Abseil Common Libraries (C++) (grcp 依赖) https://abseil.io/
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//
// 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.
#include "absl/flags/internal/registry.h"
#include <assert.h>
#include <stdlib.h>
#include <functional>
#include <map>
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "absl/base/config.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/thread_annotations.h"
#include "absl/flags/internal/commandlineflag.h"
#include "absl/flags/usage_config.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
// --------------------------------------------------------------------
// FlagRegistry implementation
// A FlagRegistry holds all flag objects indexed
// by their names so that if you know a flag's name you can access or
// set it.
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace flags_internal {
// --------------------------------------------------------------------
// FlagRegistry
// A FlagRegistry singleton object holds all flag objects indexed
// by their names so that if you know a flag's name (as a C
// string), you can access or set it. If the function is named
// FooLocked(), you must own the registry lock before calling
// the function; otherwise, you should *not* hold the lock, and
// the function will acquire it itself if needed.
// --------------------------------------------------------------------
class FlagRegistry {
public:
FlagRegistry() = default;
~FlagRegistry() = default;
// Store a flag in this registry. Takes ownership of *flag.
void RegisterFlag(CommandLineFlag* flag);
void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }
void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }
// Returns the flag object for the specified name, or nullptr if not found.
// Will emit a warning if a 'retired' flag is specified.
CommandLineFlag* FindFlagLocked(absl::string_view name);
// Returns the retired flag object for the specified name, or nullptr if not
// found or not retired. Does not emit a warning.
CommandLineFlag* FindRetiredFlagLocked(absl::string_view name);
static FlagRegistry* GlobalRegistry(); // returns a singleton registry
private:
friend class FlagSaverImpl; // reads all the flags in order to copy them
friend void ForEachFlagUnlocked(
std::function<void(CommandLineFlag*)> visitor);
// The map from name to flag, for FindFlagLocked().
using FlagMap = std::map<absl::string_view, CommandLineFlag*>;
using FlagIterator = FlagMap::iterator;
using FlagConstIterator = FlagMap::const_iterator;
FlagMap flags_;
absl::Mutex lock_;
// Disallow
FlagRegistry(const FlagRegistry&);
FlagRegistry& operator=(const FlagRegistry&);
};
FlagRegistry* FlagRegistry::GlobalRegistry() {
static FlagRegistry* global_registry = new FlagRegistry;
return global_registry;
}
namespace {
class FlagRegistryLock {
public:
explicit FlagRegistryLock(FlagRegistry* fr) : fr_(fr) { fr_->Lock(); }
~FlagRegistryLock() { fr_->Unlock(); }
private:
FlagRegistry* const fr_;
};
void DestroyRetiredFlag(CommandLineFlag* flag);
} // namespace
void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
FlagRegistryLock registry_lock(this);
std::pair<FlagIterator, bool> ins =
flags_.insert(FlagMap::value_type(flag->Name(), flag));
if (ins.second == false) { // means the name was already in the map
CommandLineFlag* old_flag = ins.first->second;
if (flag->IsRetired() != old_flag->IsRetired()) {
// All registrations must agree on the 'retired' flag.
flags_internal::ReportUsageError(
absl::StrCat(
"Retired flag '", flag->Name(),
"' was defined normally in file '",
(flag->IsRetired() ? old_flag->Filename() : flag->Filename()),
"'."),
true);
} else if (flag->TypeId() != old_flag->TypeId()) {
flags_internal::ReportUsageError(
absl::StrCat("Flag '", flag->Name(),
"' was defined more than once but with "
"differing types. Defined in files '",
old_flag->Filename(), "' and '", flag->Filename(),
"' with types '", old_flag->Typename(), "' and '",
flag->Typename(), "', respectively."),
true);
} else if (old_flag->IsRetired()) {
// Retired flag can just be deleted.
DestroyRetiredFlag(flag);
return;
} else if (old_flag->Filename() != flag->Filename()) {
flags_internal::ReportUsageError(
absl::StrCat("Flag '", flag->Name(),
"' was defined more than once (in files '",
old_flag->Filename(), "' and '", flag->Filename(),
"')."),
true);
} else {
flags_internal::ReportUsageError(
absl::StrCat(
"Something wrong with flag '", flag->Name(), "' in file '",
flag->Filename(), "'. One possibility: file '", flag->Filename(),
"' is being linked both statically and dynamically into this "
"executable. e.g. some files listed as srcs to a test and also "
"listed as srcs of some shared lib deps of the same test."),
true);
}
// All cases above are fatal, except for the retired flags.
std::exit(1);
}
}
CommandLineFlag* FlagRegistry::FindFlagLocked(absl::string_view name) {
FlagConstIterator i = flags_.find(name);
if (i == flags_.end()) {
return nullptr;
}
if (i->second->IsRetired()) {
flags_internal::ReportUsageError(
absl::StrCat("Accessing retired flag '", name, "'"), false);
}
return i->second;
}
CommandLineFlag* FlagRegistry::FindRetiredFlagLocked(absl::string_view name) {
FlagConstIterator i = flags_.find(name);
if (i == flags_.end() || !i->second->IsRetired()) {
return nullptr;
}
return i->second;
}
// --------------------------------------------------------------------
// FlagSaver
// FlagSaverImpl
// This class stores the states of all flags at construct time,
// and restores all flags to that state at destruct time.
