typedef struct _HEAP_SUBSEGMENT
{
    HEAP_LOCAL_SEGMENT_INFO *LocalInfo;
    HEAP_USERDATA_HEADER *UserBlocks;
    INTERLOCK_SEQ AggregateExchg;
    union
    {
        struct
        {
            unsigned short BlockSize;
            unsigned short Flags;
            unsigned short BlockCount;
            unsigned char SizeIndex;
            unsigned char AffinityIndex;
        };
        unsigned long Alignment[2];
    };
    SINGLE_LIST_ENTRY SFreeListEntry;
    volatile unsigned long Lock;
} HEAP_SUBSEGMENT, *PHEAP_SUBSEGMENT;