H5O_layout_t        layout;         /* data layout                  */
    hbool_t             checked_filters;/* TRUE if dataset passes can_apply check */
    /* Cache some frequently accessed values from the DCPL */
    H5O_efl_t           efl;            /* External file list information */
    H5D_alloc_time_t    alloc_time;     /* Dataset allocation time      */
    H5D_fill_time_t fill_time;  /* Dataset fill value writing time */
    H5O_fill_t          fill;           /* Dataset fill value information */
    /* Buffered/cached information for types of raw data storage*/
    union {
    struct {
        H5D_rdcdc_t     contig;         /* Information about contiguous data */
                                        /* (Note that the "contig" cache
                                         * information can be used by a chunked
                                         * dataset in certain circumstances)
                                         */
        H5D_rdcc_t      chunk;          /* Information about chunked data */
    }cache;
};
/* Enumerated type for allocating dataset's storage */
typedef enum {
    H5D_ALLOC_CREATE,           /* Dataset is being created */
    H5D_ALLOC_OPEN,             /* Dataset is being opened */
    H5D_ALLOC_EXTEND,           /* Dataset's dataspace is being extended */
    H5D_ALLOC_WRITE             /* Dataset is being extended */