typedef struct _RTL_ATOM_TABLE
{
     ULONG Signature;
     RTL_CRITICAL_SECTION CriticalSection;
     RTL_HANDLE_TABLE RtlHandleTable;
     ULONG NumberOfBuckets;
     PRTL_ATOM_TABLE_ENTRY Buckets[1];
} RTL_ATOM_TABLE, *PRTL_ATOM_TABLE;

Windows Vista Kernel Structures