return {FlagHelpMsg(&Gen::NonConst), FlagHelpKind::kGenFunc}; -} - -/////////////////////////////////////////////////////////////////////////////// -// Flag default value auxiliary structs. - -// Signature for the function generating the initial flag value (usually -// based on default value supplied in flag's definition) -using FlagDfltGenFunc = void (*)(void*); - -union FlagDefaultSrc { - constexpr explicit FlagDefaultSrc(FlagDfltGenFunc gen_func_arg) - : gen_func(gen_func_arg) {} - -#define ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE(T, name) \ - T name##_value; \ - constexpr explicit FlagDefaultSrc(T value) : name##_value(value) {} // NOLINT - ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE) -#undef ABSL_FLAGS_INTERNAL_DFLT_FOR_TYPE - - void* dynamic_value; - FlagDfltGenFunc gen_func; -}; - -enum class FlagDefaultKind : uint8_t { - kDynamicValue = 0, - kGenFunc = 1, - kOneWord = 2 // for default values UP to one word in size -}; - -struct FlagDefaultArg { - FlagDefaultSrc source; - FlagDefaultKind kind; -}; - -// This struct and corresponding overload to InitDefaultValue are used to -// facilitate usage of {} as default value in ABSL_FLAG macro. -// TODO(rogeeff): Fix handling types with explicit constructors. -struct EmptyBraces {}; - -template <typename T> -constexpr T InitDefaultValue(T t) { - return t; -} - -template <typename T> -constexpr T InitDefaultValue(EmptyBraces) { - return T{}; -} - -template <typename ValueT, typename GenT, - typename std::enable_if<std::is_integral<ValueT>::value, int>::type = - (GenT{}, 0)> -constexpr FlagDefaultArg DefaultArg(int) { - return {FlagDefaultSrc(GenT{}.value), FlagDefaultKind::kOneWord}; -} - -template <typename ValueT, typename GenT> -constexpr FlagDefaultArg DefaultArg(char) { - return {FlagDefaultSrc(&GenT::Gen), FlagDefaultKind::kGenFunc}; -} - -/////////////////////////////////////////////////////////////////////////////// -// Flag current value auxiliary structs. - -constexpr int64_t UninitializedFlagValue() { return 0xababababababababll; } - -template <typename T> -using FlagUseOneWordStorage = std::integral_constant< - bool, absl::type_traits_internal::is_trivially_copyable<T>::value && - (sizeof(T) <= 8)>; - -#if defined(ABSL_FLAGS_INTERNAL_ATOMIC_DOUBLE_WORD) -// Clang does not always produce cmpxchg16b instruction when alignment of a 16 -// bytes type is not 16. -struct alignas(16) AlignedTwoWords { - int64_t first; - int64_t second; - - bool IsInitialized() const { - return first != flags_internal::UninitializedFlagValue(); - } -}; - -template <typename T> -using FlagUseTwoWordsStorage = std::integral_constant< - bool, absl::type_traits_internal::is_trivially_copyable<T>::value && - (sizeof(T) > 8) && (sizeof(T) <= 16)>; -#else -// This is actually unused and only here to avoid ifdefs in other palces. -struct AlignedTwoWords { - constexpr AlignedTwoWords() noexcept : dummy() {} - constexpr AlignedTwoWords(int64_t, int64_t) noexcept : dummy() {} - char dummy; - - bool IsInitialized() const { - std::abort(); - return true; - } -}; - -// This trait should be type dependent, otherwise SFINAE below will fail -template <typename T> -using FlagUseTwoWordsStorage = - std::integral_constant<bool, sizeof(T) != sizeof(T)>; -#endif - -template <typename T> -using FlagUseBufferStorage = - std::integral_constant<bool, !FlagUseOneWordStorage<T>::value && - !FlagUseTwoWordsStorage<T>::value>; - -enum class FlagValueStorageKind : uint8_t { - kAlignedBuffer = 0, - kOneWordAtomic = 1, - kTwoWordsAtomic = 2 -}; - -template <typename T> -static constexpr FlagValueStorageKind StorageKind() { - return FlagUseBufferStorage<T>::value - ? FlagValueStorageKind::kAlignedBuffer - : FlagUseOneWordStorage<T>::value - ? FlagValueStorageKind::kOneWordAtomic - : FlagValueStorageKind::kTwoWordsAtomic; -} - -struct FlagOneWordValue { - constexpr FlagOneWordValue() : value(UninitializedFlagValue()) {} - - std::atomic<int64_t> value; -}; - -struct FlagTwoWordsValue { - constexpr FlagTwoWordsValue() - : value(AlignedTwoWords{UninitializedFlagValue(), 0}) {} - - std::atomic<AlignedTwoWords> value; -}; - -template <typename T, - FlagValueStorageKind Kind = flags_internal::StorageKind<T>()> -struct FlagValue; - -template <typename T> -struct FlagValue<T, FlagValueStorageKind::kAlignedBuffer> { - bool Get(T&) const { return false; } - - alignas(T) char value[sizeof(T)]; -}; - -template <typename T> -struct FlagValue<T, FlagValueStorageKind::kOneWordAtomic> : FlagOneWordValue { - bool Get(T& dst) const { - int64_t one_word_val = value.load(std::memory_order_acquire); - if (ABSL_PREDICT_FALSE(one_word_val == UninitializedFlagValue())) { - return false; - } - std::memcpy(&dst, static_cast<const void*>(&one_word_val), sizeof(T)); - return true; - } -}; - -template <typename T> -struct FlagValue<T, FlagValueStorageKind::kTwoWordsAtomic> : FlagTwoWordsValue { - bool Get(T& dst) const { - AlignedTwoWords two_words_val = value.load(std::memory_order_acquire); - if (ABSL_PREDICT_FALSE(!two_words_val.IsInitialized())) { - return false; - } - std::memcpy(&dst, static_cast<const void*>(&two_words_val), sizeof(T)); - return true; - } -}; - -/////////////////////////////////////////////////////////////////////////////// -// Flag callback auxiliary structs. - -// Signature for the mutation callback used by watched Flags -// The callback is noexcept. -// TODO(rogeeff): add noexcept after C++17 support is added. -using FlagCallbackFunc = void (*)(); - -struct FlagCallback { - FlagCallbackFunc func; - absl::Mutex guard; // Guard for concurrent callback invocations. -}; - -/////////////////////////////////////////////////////////////////////////////// -// Flag implementation, which does not depend on flag value type. -// The class encapsulates the Flag's data and access to it. - -struct DynValueDeleter { - explicit DynValueDeleter(FlagOpFn op_arg = nullptr); - void operator()(void* ptr) const; - - FlagOpFn op; -}; - -class FlagState; - -class FlagImpl final : public CommandLineFlag { - public: - constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op, - FlagHelpArg help, FlagValueStorageKind value_kind, - FlagDefaultArg default_arg) - : name_(name), - filename_(filename), - op_(op), - help_(help.source), - help_source_kind_(static_cast<uint8_t>(help.kind)), - value_storage_kind_(static_cast<uint8_t>(value_kind)), - def_kind_(static_cast<uint8_t>(default_arg.kind)), - modified_(false), - on_command_line_(false), - counter_(0), - callback_(nullptr), - default_value_(default_arg.source), - data_guard_{} {} - - // Constant access methods - void Read(void* dst) const override ABSL_LOCKS_EXCLUDED(*DataGuard()); - - // Mutating access methods - void Write(const void* src) ABSL_LOCKS_EXCLUDED(*DataGuard()); - - // Interfaces to operate on callbacks. - void SetCallback(const FlagCallbackFunc mutation_callback) - ABSL_LOCKS_EXCLUDED(*DataGuard()); - void InvokeCallback() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); - - // Used in read/write operations to validate source/target has correct type. - // For example if flag is declared as absl::Flag<int> FLAGS_foo, a call to - // absl::GetFlag(FLAGS_foo) validates that the type of FLAGS_foo is indeed - // int. To do that we pass the "assumed" type id (which is deduced from type - // int) as an argument `type_id`, which is in turn is validated against the - // type id stored