Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the develop branch, built from commit c5994560ca.
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Class memory_resource

boost::container::pmr::memory_resource

Synopsis

// In header: <boost/container/pmr/memory_resource.hpp>


class memory_resource {
public:
  // construct/copy/destruct
  ~memory_resource();

  // public member functions
  void * allocate(std::size_t, std::size_t = max_align);
  void deallocate(void *, std::size_t, std::size_t = max_align);
  bool is_equal(const memory_resource &) const noexcept;

  // friend functions
  friend bool operator==(const memory_resource &, const memory_resource &) noexcept;
  friend bool operator!=(const memory_resource &, const memory_resource &) noexcept;

  // protected member functions
  virtual void * do_allocate(std::size_t, std::size_t) = 0;
  virtual void do_deallocate(void *, std::size_t, std::size_t) = 0;
  virtual bool do_is_equal(const memory_resource &) const = 0;

  // public data members
  static constexpr std::size_t max_align;
};

Description

The memory_resource class is an abstract interface to an unbounded set of classes encapsulating memory resources.

memory_resource public construct/copy/destruct

  1. ~memory_resource();

    Effects: Destroys this memory_resource.

memory_resource public member functions

  1. void * allocate(std::size_t bytes, std::size_t alignment = max_align);

    Effects: Equivalent to return do_allocate(bytes, alignment);

  2. void deallocate(void * p, std::size_t bytes, 
                    std::size_t alignment = max_align);

    Effects: Equivalent to return do_deallocate(bytes, alignment);

  3. bool is_equal(const memory_resource & other) const noexcept;

    Effects: Equivalent to return return do_is_equal(other);

memory_resource friend functions

  1. friend bool operator==(const memory_resource & a, const memory_resource & b) noexcept;

    Returns: &a == &b || a.is_equal(b).

  2. friend bool operator!=(const memory_resource & a, const memory_resource & b) noexcept;

    Returns: !(a == b).

memory_resource protected member functions

  1. virtual void * do_allocate(std::size_t bytes, std::size_t alignment) = 0;

    Requires: Alignment shall be a power of two.

    Returns: A derived class shall implement this function to return a pointer to allocated storage with a size of at least bytes. The returned storage is aligned to the specified alignment, if such alignment is supported; otherwise it is aligned to max_align.

    Throws: A derived class implementation shall throw an appropriate exception if it is unable to allocate memory with the requested size and alignment.

  2. virtual void 
    do_deallocate(void * p, std::size_t bytes, std::size_t alignment) = 0;

    Requires: p shall have been returned from a prior call to allocate(bytes, alignment) on a memory resource equal to *this, and the storage at p shall not yet have been deallocated.

    Effects: A derived class shall implement this function to dispose of allocated storage.

    Throws: Nothing.

  3. virtual bool do_is_equal(const memory_resource & other) const = 0;

    Returns: A derived class shall implement this function to return true if memory allocated from this can be deallocated from other and vice-versa; otherwise it shall return false. [Note: The most-derived type of other might not match the type of this. For a derived class, D, a typical implementation of this function will compute dynamic_cast<const D*>(&other) and go no further (i.e., return false) if it returns nullptr. - end note].


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