# 标准库头文件 <mutex>

< cpp‎ | header

此头文件是线程支持库的一部分。

### 类
mutex (C++11) | 提供基本互斥设施 (类)
timed_mutex (C++11) | 提供互斥设施，实现有时限锁定 (类)
recursive_mutex (C++11) | 提供能被同一线程递归锁定的互斥设施 (类)
recursive_timed_mutex (C++11) | 提供能被同一线程递归锁定的互斥设施，并实现有时限锁定 (类)
lock_guard (C++11) | 实现严格基于作用域的互斥体所有权包装器 (类模板)
unique_lock (C++11) | 实现可移动的互斥体所有权包装器 (类模板)
scoped_lock (C++17) | 用于多个互斥体的免死锁 RAII 封装器 (类模板)
defer_lock_t try_to_lock_t adopt_lock_t (C++11)(C++11)(C++11) | 用于指定锁定策略的标签类型 (类)
once_flag (C++11) | 确保 `call_once` 只调用函数一次的帮助对象 (类)
### 常量
defer_lock try_to_lock adopt_lock (C++11)(C++11)(C++11) | 用于指定锁定策略的标签常量 (常量)
### 函数
try_lock (C++11) | 试图通过重复调用 `try_lock` 获得互斥体的所有权 (函数模板)
lock (C++11) | 锁定指定的互斥体，若任何一个不可用则阻塞 (函数模板)
call_once (C++11) | 仅调用函数一次，即使从多个线程调用 (函数模板)
std::swap(std::unique_lock) (C++11) | std::swap 对 `unique_lock` 的特化 (函数模板)

### 概要

    namespace std {
      class mutex;
      class recursive_mutex;
      class timed_mutex;
      class recursive_timed_mutex;

      struct defer_lock_t { explicit defer_lock_t() = default; };
      struct try_to_lock_t { explicit try_to_lock_t() = default; };
      struct adopt_lock_t { explicit adopt_lock_t() = default; };

      inline constexpr defer_lock_t  defer_lock { };
      inline constexpr try_to_lock_t try_to_lock { };
      inline constexpr adopt_lock_t  adopt_lock { };

      template<class Mutex> class lock_guard;
      template<class... MutexTypes> class scoped_lock;
      template<class Mutex> class unique_lock;

      template<class Mutex>
        void swap(unique_lock<Mutex>& x, unique_lock<Mutex>& y) noexcept;

      template<class L1, class L2, class... L3> int try_lock(L1&, L2&, L3&...);
      template<class L1, class L2, class... L3> void lock(L1&, L2&, L3&...);

      struct once_flag;

      template<class Callable, class... Args>
        void call_once(once_flag& flag, Callable&& func, Args&&... args);
    }

#### 类 std::mutex

    namespace std {
      class mutex {
      public:
        constexpr mutex() noexcept;
        ~mutex();

        mutex(const mutex&) = delete;
        mutex& operator=(const mutex&) = delete;

        void lock();
        bool try_lock();
        void unlock();

        using native_handle_type = /* 由实现定义 */;
        native_handle_type native_handle();
      };
    }

#### 类 std::recursive_mutex

    namespace std {
      class recursive_mutex {
      public:
        recursive_mutex();
        ~recursive_mutex();

        recursive_mutex(const recursive_mutex&) = delete;
        recursive_mutex& operator=(const recursive_mutex&) = delete;

        void lock();
        bool try_lock() noexcept;
        void unlock();

        using native_handle_type = /* 由实现定义 */;
        native_handle_type native_handle();
      };
    }

#### 类 std::timed_mutex

    namespace std {
      class timed_mutex {
      public:
        timed_mutex();
        ~timed_mutex();

        timed_mutex(const timed_mutex&) = delete;
        timed_mutex& operator=(const timed_mutex&) = delete;

        void lock();    // 阻塞
        bool try_lock();
        template<class Rep, class Period>
          bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
        template<class Clock, class Duration>
          bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
        void unlock();

        using native_handle_type = /* 由实现定义 */;
        native_handle_type native_handle();
      };
    }

#### 类 std::recursive_timed_mutex

    namespace std {
      class recursive_timed_mutex {
      public:
        recursive_timed_mutex();
        ~recursive_timed_mutex();

        recursive_timed_mutex(const recursive_timed_mutex&) = delete;
        recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;

        void lock();    // 阻塞
        bool try_lock() noexcept;
        template<class Rep, class Period>
          bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
        template<class Clock, class Duration>
          bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
        void unlock();

        using native_handle_type = /* 由实现定义 */;
        native_handle_type native_handle();
      };
    }

#### 类模板 std::lock_guard

    namespace std {
      template<class Mutex>
      class lock_guard {
      public:
        using mutex_type = Mutex;

        explicit lock_guard(mutex_type& m);
        lock_guard(mutex_type& m, adopt_lock_t);
        ~lock_guard();

        lock_guard(const lock_guard&) = delete;
        lock_guard& operator=(const lock_guard&) = delete;

      private:
        mutex_type& pm;             // 仅用于阐释
      };
    }

#### 类模板 std::scoped_lock

    namespace std {
      template<class... MutexTypes>
      class scoped_lock {
      public:
        using mutex_type = Mutex;   // 若 MutexTypes... 仅由单个类型 Mutex 组成

        explicit scoped_lock(MutexTypes&... m);
        explicit scoped_lock(adopt_lock_t, MutexTypes&... m);
        ~scoped_lock();

        scoped_lock(const scoped_lock&) = delete;
        scoped_lock& operator=(const scoped_lock&) = delete;

      private:
        tuple<MutexTypes&...> pm;   // 仅用于阐释
      };
    }

#### 类模板 std::unique_lock

    namespace std {
      template<class Mutex>
      class unique_lock {
      public:
        using mutex_type = Mutex;

        // 构造/复制/销毁
        unique_lock() noexcept;
        explicit unique_lock(mutex_type& m);
        unique_lock(mutex_type& m, defer_lock_t) noexcept;
        unique_lock(mutex_type& m, try_to_lock_t);
        unique_lock(mutex_type& m, adopt_lock_t);
        template<class Clock, class Duration>
          unique_lock(mutex_type& m, const chrono::time_point<Clock, Duration>& abs_time);
        template<class Rep, class Period>
          unique_lock(mutex_type& m, const chrono::duration<Rep, Period>& rel_time);
        ~unique_lock();

        unique_lock(const unique_lock&) = delete;
        unique_lock& operator=(const unique_lock&) = delete;

        unique_lock(unique_lock&& u) noexcept;
        unique_lock& operator=(unique_lock&& u);

        // 锁定
        void lock();
        bool try_lock();

        template<class Rep, class Period>
          bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
        template<class Clock, class Duration>
          bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);

        void unlock();

        // 修改器
        void swap(unique_lock& u) noexcept;
        mutex_type* release() noexcept;

        // 观察器
        bool owns_lock() const noexcept;
        explicit operator bool () const noexcept;
        mutex_type* mutex() const noexcept;

      private:
        mutex_type* pm;             // 仅用于阐释
        bool owns;                  // 仅用于阐释
      };

      template<class Mutex>
        void swap(unique_lock<Mutex>& x, unique_lock<Mutex>& y) noexcept;
    }

#### 类 std::once_flag

    struct once_flag {
        constexpr once_flag() noexcept;
        once_flag(const once_flag&) = delete;
        once_flag& operator=(const once_flag&) = delete;
    };