THUAI6/CAPI/cpp/grpc/include/google/protobuf/stubs/mutex.h

// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef GOOGLE_PROTOBUF_STUBS_MUTEX_H_
#define GOOGLE_PROTOBUF_STUBS_MUTEX_H_

#include <mutex>

#ifdef GOOGLE_PROTOBUF_SUPPORT_WINDOWS_XP

#include <windows.h>

// GetMessage conflicts with GeneratedMessageReflection::GetMessage().
#ifdef GetMessage
#undef GetMessage
#endif

#endif

#include <google/protobuf/stubs/macros.h>

// Define thread-safety annotations for use below, if we are building with
// Clang.
#if defined(__clang__) && !defined(SWIG)
#define GOOGLE_PROTOBUF_ACQUIRE(...) \
    __attribute__((acquire_capability(__VA_ARGS__)))
#define GOOGLE_PROTOBUF_RELEASE(...) \
    __attribute__((release_capability(__VA_ARGS__)))
#define GOOGLE_PROTOBUF_SCOPED_CAPABILITY __attribute__((scoped_lockable))
#define GOOGLE_PROTOBUF_CAPABILITY(x) __attribute__((capability(x)))
#else
#define GOOGLE_PROTOBUF_ACQUIRE(...)
#define GOOGLE_PROTOBUF_RELEASE(...)
#define GOOGLE_PROTOBUF_SCOPED_CAPABILITY
#define GOOGLE_PROTOBUF_CAPABILITY(x)
#endif

#include <google/protobuf/port_def.inc>

// ===================================================================
// emulates google3/base/mutex.h
namespace google
{
    namespace protobuf
    {
        namespace internal
        {

#define GOOGLE_PROTOBUF_LINKER_INITIALIZED

#ifdef GOOGLE_PROTOBUF_SUPPORT_WINDOWS_XP

            // This class is a lightweight replacement for std::mutex on Windows platforms.
            // std::mutex does not work on Windows XP SP2 with the latest VC++ libraries,
            // because it utilizes the Concurrency Runtime that is only supported on Windows
            // XP SP3 and above.
            class PROTOBUF_EXPORT CriticalSectionLock
            {
            public:
                CriticalSectionLock()
                {
                    InitializeCriticalSection(&critical_section_);
                }
                ~CriticalSectionLock()
                {
                    DeleteCriticalSection(&critical_section_);
                }
                void lock()
                {
                    EnterCriticalSection(&critical_section_);
                }
                void unlock()
                {
                    LeaveCriticalSection(&critical_section_);
                }

            private:
                CRITICAL_SECTION critical_section_;

                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CriticalSectionLock);
            };

#endif

            // In MSVC std::mutex does not have a constexpr constructor.
            // This wrapper makes the constructor constexpr.
            template<typename T>
            class CallOnceInitializedMutex
            {
            public:
                constexpr CallOnceInitializedMutex() :
                    flag_{},
                    buf_{}
                {
                }
                ~CallOnceInitializedMutex()
                {
                    get().~T();
                }

                void lock()
                {
                    get().lock();
                }
                void unlock()
                {
                    get().unlock();
                }

            private:
                T& get()
                {
                    std::call_once(flag_, [&]
                                   { ::new (static_cast<void*>(&buf_)) T(); });
                    return reinterpret_cast<T&>(buf_);
                }

                std::once_flag flag_;
                alignas(T) char buf_[sizeof(T)];
            };

            // Mutex is a natural type to wrap. As both google and other organization have
            // specialized mutexes. gRPC also provides an injection mechanism for custom
            // mutexes.
            class GOOGLE_PROTOBUF_CAPABILITY("mutex") PROTOBUF_EXPORT WrappedMutex
            {
            public:
#if defined(__QNX__)
                constexpr WrappedMutex() = default;
#else
                constexpr WrappedMutex()
                {
                }
#endif
                void Lock() GOOGLE_PROTOBUF_ACQUIRE()
                {
                    mu_.lock();
                }
                void Unlock() GOOGLE_PROTOBUF_RELEASE()
                {
                    mu_.unlock();
                }
                // Crash if this Mutex is not held exclusively by this thread.
                // May fail to crash when it should; will never crash when it should not.
                void AssertHeld() const
                {
                }

            private:
#if defined(GOOGLE_PROTOBUF_SUPPORT_WINDOWS_XP)
                CallOnceInitializedMutex<CriticalSectionLock> mu_{};
#elif defined(_WIN32)
                CallOnceInitializedMutex<std::mutex> mu_{};
#else
                std::mutex mu_{};
#endif
            };

            using Mutex = WrappedMutex;

            // MutexLock(mu) acquires mu when constructed and releases it when destroyed.
            class GOOGLE_PROTOBUF_SCOPED_CAPABILITY PROTOBUF_EXPORT MutexLock
            {
            public:
                explicit MutexLock(Mutex* mu) GOOGLE_PROTOBUF_ACQUIRE(mu) :
                    mu_(mu)
                {
                    this->mu_->Lock();
                }
                ~MutexLock() GOOGLE_PROTOBUF_RELEASE()
                {
                    this->mu_->Unlock();
                }

            private:
                Mutex* const mu_;
                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MutexLock);
            };

            // TODO(kenton):  Implement these?  Hard to implement portably.
            typedef MutexLock ReaderMutexLock;
            typedef MutexLock WriterMutexLock;

            // MutexLockMaybe is like MutexLock, but is a no-op when mu is nullptr.
            class PROTOBUF_EXPORT MutexLockMaybe
            {
            public:
                explicit MutexLockMaybe(Mutex* mu) :
                    mu_(mu)
                {
                    if (this->mu_ != nullptr)
                    {
                        this->mu_->Lock();
                    }
                }
                ~MutexLockMaybe()
                {
                    if (this->mu_ != nullptr)
                    {
                        this->mu_->Unlock();
                    }
                }

            private:
                Mutex* const mu_;
                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MutexLockMaybe);
            };

#if defined(GOOGLE_PROTOBUF_NO_THREADLOCAL)
            template<typename T>
            class ThreadLocalStorage
            {
            public:
                ThreadLocalStorage()
                {
                    pthread_key_create(&key_, &ThreadLocalStorage::Delete);
                }
                ~ThreadLocalStorage()
                {
                    pthread_key_delete(key_);
                }
                T* Get()
                {
                    T* result = static_cast<T*>(pthread_getspecific(key_));
                    if (result == nullptr)
                    {
                        result = new T();
                        pthread_setspecific(key_, result);
                    }
                    return result;
                }

            private:
                static void Delete(void* value)
                {
                    delete static_cast<T*>(value);
                }
                pthread_key_t key_;

                GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ThreadLocalStorage);
            };
#endif

        }  // namespace internal

        // We made these internal so that they would show up as such in the docs,
        // but we don't want to stick "internal::" in front of them everywhere.
        using internal::Mutex;
        using internal::MutexLock;
        using internal::MutexLockMaybe;
        using internal::ReaderMutexLock;
        using internal::WriterMutexLock;

    }  // namespace protobuf
}  // namespace google

#undef GOOGLE_PROTOBUF_ACQUIRE
#undef GOOGLE_PROTOBUF_RELEASE

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_STUBS_MUTEX_H_