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-rw-r--r--absl/flags/internal/commandlineflag.h414
1 files changed, 121 insertions, 293 deletions
diff --git a/absl/flags/internal/commandlineflag.h b/absl/flags/internal/commandlineflag.h
index 382553d2..6363c661 100644
--- a/absl/flags/internal/commandlineflag.h
+++ b/absl/flags/internal/commandlineflag.h
@@ -16,30 +16,41 @@
#ifndef ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
#define ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
-#include <atomic>
+#include <stddef.h>
+#include <stdint.h>
+#include <memory>
+#include <string>
+#include <typeinfo>
+
+#include "absl/base/config.h"
#include "absl/base/macros.h"
+#include "absl/flags/config.h"
#include "absl/flags/marshalling.h"
-#include "absl/synchronization/mutex.h"
+#include "absl/strings/string_view.h"
#include "absl/types/optional.h"
namespace absl {
-inline namespace lts_2019_08_08 {
+ABSL_NAMESPACE_BEGIN
namespace flags_internal {
-// Type-specific operations, eg., parsing, copying, etc. are provided
-// by function specific to that type with a signature matching FlagOpFn.
-enum FlagOp {
- kDelete,
- kClone,
- kCopy,
- kCopyConstruct,
- kSizeof,
- kParse,
- kUnparse
-};
-using FlagOpFn = void* (*)(FlagOp, const void*, void*);
-using FlagMarshallingOpFn = void* (*)(FlagOp, const void*, void*, void*);
+// An alias for flag static type id. Values of type identify the flag value type
+// simialarly to typeid(T), but without relying on RTTI being available. In most
+// cases this id is enough to uniquely identify the flag's value type. In a few
+// cases we'll have to resort to using actual RTTI implementation if it is
+// available.
+using FlagStaticTypeId = void* (*)();
+
+// Address of this function template is used in current implementation as a flag
+// static type id.
+template <typename T>
+void* FlagStaticTypeIdGen() {
+#if defined(ABSL_FLAGS_INTERNAL_HAS_RTTI)
+ return const_cast<std::type_info*>(&typeid(T));
+#else
+ return nullptr;
+#endif
+}
// Options that control SetCommandLineOptionWithMode.
enum FlagSettingMode {
@@ -62,215 +73,95 @@ enum ValueSource {
kProgrammaticChange,
};
-// Signature for the help generation function used as an argument for the
-// absl::Flag constructor.
-using HelpGenFunc = std::string (*)();
-
-// Signature for the function generating the initial flag value based (usually
-// based on default value supplied in flag's definition)
-using InitialValGenFunc = void* (*)();
-
-struct CommandLineFlagInfo;
-
-// Signature for the mutation callback used by watched Flags
-// The callback is noexcept.
-// TODO(rogeeff): add noexcept after C++17 support is added.
-using FlagCallback = void (*)();
-
-using FlagValidator = bool (*)();
-
-extern const char kStrippedFlagHelp[];
-
-// The per-type function
-template <typename T>
-void* FlagOps(FlagOp op, const void* v1, void* v2) {
- switch (op) {
- case kDelete:
- delete static_cast<const T*>(v1);
- return nullptr;
- case kClone:
- return new T(*static_cast<const T*>(v1));
- case kCopy:
- *static_cast<T*>(v2) = *static_cast<const T*>(v1);
- return nullptr;
- case kCopyConstruct:
- new (v2) T(*static_cast<const T*>(v1));
- return nullptr;
- case kSizeof:
- return reinterpret_cast<void*>(sizeof(T));
- default:
- return nullptr;
- }
-}
-
-template <typename T>
-void* FlagMarshallingOps(FlagOp op, const void* v1, void* v2, void* v3) {
- switch (op) {
- case 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 kUnparse:
- *static_cast<std::string*>(v2) =
- absl::UnparseFlag<T>(*static_cast<const T*>(v1));
- return nullptr;
- default:
- return nullptr;
- }
-}
-
-// Functions that invoke flag-type-specific operations.
