_HEAP_USERDATA_HEADER

//0x20 bytes (sizeof) struct _HEAP_USERDATA_HEADER { union { struct _SINGLE_LIST_ENTRY SFreeListEntry; //0x0 struct _HEAP_SUBSEGMENT* SubSegment; //0x0 }; VOID* HeapHandle; //0x8 ULONGLONG SizeIndex; //0x10 ULONGLONG Signature; //0x18 };