typedef struct _POOL_HEADER
{
    union
    {
        struct
        {
            unsigned long PreviousSize : 8;
            unsigned long PoolIndex : 8;
            unsigned long BlockSize : 8;
            unsigned long PoolType : 8;
        };
        unsigned long Ulong1;
    };
    unsigned long PoolTag;
    union
    {
        EPROCESS *ProcessBilled;
        struct
        {
            unsigned short AllocatorBackTraceIndex;
            unsigned short PoolTagHash;
        };
    };
} POOL_HEADER, *PPOOL_HEADER;