标准库头文件 <memory_resource>

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此头文件是动态内存管理库的一部分。

类

定义于命名空间 `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 `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;
  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;
  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

class memory_resource {
  static constexpr size_t max_align = alignof(max_align_t); // 进用于阐释
public:
  virtual ~memory_resource();
  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

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& rhs) = 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

struct pool_options {
  size_t max_blocks_per_chunk = 0;
  size_t largest_required_pool_block = 0;
};

类 std::pmr::synchronized_pool_resource

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

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

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;
};