标准库头文件 <memory_resource>

此头文件是动态内存管理库的一部分。

类
定义于命名空间 `std::pmr`
polymorphic_allocator (C++17)	以 std::memory_resource 构造，支持基于它的运行时多态的分配器 (类模板)
memory_resource (C++17)	一个抽象接口，用于各种封装内存资源的类 (类)
pool_options (C++17)	一组池资源的构造函数选项 (类)
synchronized_pool_resource (C++17)	线程安全的 std::pmr::memory_resource，用于管理具有不同块大小的池中的分配 (类)
unsynchronized_pool_resource (C++17)	线程不安全的 std::pmr::memory_resource，用于管理具有不同块大小的池中的分配 (类)
monotonic_buffer_resource (C++17)	一种特殊用途的 std::pmr::memory_resource，仅在资源被销毁时才释放所分配内存 (类)
函数
定义于命名空间 `std::pmr`
new_delete_resource (C++17)	返回一个静态的程序范围 std::pmr::memory_resource，它使用全局 operator new 与 operator delete 分配和解分配内存 (函数)
null_memory_resource (C++17)	返回一个不进行任何分配的静态 std::pmr::memory_resource (函数)
get_default_resource (C++17)	获取缺省 std::pmr::memory_resource (函数)
set_default_resource (C++17)	设置缺省 std::pmr::memory_resource (函数)

概要

namespace std::pmr {
  // 类 memory_resource
  class memory_resource;
 
  bool operator==(const memory_resource& a, const memory_resource& b) noexcept;
 
  // 类模板 polymorphic_allocator
  template<class Tp> class polymorphic_allocator;
 
  template<class T1, class T2>
    bool operator==(const polymorphic_allocator<T1>& a,
                    const polymorphic_allocator<T2>& b) noexcept;
 
  // 全局内存资源
  memory_resource* new_delete_resource() noexcept;
  memory_resource* null_memory_resource() noexcept;
  memory_resource* set_default_resource(memory_resource* r) noexcept;
  memory_resource* get_default_resource() noexcept;
 
  // 池资源类
  struct pool_options;
  class synchronized_pool_resource;
  class unsynchronized_pool_resource;
  class monotonic_buffer_resource;
}

类 std::pmr::memory_resource

namespace std::pmr {
  class memory_resource {
    static constexpr size_t max_align = alignof(max_align_t);   // 仅用于阐释
 
  public:
    memory_resource() = default;
    memory_resource(const memory_resource&) = default;
    virtual ~memory_resource();
 
    memory_resource& operator=(const memory_resource&) = default;
 
    [[nodiscard]] void* allocate(size_t bytes, size_t alignment = max_align);
    void deallocate(void* p, size_t bytes, size_t alignment = max_align);
 
    bool is_equal(const memory_resource& other) const noexcept;
 
  private:
    virtual void* do_allocate(size_t bytes, size_t alignment) = 0;
    virtual void do_deallocate(void* p, size_t bytes, size_t alignment) = 0;
 
    virtual bool do_is_equal(const memory_resource& other) const noexcept = 0;
  };
}

类模板 std::pmr::polymorphic_allocator

namespace std::pmr {
  template<class Tp = byte> class polymorphic_allocator {
    memory_resource* memory_rsrc;       // 仅用于阐释
 
  public:
    using value_type = Tp;
 
    // 构造函数
    polymorphic_allocator() noexcept;
    polymorphic_allocator(memory_resource* r);
 
    polymorphic_allocator(const polymorphic_allocator& other) = default;
 
    template<class U>
      polymorphic_allocator(const polymorphic_allocator<U>& other) noexcept;
 
    polymorphic_allocator& operator=(const polymorphic_allocator&) = delete;
 
    // 成员函数
    [[nodiscard]] Tp* allocate(size_t n);
    void deallocate(Tp* p, size_t n);
 
    [[nodiscard]] void* allocate_bytes(size_t nbytes,
                                       size_t alignment = alignof(max_align_t));
    void deallocate_bytes(void* p, size_t nbytes, size_t alignment = alignof(max_align_t));
    template<class T> [[nodiscard]] T* allocate_object(size_t n = 1);
    template<class T> void deallocate_object(T* p, size_t n = 1);
    template<class T, class... CtorArgs>
      [[nodiscard]] T* new_object(CtorArgs&&... ctor_args);
    template<class T> void delete_object(T* p);
 
    template<class T, class... Args>
      void construct(T* p, Args&&... args);
 
    template<class T>
      void destroy(T* p);
 
    polymorphic_allocator select_on_container_copy_construction() const;
 
    memory_resource* resource() const;
  };
}

类 std::pmr::pool_options

namespace std::pmr {
  struct pool_options {
    size_t max_blocks_per_chunk = 0;
    size_t largest_required_pool_block = 0;
  };
}