// Its major implementation challenge is that it never modifies
// pointers in the 'main' registry, so global FLAG_* vars always
// point to the right place.
// --------------------------------------------------------------------
class FlagSaverImpl {
public:
FlagSaverImpl() = default;
FlagSaverImpl(const FlagSaverImpl&) = delete;
void operator=(const FlagSaverImpl&) = delete;
// Saves the flag states from the flag registry into this object.
// It's an error to call this more than once.
void SaveFromRegistry() {
assert(backup_registry_.empty()); // call only once!
flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
if (auto flag_state = flag->SaveState()) {
backup_registry_.emplace_back(std::move(flag_state));
}
});
}
// Restores the saved flag states into the flag registry.
void RestoreToRegistry() {
for (const auto& flag_state : backup_registry_) {
flag_state->Restore();
}
}
private:
std::vector<std::unique_ptr<flags_internal::FlagStateInterface>>
backup_registry_;
};
FlagSaver::FlagSaver() : impl_(new FlagSaverImpl) { impl_->SaveFromRegistry(); }
void FlagSaver::Ignore() {
delete impl_;
impl_ = nullptr;
}
FlagSaver::~FlagSaver() {
if (!impl_) return;
impl_->RestoreToRegistry();
delete impl_;
}
// --------------------------------------------------------------------
CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
if (name.empty()) return nullptr;
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
return registry->FindFlagLocked(name);
}
CommandLineFlag* FindRetiredFlag(absl::string_view name) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
return registry->FindRetiredFlagLocked(name);
}
// --------------------------------------------------------------------
void ForEachFlagUnlocked(std::function<void(CommandLineFlag*)> visitor) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
for (FlagRegistry::FlagConstIterator i = registry->flags_.begin();
i != registry->flags_.end(); ++i) {
visitor(i->second);
}
}
void ForEachFlag(std::function<void(CommandLineFlag*)> visitor) {
FlagRegistry* const registry = FlagRegistry::GlobalRegistry();
FlagRegistryLock frl(registry);
ForEachFlagUnlocked(visitor);
}
// --------------------------------------------------------------------
bool RegisterCommandLineFlag(CommandLineFlag* flag) {
FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
return true;
}
// --------------------------------------------------------------------
namespace {
class RetiredFlagObj final : public flags_internal::CommandLineFlag {
public:
constexpr RetiredFlagObj(const char* name, FlagStaticTypeId type_id)
: name_(name), type_id_(type_id) {}
private:
absl::string_view Name() const override { return name_; }
std::string Filename() const override { return "RETIRED"; }
absl::string_view Typename() const override { return ""; }
FlagStaticTypeId TypeId() const override { return type_id_; }
std::string Help() const override { return ""; }
bool IsRetired() const override { return true; }
bool IsModified() const override { return false; }
bool IsSpecifiedOnCommandLine() const override { return false; }
std::string DefaultValue() const override { return ""; }
std::string CurrentValue() const override { return ""; }
// Any input is valid
bool ValidateInputValue(absl::string_view) const override { return true; }
std::unique_ptr<flags_internal::FlagStateInterface> SaveState() override {
return nullptr;
}
bool ParseFrom(absl::string_view, flags_internal::FlagSettingMode,
flags_internal::ValueSource, std::string*) override {
return false;
}
void CheckDefaultValueParsingRoundtrip() const override {}
void Read(void*) const override {}
// Data members
const char* const name_;
const FlagStaticTypeId type_id_;
};
void DestroyRetiredFlag(flags_internal::CommandLineFlag* flag) {
assert(flag->IsRetired());
delete static_cast<RetiredFlagObj*>(flag);
}
} // namespace
bool Retire(const char* name, FlagStaticTypeId type_id) {
auto* flag = new flags_internal::RetiredFlagObj(name, type_id);
FlagRegistry::GlobalRegistry()->RegisterFlag(flag);
return true;
}
// --------------------------------------------------------------------
bool IsRetiredFlag(absl::string_view name, bool* type_is_bool) {
assert(!name.empty());
CommandLineFlag* flag = flags_internal::FindRetiredFlag(name);
if (flag == nullptr) {
return false;
}
assert(type_is_bool);
*type_is_bool = flag->IsOfType<bool>();
return true;
}
} // namespace flags_internal
ABSL_NAMESPACE_END
} // namespace absl