in flag object by flag definition statement. - void AssertValidType(FlagFastTypeId type_id, - const std::type_info* (*gen_rtti)()) const; - - private: - template <typename T> - friend class Flag; - friend class FlagState; - - // Ensures that `data_guard_` is initialized and returns it. - absl::Mutex* DataGuard() const - ABSL_LOCK_RETURNED(reinterpret_cast<absl::Mutex*>(data_guard_)); - // Returns heap allocated value of type T initialized with default value. - std::unique_ptr<void, DynValueDeleter> MakeInitValue() const - ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); - // Flag initialization called via absl::call_once. - void Init(); - - // Offset value access methods. One per storage kind. These methods to not - // respect const correctness, so be very carefull using them. - - // This is a shared helper routine which encapsulates most of the magic. Since - // it is only used inside the three routines below, which are defined in - // flag.cc, we can define it in that file as well. - template <typename StorageT> - StorageT* OffsetValue() const; - // This is an accessor for a value stored in an aligned buffer storage. - // Returns a mutable pointer to the start of a buffer. - void* AlignedBufferValue() const; - // This is an accessor for a value stored as one word atomic. Returns a - // mutable reference to an atomic value. - std::atomic<int64_t>& OneWordValue() const; - // This is an accessor for a value stored as two words atomic. Returns a - // mutable reference to an atomic value. - std::atomic<AlignedTwoWords>& TwoWordsValue() const; - - // Attempts to parse supplied `value` string. If parsing is successful, - // returns new value. Otherwise returns nullptr. - std::unique_ptr<void, DynValueDeleter> TryParse(absl::string_view value, - std::string& err) const - ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); - // Stores the flag value based on the pointer to the source. - void StoreValue(const void* src) ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()); - - FlagHelpKind HelpSourceKind() const { - return static_cast<FlagHelpKind>(help_source_kind_); - } - FlagValueStorageKind ValueStorageKind() const { - return static_cast<FlagValueStorageKind>(value_storage_kind_); - } - FlagDefaultKind DefaultKind() const - ABSL_EXCLUSIVE_LOCKS_REQUIRED(*DataGuard()) { - return static_cast<FlagDefaultKind>(def_kind_); - } - - // CommandLineFlag interface implementation - absl::string_view Name() const override; - std::string Filename() const override; - std::string Help() const override; - FlagFastTypeId TypeId() const override; - bool IsSpecifiedOnCommandLine() const override - ABSL_LOCKS_EXCLUDED(*DataGuard()); - std::string DefaultValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard()); - std::string CurrentValue() const override ABSL_LOCKS_EXCLUDED(*DataGuard()); - bool ValidateInputValue(absl::string_view value) const override - ABSL_LOCKS_EXCLUDED(*DataGuard()); - void CheckDefaultValueParsingRoundtrip() const override - ABSL_LOCKS_EXCLUDED(*DataGuard()); - - // Interfaces to save and restore flags to/from persistent state. - // Returns current flag state or nullptr if flag does not support - // saving and restoring a state. - std::unique_ptr<FlagStateInterface> SaveState() override - ABSL_LOCKS_EXCLUDED(*DataGuard()); - - // Restores the flag state to the supplied state object. If there is - // nothing to restore returns false. Otherwise returns true. - bool RestoreState(const FlagState& flag_state) - ABSL_LOCKS_EXCLUDED(*DataGuard()); - - bool ParseFrom(absl::string_view value, FlagSettingMode set_mode, - ValueSource source, std::string& error) override - ABSL_LOCKS_EXCLUDED(*DataGuard()); - - // Immutable