-inline void Delete(FlagOpFn op, const void* obj) {
- op(flags_internal::kDelete, obj, nullptr);
-}
-
-inline void* Clone(FlagOpFn op, const void* obj) {
- return op(flags_internal::kClone, obj, nullptr);
-}
-
-inline void Copy(FlagOpFn op, const void* src, void* dst) {
- op(flags_internal::kCopy, src, dst);
-}
-
-inline void CopyConstruct(FlagOpFn op, const void* src, void* dst) {
- op(flags_internal::kCopyConstruct, src, dst);
-}
-
-inline bool Parse(FlagMarshallingOpFn op, absl::string_view text, void* dst,
- std::string* error) {
- return op(flags_internal::kParse, &text, dst, error) != nullptr;
-}
-
-inline std::string Unparse(FlagMarshallingOpFn op, const void* val) {
- std::string result;
- op(flags_internal::kUnparse, val, &result, nullptr);
- return result;
-}
-
-inline size_t Sizeof(FlagOpFn op) {
- // This sequence of casts reverses the sequence from base::internal::FlagOps()
- return static_cast<size_t>(reinterpret_cast<intptr_t>(
- op(flags_internal::kSizeof, nullptr, nullptr)));
-}
-
-// The following struct contains the locks in a CommandLineFlag struct.
-// They are in a separate struct that is lazily allocated to avoid problems
-// with static initialization and to avoid multiple allocations.
-struct CommandLineFlagLocks {
- absl::Mutex primary_mu; // protects several fields in CommandLineFlag
- absl::Mutex callback_mu; // used to serialize callbacks
-};
-
-// Holds either a pointer to help text or a function which produces it. This is
-// needed for supporting both static initialization of Flags while supporting
-// the legacy registration framework. We can't use absl::variant<const char*,
-// const char*(*)()> since anybody passing 0 or nullptr in to a CommandLineFlag
-// would find an ambiguity.
-class HelpText {
+// Handle to FlagState objects. Specific flag state objects will restore state
+// of a flag produced this flag state from method CommandLineFlag::SaveState().
+class FlagStateInterface {
public:
- static constexpr HelpText FromFunctionPointer(const HelpGenFunc fn) {
- return HelpText(fn, nullptr);
- }
- static constexpr HelpText FromStaticCString(const char* msg) {
- return HelpText(nullptr, msg);
- }
-
- std::string GetHelpText() const;
-
- HelpText() = delete;
- HelpText(const HelpText&) = default;
- HelpText(HelpText&&) = default;
+ virtual ~FlagStateInterface() {}
- private:
- explicit constexpr HelpText(const HelpGenFunc fn, const char* msg)
- : help_function_(fn), help_message_(msg) {}
-
- HelpGenFunc help_function_;
- const char* help_message_;
+ // Restores the flag originated this object to the saved state.
+ virtual void Restore() const = 0;
};
// Holds all information for a flag.
-struct CommandLineFlag {
- constexpr CommandLineFlag(
- const char* name_arg, HelpText help_text, const char* filename_arg,
- const flags_internal::FlagOpFn op_arg,
- const flags_internal::FlagMarshallingOpFn marshalling_op_arg,
- const flags_internal::InitialValGenFunc initial_value_gen,
- const bool retired_arg, void* def_arg, void* cur_arg)
- : name(name_arg),
- help(help_text),
- filename(filename_arg),
- op(op_arg),
- marshalling_op(marshalling_op_arg),
- make_init_value(initial_value_gen),
- retired(retired_arg),
- inited(false),
- modified(false),
- on_command_line(false),
- validator(nullptr),
- callback(nullptr),
- def(def_arg),
- cur(cur_arg),
- counter(0),
- atomic(kAtomicInit),
- locks(nullptr) {}
-
- // Revert the init routine.
- void Destroy() const;
+class CommandLineFlag {
+ public:
+ constexpr CommandLineFlag() = default;
// Not copyable/assignable.
CommandLineFlag(const CommandLineFlag&) = delete;
CommandLineFlag& operator=(const CommandLineFlag&) = delete;
- absl::string_view Name() const { return name; }
- std::string Help() const { return help.GetHelpText(); }
- bool IsRetired() const { return this->retired; }
- bool IsModified() const;
- void SetModified(bool is_modified);
- bool IsSpecifiedOnCommandLine() const;
- // Returns true iff this is a handle to an Abseil Flag.
- bool IsAbseilFlag() const {
- // Set to null for V1 flags
- return this->make_init_value != nullptr;
- }
-
- absl::string_view Typename() const;
- std::string Filename() const;
- std::string DefaultValue() const;
- std::string CurrentValue() const;
-
- bool HasValidatorFn() const;
- bool SetValidatorFn(FlagValidator fn);
- bool InvokeValidator(const void* value) const;
+ // Non-polymorphic access methods.
