typedef struct _RTL_AVL_TABLE
{
     RTL_BALANCED_LINKS BalancedRoot;
     PVOID OrderedPointer;
     ULONG WhichOrderedElement;
     ULONG NumberGenericTableElements;
     ULONG DepthOfTree;
     PRTL_BALANCED_LINKS RestartKey;
     ULONG DeleteCount;
     PRTL_GENERIC_COMPARE_RESULTS CompareRoutine;
     PVOID * AllocateRoutine;
     PVOID FreeRoutine;
     PVOID TableContext;
} RTL_AVL_TABLE, *PRTL_AVL_TABLE;

Windows Vista Kernel Structures