flag's state. - - // Flags name passed to ABSL_FLAG as second arg. - const char* const name_; - // The file name where ABSL_FLAG resides. - const char* const filename_; - // Type-specific operations "vtable". - const FlagOpFn op_; - // Help message literal or function to generate it. - const FlagHelpMsg help_; - // Indicates if help message was supplied as literal or generator func. - const uint8_t help_source_kind_ : 1; - // Kind of storage this flag is using for the flag's value. - const uint8_t value_storage_kind_ : 2; - - uint8_t : 0; // The bytes containing the const bitfields must not be - // shared with bytes containing the mutable bitfields. - - // Mutable flag's state (guarded by `data_guard_`). - - // def_kind_ is not guard by DataGuard() since it is accessed in Init without - // locks. - uint8_t def_kind_ : 2; - // Has this flag's value been modified? - bool modified_ : 1 ABSL_GUARDED_BY(*DataGuard()); - // Has this flag been specified on command line. - bool on_command_line_ : 1 ABSL_GUARDED_BY(*DataGuard()); - - // Unique tag for absl::call_once call to initialize this flag. - absl::once_flag init_control_; - - // Mutation counter - int64_t counter_ ABSL_GUARDED_BY(*DataGuard()); - // Optional flag's callback and absl::Mutex to guard the invocations. - FlagCallback* callback_ ABSL_GUARDED_BY(*DataGuard()); - // Either a pointer to the function generating the default value based on the - // value specified in ABSL_FLAG or pointer to the dynamically set default - // value via SetCommandLineOptionWithMode. def_kind_ is used to distinguish - // these two cases. - FlagDefaultSrc default_value_; - - // This is reserved space for an absl::Mutex to guard flag data. It will be - // initialized in FlagImpl::Init via placement new. - // We can't use "absl::Mutex data_guard_", since this class is not literal. - // We do not want to use "absl::Mutex* data_guard_", since this would require - // heap allocation during initialization, which is both slows program startup - // and can fail. Using reserved space + placement new allows us to avoid both - // problems. - alignas(absl::Mutex) mutable char data_guard_[sizeof(absl::Mutex)]; -}; - -/////////////////////////////////////////////////////////////////////////////// -// The Flag object parameterized by the flag's value type. This class implements -// flag reflection handle interface. - -template <typename T> -class Flag { - public: - constexpr Flag(const char* name, const char* filename, FlagHelpArg help, - const FlagDefaultArg default_arg) - : impl_(name, filename, &FlagOps<T>, help, - flags_internal::StorageKind<T>(), default_arg), - value_() {} - - // CommandLineFlag interface - absl::string_view Name() const { return impl_.Name(); } - std::string Filename() const { return impl_.Filename(); } - std::string Help() const { return impl_.Help(); } - // Do not use. To be removed. - bool IsSpecifiedOnCommandLine() const { - return impl_.IsSpecifiedOnCommandLine(); - } - std::string DefaultValue() const { return impl_.DefaultValue(); } - std::string CurrentValue() const { return impl_.CurrentValue(); } - - private: - template <typename, bool> - friend class FlagRegistrar; - friend class FlagImplPeer; - - T Get() const { - // See implementation notes in CommandLineFlag::Get(). - union U { - T value; - U() {} - ~U() { value.