std::pmr_monotonic_buffer_resource - Man Page

A memory resource that allocates from a fixed-size buffer.

Synopsis

#include <memory_resource>

Inherits std::pmr::memory_resource.

monotonic_buffer_resource (const monotonic_buffer_resource &)=delete
monotonic_buffer_resource (memory_resource *__upstream) noexcept
monotonic_buffer_resource (size_t __initial_size) noexcept
monotonic_buffer_resource (size_t __initial_size, memory_resource *__upstream) noexcept
monotonic_buffer_resource (void *__buffer, size_t __buffer_size) noexcept
monotonic_buffer_resource (void *__buffer, size_t __buffer_size, memory_resource *__upstream) noexcept
void * allocate (size_t __bytes, size_t __alignment=_S_max_align)
void deallocate (void *__p, size_t __bytes, size_t __alignment=_S_max_align)
bool is_equal (const memory_resource &__other) const noexcept
monotonic_buffer_resource & operator= (const monotonic_buffer_resource &)=delete
void release () noexcept
memory_resource * upstream_resource () const noexcept

Protected Member Functions

void * do_allocate (size_t __bytes, size_t __alignment) override
void do_deallocate (void *, size_t, size_t) override
bool do_is_equal (const memory_resource &__other) const noexcept override

Detailed Description

A memory resource that allocates from a fixed-size buffer.

The main feature of a pmr::monotonic_buffer_resource is that its do_deallocate does nothing. This makes it very fast because there is no need to manage a free list, and every allocation simply returns a new block of memory, rather than searching for a suitably-sized free block. Because deallocating is a no-op, the amount of memory used by the resource only grows until release() (or the destructor) is called to return all memory to upstream.

A monotonic_buffer_resource can be initialized with a buffer that will be used to satisfy all allocation requests, until the buffer is full. After that a new buffer will be allocated from the upstream resource. By using a stack buffer and pmr::null_memory_resource() as the upstream you can get a memory resource that only uses the stack and never dynamically allocates.