PoolResource

template<
    std::size_t MAX_BLOCK_SIZE_BYTES,
    std::size_t ALIGN_BYTES>
class PoolResource final

Description

* Owns the allocated memory and frees it on destruction, even when deallocate has not been called on the allocated blocks.

* Consists of a number of pools, each one for a different block size. Each pool holds blocks of uniform size in a freelist.

* Exhausting memory in a freelist causes a new allocation of a fixed size chunk. This chunk is used to carve out blocks.

* Block sizes or alignments that can not be served by the pools are allocated and deallocated by operator new().

PoolResource is not thread-safe. It is intended to be used by PoolAllocator.

An example: If you create a PoolResource<128, 8>(262144) and perform a bunch of allocations and deallocate 2 blocks with size 8 bytes, and 3 blocks with size 16, the members will look like this:

m_free_lists m_allocated_chunks ┌───┐ ┌───┐ ┌────────────-------──────┐ │ │ blocks │ ├─►│ 262144 B │ │ │ ┌─────┐ ┌─────┐ └─┬─┘ └────────────-------──────┘ │ 1 ├─►│ 8 B ├─►│ 8 B │ │ │ │ └─────┘ └─────┘ : │ │ │ │ │ ┌─────┐ ┌─────┐ ┌─────┐ ▼ │ 2 ├─►│16 B ├─►│16 B ├─►│16 B │ ┌───┐ ┌─────────────────────────┐ │ │ └─────┘ └─────┘ └─────┘ │ ├─►│ ▲ │ ▲ │ │ └───┘ └──────────┬──────────────┘ │ │ . │ │ m_available_memory_end │ . │ m_available_memory_it │ . │ │ │ │ │ │16 │ └───┘

Here m_free_lists[1]holds the 2 blocks of size 8 bytes, and m_free_lists[2] holds the 3 blocks of size 16. The blocks came from the data stored in the m_allocated_chunks list. Each chunk has bytes 262144. The last chunk has still some memory available for the blocks, and when m_available_memory_it is at the end, a new chunk will be allocated and added to the list.