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/* Type of memory actions */
enum {
        UMEM_ACT_NOOP                   = 0,
        /** copy appended payload to specified storage address */
        UMEM_ACT_COPY,
        /** copy payload addressed by @ptr to specified storage address */
        UMEM_ACT_COPY_PTR,
        /** assign 8/16/32/64 bits integer to specified storage address */
        UMEM_ACT_COPY_INTASSIGN,
        /** move specified bytes from source address to destination address */
        UMEM_ACT_MOVE,
        /** memset a region with specified value */
        UMEM_ACT_SET,
        /** set the specified bit in bitmap */
        UMEM_ACT_SET_BITS,
        /** unset the specified bit in bitmap */
        UMEM_ACT_CLR_BITS,
        /** it's checksum of the specified address */
        UMEM_ACT_CSUM,
};

/**
 * Memory operations for redo/undo.
 * 16 bytes for bit operation (set/clr) and integer assignment, 32+ bytes for
 * other operations.
 */
struct umem_action {
        uint16_t                        ac_opc;
        union {
                struct {
                        uint16uint64_t                numaddr;
                        uint32uint64_t                possize;
                        uint64uint8_t                 addrpayload[0];
                } ac_op_bits;
    copy;      /**< copy payload from @payload to @addr */
                struct {
                        uint64_t                addr;
                        uint64_t                size;
                        uint8uint64_t                 valptr;
                } ac_copy_set;
   ptr;  /**< copy payload from @ptr to @addr */
                struct {
                        uint64uint16_t                srcsize;
                        uint64uint32_t                dstval;
                        uint64_t                sizeaddr;
                } ac_move;assign;    /**< assign integer to @addr, int64 should use ac_copy */
                struct {
                        uint64uint16_t                addrnum;
                        uint64uint32_t                sizepos;
                        uint8uint64_t                 payload[0]bmap;
                } ac_copyop_bits;   /**< set or clear the @pos bit in bitmap @bmap */
                struct {
                        uint64uint16_t                addrval;
                        uint64uint32_t                valsize;
                        uint8uint64_t                 size; /* int8/16/32/64 */addr;
                } ac_set;       /**< memset(addr, val, size) */
                struct {
                 } ac_copy_int;
        uint16_t               struct {pad16;
                        uint64uint32_t                addrsize;
                        uint64_t                sizesrc;
                        uint64_t                ptrdst;
                } ac_copy_ptrmove;      /**< memmove(dst, size src) */
                struct {
                        uint64uint16_t                addrcsum_sz;
                        uint32_t                size;
                        uint16uint64_t                csum_szaddr;
                        uint8_t                 csum[0];
                } ac_csum;      /**< it is checksum of data stored in @addr */
        };
};