OUT: Pointer to memory where the transform expression will be copied
IN: Number of bytes of the transform expression to copy to
H5P_GET_DATA_TRANSFORM retrieves the data transform expression previously set in the dataset transfer property list plist_id by H5P_SET_DATA_TRANSFORM.
H5P_GET_DATA_TRANSFORM can be used to both retrieve the transform expression and to query its size.
If expression is non-NULL, up to size bytes of the data transform expression are written to the buffer. If expression is NULL, size is ignored and the function does not write anything to the buffer. The function always returns the size of the data transform expression.
If 0 is returned for the size of the expression, no data transform expression exists for the property list.
If an error occurs, the buffer pointed to by expression is unchanged and the function returns a negative value.