类 std::pmr::synchronized_pool_resource

namespace std::pmr {
  class synchronized_pool_resource : public memory_resource {
  public:
    synchronized_pool_resource(const pool_options& opts, memory_resource* upstream);
 
    synchronized_pool_resource()
        : synchronized_pool_resource(pool_options(), get_default_resource()) {}
    explicit synchronized_pool_resource(memory_resource* upstream)
        : synchronized_pool_resource(pool_options(), upstream) {}
    explicit synchronized_pool_resource(const pool_options& opts)
        : synchronized_pool_resource(opts, get_default_resource()) {}
 
    synchronized_pool_resource(const synchronized_pool_resource&) = delete;
    virtual ~synchronized_pool_resource();
 
    synchronized_pool_resource& operator=(const synchronized_pool_resource&) = delete;
 
    void release();
    memory_resource* upstream_resource() const;
    pool_options options() const;
 
  protected:
    void* do_allocate(size_t bytes, size_t alignment) override;
    void do_deallocate(void* p, size_t bytes, size_t alignment) override;
 
    bool do_is_equal(const memory_resource& other) const noexcept override;
  };
}

类 std::pmr::unsynchronized_pool_resource

namespace std::pmr {
  class unsynchronized_pool_resource : public memory_resource {
  public:
    unsynchronized_pool_resource(const pool_options& opts, memory_resource* upstream);
 
    unsynchronized_pool_resource()
        : unsynchronized_pool_resource(pool_options(), get_default_resource()) {}
    explicit unsynchronized_pool_resource(memory_resource* upstream)
        : unsynchronized_pool_resource(pool_options(), upstream) {}
    explicit unsynchronized_pool_resource(const pool_options& opts)
        : unsynchronized_pool_resource(opts, get_default_resource()) {}
 
    unsynchronized_pool_resource(const unsynchronized_pool_resource&) = delete;
    virtual ~unsynchronized_pool_resource();
 
    unsynchronized_pool_resource& operator=(const unsynchronized_pool_resource&) = delete;
 
    void release();
    memory_resource* upstream_resource() const;
    pool_options options() const;
 
  protected:
    void* do_allocate(size_t bytes, size_t alignment) override;
    void do_deallocate(void* p, size_t bytes, size_t alignment) override;
 
    bool do_is_equal(const memory_resource& other) const noexcept override;
  };
}

类 std::pmr::monotonic_buffer_resource

namespace std::pmr {
  class monotonic_buffer_resource : public memory_resource {
    memory_resource* upstream_rsrc;     // 仅用于阐释
    void* current_buffer;               // 仅用于阐释
    size_t next_buffer_size;            // 仅用于阐释
 
  public:
    explicit monotonic_buffer_resource(memory_resource* upstream);
    monotonic_buffer_resource(size_t initial_size, memory_resource* upstream);
    monotonic_buffer_resource(void* buffer, size_t buffer_size, memory_resource* upstream);
 
    monotonic_buffer_resource()
      : monotonic_buffer_resource(get_default_resource()) {}
    explicit monotonic_buffer_resource(size_t initial_size)
      : monotonic_buffer_resource(initial_size, get_default_resource()) {}
    monotonic_buffer_resource(void* buffer, size_t buffer_size)
      : monotonic_buffer_resource(buffer, buffer_size, get_default_resource()) {}
 
    monotonic_buffer_resource(const monotonic_buffer_resource&) = delete;
 
    virtual ~monotonic_buffer_resource();
 
    monotonic_buffer_resource& operator=(const monotonic_buffer_resource&) = delete;
 
    void release();
    memory_resource* upstream_resource() const;
 
  protected:
    void* do_allocate(size_t bytes, size_t alignment) override;
    void do_deallocate(void* p, size_t bytes, size_t alignment) override;
 
    bool do_is_equal(const memory_resource& other) const noexcept override;
  };
}

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