// Return true iff flag has type T.
template <typename T>
inline bool IsOfType() const {
- return this->op == &flags_internal::FlagOps<T>;
+ return TypeId() == &flags_internal::FlagStaticTypeIdGen<T>;
}
// Attempts to retrieve the flag value. Returns value on success,
// absl::nullopt otherwise.
template <typename T>
absl::optional<T> Get() const {
- if (IsRetired() || flags_internal::FlagOps<T> != this->op)
+ if (IsRetired() || !IsOfType<T>()) {
return absl::nullopt;
+ }
- T res;
- Read(&res, flags_internal::FlagOps<T>);
-
- return res;
+ // Implementation notes:
+ //
+ // We are wrapping a union around the value of `T` to serve three purposes:
+ //
+ // 1. `U.value` has correct size and alignment for a value of type `T`
+ // 2. The `U.value` constructor is not invoked since U's constructor does
+ // not do it explicitly.
+ // 3. The `U.value` destructor is invoked since U's destructor does it
+ // explicitly. This makes `U` a kind of RAII wrapper around non default
+ // constructible value of T, which is destructed when we leave the
+ // scope. We do need to destroy U.value, which is constructed by
+ // CommandLineFlag::Read even though we left it in a moved-from state
+ // after std::move.
+ //
+ // All of this serves to avoid requiring `T` being default constructible.
+ union U {
+ T value;
+ U() {}
+ ~U() { value.~T(); }
+ };
+ U u;
+
+ Read(&u.value);
+ return std::move(u.value);
}
- void SetCallback(const flags_internal::FlagCallback mutation_callback);
- void InvokeCallback();
+ // Polymorphic access methods
+
+ // Returns name of this flag.
+ virtual absl::string_view Name() const = 0;
+ // Returns name of the file where this flag is defined.
+ virtual std::string Filename() const = 0;
+ // Returns name of the flag's value type for some built-in types or empty
+ // std::string.
+ virtual absl::string_view Typename() const = 0;
+ // Returns help message associated with this flag.
+ virtual std::string Help() const = 0;
+ // Returns true iff this object corresponds to retired flag.
+ virtual bool IsRetired() const { return false; }
+ // Returns true iff this is a handle to an Abseil Flag.
+ virtual bool IsAbseilFlag() const { return true; }
+ // Returns id of the flag's value type.
+ virtual FlagStaticTypeId TypeId() const = 0;
+ virtual bool IsModified() const = 0;
+ virtual bool IsSpecifiedOnCommandLine() const = 0;
+ virtual std::string DefaultValue() const = 0;
+ virtual std::string CurrentValue() const = 0;
+
+ // Interfaces to operate on validators.
+ virtual bool ValidateInputValue(absl::string_view value) const = 0;
+
+ // Interface to save flag to some persistent state. Returns current flag state
+ // or nullptr if flag does not support saving and restoring a state.
+ virtual std::unique_ptr<FlagStateInterface> SaveState() = 0;
// Sets the value of the flag based on specified std::string `value`. If the flag
// was successfully set to new value, it returns true. Otherwise, sets `error`
@@ -280,106 +171,43 @@ struct CommandLineFlag {
// * Update the flag's default value
// * Update the current flag value if it was never set before
// The mode is selected based on `set_mode` parameter.
- bool SetFromString(absl::string_view value,
- flags_internal::FlagSettingMode set_mode,
- flags_internal::ValueSource source, std::string* error);
-
- void StoreAtomic(size_t size);
+ virtual bool SetFromString(absl::string_view value,
+ flags_internal::FlagSettingMode set_mode,
+ flags_internal::ValueSource source,
+ std::string* error) = 0;
- void CheckDefaultValueParsingRoundtrip() const;
- // Invoke the flag validators for old flags.
- // TODO(rogeeff): implement proper validators for Abseil Flags
- bool ValidateDefaultValue() const;
- bool ValidateInputValue(absl::string_view value) const;
-
- // Constant configuration for a particular flag.
- private:
- const char* const name;
- const HelpText help;
- const char* const filename;
+ // Checks that flags default value can be converted to std::string and back to the
+ // flag's value type.
+ virtual void CheckDefaultValueParsingRoundtrip() const = 0;
protected:
- const FlagOpFn op; // Type-specific handler
- const FlagMarshallingOpFn marshalling_op; // Marshalling ops handler
- const InitialValGenFunc make_init_value; // Makes initial value for the flag
- const bool retired; // Is the flag retired?