~T(); } - }; - U u; - -#if !defined(NDEBUG) - impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>); -#endif - - if (!value_.Get(u.value)) impl_.Read(&u.value); - return std::move(u.value); - } - void Set(const T& v) { - impl_.AssertValidType(base_internal::FastTypeId<T>(), &GenRuntimeTypeId<T>); - impl_.Write(&v); - } - - // Access to the reflection. - const CommandLineFlag& Reflect() const { return impl_; } - - // Flag's data - // The implementation depends on value_ field to be placed exactly after the - // impl_ field, so that impl_ can figure out the offset to the value and - // access it. - FlagImpl impl_; - FlagValue<T> value_; -}; - -/////////////////////////////////////////////////////////////////////////////// -// Trampoline for friend access - -class FlagImplPeer { - public: - template <typename T, typename FlagType> - static T InvokeGet(const FlagType& flag) { - return flag.Get(); - } - template <typename FlagType, typename T> - static void InvokeSet(FlagType& flag, const T& v) { - flag.Set(v); - } - template <typename FlagType> - static const CommandLineFlag& InvokeReflect(const FlagType& f) { - return f.Reflect(); - } -}; - -/////////////////////////////////////////////////////////////////////////////// -// Implementation of Flag value specific operations routine. -template <typename T> -void* FlagOps(FlagOp op, const void* v1, void* v2, void* v3) { - switch (op) { - case FlagOp::kAlloc: { - std::allocator<T> alloc; - return std::allocator_traits<std::allocator<T>>::allocate(alloc, 1); - } - case FlagOp::kDelete: { - T* p = static_cast<T*>(v2); - p->~T(); - std::allocator<T> alloc; - std::allocator_traits<std::allocator<T>>::deallocate(alloc, p, 1); - return nullptr; - } - case FlagOp::kCopy: - *static_cast<T*>(v2) = *static_cast<const T*>(v1); - return nullptr; - case FlagOp::kCopyConstruct: - new (v2) T(*static_cast<const T*>(v1)); - return nullptr; - case FlagOp::kSizeof: - return reinterpret_cast<void*>(static_cast<uintptr_t>(sizeof(T))); - case FlagOp::kFastTypeId: - return const_cast<void*>(base_internal::FastTypeId<T>()); - case FlagOp::kRuntimeTypeId: - return const_cast<std::type_info*>(GenRuntimeTypeId<T>()); - case FlagOp::kParse: { - // Initialize the temporary instance of type T based on current value in - // destination (which is going to be flag's default value). - T temp(*static_cast<T*>(v2)); - if (!absl::ParseFlag<T>(*static_cast<const absl::string_view*>(v1), &temp, - static_cast<std::string*>(v3))) { - return nullptr; - } - *static_cast<T*>(v2) = std::move(temp); - return v2; - } - case FlagOp::kUnparse: - *static_cast<std::string*>(v2) = - absl::UnparseFlag<T>(*static_cast<const T*>(v1)); - return nullptr; - case FlagOp::kValueOffset: { - // Round sizeof(FlagImp) to a multiple of alignof(FlagValue<T>) to get the - // offset of the data. - ptrdiff_t round_to = alignof(FlagValue<T>); - ptrdiff_t offset = - (sizeof(FlagImpl) + round_to - 1) / round_to * round_to; - return reinterpret_cast<void*>(offset); - } - } - return nullptr; -} - -/////////////////////////////////////////////////////////////////////////////// -// This class facilitates Flag object registration and tail expression-based -// flag definition, for example: -// ABSL_FLAG(int, foo, 42, "Foo help").OnUpdate(NotifyFooWatcher); -struct FlagRegistrarEmpty {}; -template <typename T, bool do_register> -class FlagRegistrar { - public: - explicit FlagRegistrar(Flag<T>& flag) : flag_(flag) { - if (do_register) flags_internal::RegisterCommandLineFlag(flag_.impl_); - } - - FlagRegistrar OnUpdate(FlagCallbackFunc cb) && { - flag_.impl_.SetCallback(cb); - return *this; - } - - // Make the registrar "die" gracefully as an empty struct on a line where - // registration happens. Registrar objects are intended to live only as - // temporary. - operator FlagRegistrarEmpty() const { return {}; } // NOLINT - - private: - Flag<T>& flag_; // Flag being registered (not owned). -}; - -} // namespace flags_internal -ABSL_NAMESPACE_END -} // namespace absl - -#endif // ABSL_FLAGS_INTERNAL_FLAG_H_ |