Memory Pool Allocation

This functionality provides fixed-size memory allocation for message payloads using free-list pools with multi-pool fallback.

Static View

The following software units are involved in memory pool allocation:

  • Memory Pool Management Unit: Manages multiple pools with different block sizes

    (see Memory Pool Management for its class diagram)

  • Message Management Unit: Requests memory for message payloads

' ******************************************************************************* ' Copyright (c) 2026 BMW AG ' ' This program and the accompanying materials are made available under the ' terms of the Apache License Version 2.0 which is available at ' https://www.apache.org/licenses/LICENSE-2.0 ' ' SPDX-License-Identifier: Apache-2.0 ' ******************************************************************************* @startuml package "Memory Pool Allocation" as memory_pool_allocation_flow { component "Data Structures" as memory_pool_allocation_data_structures { component "Message Management" as memory_pool_allocation_message_management component "Memory Pool Management" as memory_pool_allocation_memory_pool_management } interface "Allocator Requests" as memory_pool_allocation_allocator_requests memory_pool_allocation_message_management -( memory_pool_allocation_allocator_requests memory_pool_allocation_memory_pool_management )-d- memory_pool_allocation_allocator_requests } @enduml

Memory pool allocation component view

Notes:

  • Aggregator routes requests to the appropriate pool based on size.

  • Falls back to larger pools if smaller ones are exhausted.

  • Each pool uses a free-list with pNext_chunk pointer chaining for fast allocation.

  • Each free chunk contains a pointer to the next free chunk (or nullptr if last).

  • Allocation and deallocation are constant-time, O(1).

Dynamic View

The dynamic view illustrates memory allocation with pool selection and fallback.

Allocate

' ******************************************************************************* ' Copyright (c) 2026 BMW AG ' ' This program and the accompanying materials are made available under the ' terms of the Apache License Version 2.0 which is available at ' https://www.apache.org/licenses/LICENSE-2.0 ' ' SPDX-License-Identifier: Apache-2.0 ' ******************************************************************************* @startuml hide footbox participant "Message Management" as message_management_unit participant "Memory Pool Management" as memory_pool_management_unit activate message_management_unit activate memory_pool_management_unit message_management_unit -> memory_pool_management_unit : allocate(requestedSize=48) memory_pool_management_unit -> memory_pool_management_unit : determine best pool (size <= 64) memory_pool_management_unit -> memory_pool_management_unit : allocate() from Pool<64> alt Pool<64> has free block memory_pool_management_unit -> memory_pool_management_unit : get pNext_chunk pointer memory_pool_management_unit -> memory_pool_management_unit : update pNext_chunk from freed chunk's next pointer memory_pool_management_unit -> memory_pool_management_unit : mark chunk as allocated memory_pool_management_unit --> message_management_unit : pointer else Pool<64> is full memory_pool_management_unit -> memory_pool_management_unit : allocate() from Pool<256> [fallback] alt Pool<256> has free block memory_pool_management_unit -> memory_pool_management_unit : get pNext_chunk pointer memory_pool_management_unit -> memory_pool_management_unit : update pNext_chunk from freed chunk's next pointer memory_pool_management_unit -> memory_pool_management_unit : mark chunk as allocated memory_pool_management_unit --> message_management_unit : pointer else all pools are full memory_pool_management_unit --> message_management_unit : nullptr end end message_management_unit -> message_management_unit : wrap pointer result as HRESULT note over message_management_unit : MessagePayloadBuilder reports HRESULT::Ok or CannotAllocatePayload. deactivate message_management_unit deactivate memory_pool_management_unit @enduml

Memory pool allocation sequence

Deallocate

' ******************************************************************************* ' Copyright (c) 2026 BMW AG ' ' This program and the accompanying materials are made available under the ' terms of the Apache License Version 2.0 which is available at ' https://www.apache.org/licenses/LICENSE-2.0 ' ' SPDX-License-Identifier: Apache-2.0 ' ******************************************************************************* @startuml hide footbox participant "Message Management" as message_management_unit participant "Memory Pool Management" as memory_pool_management_unit activate message_management_unit activate memory_pool_management_unit message_management_unit -> memory_pool_management_unit : deallocate(pointer) memory_pool_management_unit -> memory_pool_management_unit : determine pool from pointer address memory_pool_management_unit -> memory_pool_management_unit : deallocate(pointer) in Pool<64> memory_pool_management_unit -> memory_pool_management_unit : write previous pNext_chunk to freed chunk memory_pool_management_unit -> memory_pool_management_unit : update pNext_chunk to point to freed chunk memory_pool_management_unit -> memory_pool_management_unit : mark chunk as free memory_pool_management_unit --> message_management_unit : HRESULT::Ok note over memory_pool_management_unit : Chunk freed and added to the free-list. deactivate message_management_unit deactivate memory_pool_management_unit @enduml

Memory pool deallocation sequence