- std::atomic<bool> inited; // fields have been lazily initialized
+ ~CommandLineFlag() = default;
- // Mutable state (guarded by locks->primary_mu).
- bool modified; // Has flag value been modified?
- bool on_command_line; // Specified on command line.
- FlagValidator validator; // Validator function, or nullptr
- FlagCallback callback; // Mutation callback, or nullptr
- void* def; // Lazily initialized pointer to default value
- void* cur; // Lazily initialized pointer to current value
- int64_t counter; // Mutation counter
-
- // For some types, a copy of the current value is kept in an atomically
- // accessible field.
- static const int64_t kAtomicInit = 0xababababababababll;
- std::atomic<int64_t> atomic;
-
- // Lazily initialized mutexes for this flag value. We cannot inline a
- // SpinLock or Mutex here because those have non-constexpr constructors and
- // so would prevent constant initialization of this type.
- // TODO(rogeeff): fix it once Mutex has constexpr constructor
- struct CommandLineFlagLocks* locks; // locks, laziliy allocated.
-
- // Ensure that the lazily initialized fields of *flag have been initialized,
- // and return the lock which should be locked when flag's state is mutated.
- absl::Mutex* InitFlagIfNecessary() const;
-
- // copy construct new value of flag's type in a memory referenced by dst
- // based on current flag's value
- void Read(void* dst, const flags_internal::FlagOpFn dst_op) const;
- // updates flag's value to *src (locked)
- void Write(const void* src, const flags_internal::FlagOpFn src_op);
-
- friend class FlagRegistry;
- friend class FlagPtrMap;
- friend class FlagSaverImpl;
- friend void FillCommandLineFlagInfo(CommandLineFlag* flag,
- CommandLineFlagInfo* result);
- friend bool TryParseLocked(CommandLineFlag* flag, void* dst,
- absl::string_view value, std::string* err);
- friend absl::Mutex* InitFlag(CommandLineFlag* flag);
+ private:
+ // Copy-construct a new value of the flag's type in a memory referenced by
+ // the dst based on the current flag's value.
+ virtual void Read(void* dst) const = 0;
};
-// Update any copy of the flag value that is stored in an atomic word.
-// In addition if flag has a mutation callback this function invokes it. While
-// callback is being invoked the primary flag's mutex is unlocked and it is
-// re-locked back after call to callback is completed. Callback invocation is
-// guarded by flag's secondary mutex instead which prevents concurrent callback
-// invocation. Note that it is possible for other thread to grab the primary
-// lock and update flag's value at any time during the callback invocation.
-// This is by design. Callback can get a value of the flag if necessary, but it
-// might be different from the value initiated the callback and it also can be
-// different by the time the callback invocation is completed.
-// Requires that *primary_lock be held in exclusive mode; it may be released
-// and reacquired by the implementation.
-void UpdateCopy(CommandLineFlag* flag);
-// Return true iff flag value was changed via direct-access.
-bool ChangedDirectly(CommandLineFlag* flag, const void* a, const void* b);
-
-// This macro is the "source of truth" for the list of supported flag types we
-// expect to perform lock free operations on. Specifically it generates code,
-// a one argument macro operating on a type, supplied as a macro argument, for
-// each type in the list.
-#define ABSL_FLAGS_INTERNAL_FOR_EACH_LOCK_FREE(A) \
- A(bool) \
- A(short) \
- A(unsigned short) \
- A(int) \
- A(unsigned int) \
- A(long) \
- A(unsigned long) \
- A(long long) \
- A(unsigned long long) \
- A(double) \
- A(float)
+// This macro is the "source of truth" for the list of supported flag built-in
+// types.
+#define ABSL_FLAGS_INTERNAL_BUILTIN_TYPES(A) \
+ A(bool) \
+ A(short) \
+ A(unsigned short) \
+ A(int) \
+ A(unsigned int) \
+ A(long) \
+ A(unsigned long) \
+ A(long long) \
+ A(unsigned long long) \
+ A(double) \
+ A(float) \
+ A(std::string) \
+ A(std::vector<std::string>)
} // namespace flags_internal
-} // inline namespace lts_2019_08_08
+ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_FLAGS_INTERNAL_COMMANDLINEFLAG_H_
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-18 12:07:05 +0000