Custom Memory Allocator – Arma 2

Since Arma 2 Operation Arrowhead build 85869 (1.60 beta) it is possible to provide custom memory allocators for the game. The allocator is a dll placed in dll directory located next to the game executable.

DLL Interface

The dll interface is as follows:

extern "C" {
  __declspec(dllexport) size_t __stdcall MemTotalCommitted();         // _MemTotalCommitted@0
  __declspec(dllexport) size_t __stdcall MemTotalReserved();          // _MemTotalReserved@0
  __declspec(dllexport) size_t __stdcall MemFlushCache(size_t size);  // _MemFlushCache@4
  __declspec(dllexport) void __stdcall MemFlushCacheAll();            // _MemFlushCacheAll@0
  __declspec(dllexport) size_t __stdcall MemSize(void *mem);          // _MemSize@4
  __declspec(dllexport) void *__stdcall MemAlloc(size_t size);        // _MemAlloc@4
  __declspec(dllexport) void __stdcall MemFree(void *mem);            // _MemFree@4
};

MemTotalCommitted()

Total memory committed by the allocator (should correspond to VirtualAlloc with MEM_COMMIT)

MemTotalReserved()

Total memory reserved by the allocator (should correspond to VirtualAlloc with MEM_RESERVE)

MemFlushCache(size_t size)

Try to flush at least "size" bytes of memory from caches and working areas, return how much memory was flushed. Called by game when memory needs to be trimmed to reduce virtual memory use.

MemFlushCacheAll()

Flush all memory held in caches and working areas. Called by game when memory needs to be trimmed to reduce virtual memory use.

MemSize(void *mem)

Return allocated size of given memory block.

MemAlloc(size_t size)

Allocate at least size bytes of memory, return the allocated memory. If the size is 16 B or more, the memory must be 16 B -aligned, so that it is usable to hold SSE data.

MemFree(void *mem)

Free given memory block.