#############################################################################
##
## Copyright 2016 Novartis Institutes for BioMedical Research Inc.
## Licensed under the Apache License, Version 2.0 (the "License");
## you may not use this file except in compliance with the License.
## You may obtain a copy of the License at
##
## http://www.apache.org/licenses/LICENSE-2.0
##
## Unless required by applicable law or agreed to in writing, software
## distributed under the License is distributed on an "AS IS" BASIS,
## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
## See the License for the specific language governing permissions and
## limitations under the License.
##
#############################################################################








##' Class for representing HDF5 spaces
##' 
##' This class represents \code{Spaces} in HDF5. These are mostly useful to define the
##' dimensions of a dataset as well as the maximum dimensions to which it can grow. By default, the
##' maximum dimension is equal to the initial dimension. If you want the array to be able to grow arbitrarily
##' large in one dimension, set the maximum dimension for this index to \code{Inf}. See the examples below
##' for code how to do this.
##'
##' @docType class
##' @importFrom R6 R6Class
##' @return Object of class \code{\link{H5S}}. 
##' @author Holger Hoefling
##'
##' @examples
##' h5s_fixed <- H5S$new("simple", dims=c(5, 2))
##' h5s_fixed
##' 
##' h5s_variable <- H5S$new("simple", dims=c(5,2), maxdims=c(Inf,2))
##' h5s_variable
##' h5s_variable$set_extent_simple(c(10,2), c(Inf, 2))
##' h5s_variable
##' 
##' # now select a subset of points
##' # argument evaluation has a heuristic; here it chooses point selection
##' h5s_variable[c(1, 3, 8), 1]
##' h5s_variable$get_select_type()
##' h5s_variable$get_select_elem_pointlist()
##' 
##' # and a hyperslab (chosen by the argument heuristic)
##' h5s_variable[2:7, 1:2]
##' h5s_variable$get_select_type()
##' h5s_variable$get_select_hyper_blocklist()
##' @export
H5S <- R6Class("H5S",
               inherit=H5RefClass,
               public=list(
                   initialize=function(type=c("simple", "scalar", "null"), dims=NULL, maxdims=dims, decode_buf=NULL, id=NULL) {
                       "Create a new HDF5-space. This can be done by either specifying a space with appropriate dimensions or by"
                       "decoding a character string that represents an encoded space"
                       "@param type Either a \\code{simple} space, for which \\code{dims} and \\code{maxdims} have to be given"
                       "or a \\code{scalar} or \\code{null} space. See the HDF5 user guide on spaces to explain the differences."
                       "@param dims The dimension of the space in case it is of type \\code{simple}"
                       "@param maxdims The maximal dimensions of the space"
                       "@param decode_buf The character string that holds the encoded representation of a space"
                       "@param id An existing HDF5 id; internal use only"
                       if(is.null(id)) {
                           if(!is.null(decode_buf)) {
                               id <- .Call("R_H5Sdecode", decode_buf, PACKAGE = "hdf5r")$return_val
                           }
                           else {
                               type <- match.arg(type)
                               type <- switch(type, scalar=h5const$H5S_SCALAR, simple=h5const$H5S_SIMPLE, null=h5const$H5S_NULL)
                               
                               if(type!=h5const$H5S_SIMPLE ||(type==h5const$H5S_SIMPLE && (is.null(dims) || is.null(maxdims)))) {
                                   id <- .Call("R_H5Screate", type, PACKAGE = "hdf5r")$return_val
                                   if(id < 0) {
                                       stop("Error creating dataspace")
                                   }
                               }
                               else {
                                   if(is.null(dims)) {
                                       stop("dims cannot be null")
                                   }
                                   rank <- length(dims)
                                   if(length(maxdims) > 0 && length(maxdims) != rank) {
                                       stop("maxdims, if it is not NULL, has to be of the same length as dims")
                                   }
                                   id <- .Call("R_H5Screate_simple", rank, rev(dims), rev(maxdims), PACKAGE="hdf5r")$return_val
                                   if(id < 0) {
                                       stop("Error creating simple dataspace")
                                   }
                               }
                           }
                       }
                       super$initialize(id)
                   },
                   copy=function() {
                       "This function implements the HDF5-API function H5Scopy. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_COPY} for details."

                       id <- .Call("R_H5Scopy", self$id, PACKAGE = "hdf5r")$return_val
                       return(H5S$new(id=id))
                   },
                   encode=function() {
                       "This function implements the HDF5-API function H5Sencode. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_ENCODE} for details."

                       ## first retrieve the size of the buffer necessary
                       nalloc <- .Call("R_H5Sencode", self$id, raw(0), numeric(1), FALSE, PACKAGE = "hdf5r")$nalloc
                       ## now get the actual buffer size
                       buf <- raw(nalloc)
                       res <- .Call("R_H5Sencode", self$id, buf, nalloc, FALSE, PACKAGE="hdf5r")
                       herr <- res$return_val
                       if(herr < 0) {
                           stop("Error when encoding the object")
                       }
                       return(res$buf)
                   },
                   is_simple=function() {
                       "This function implements the HDF5-API function H5Sis_simple. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_IS_SIMPLE} for details."

                       res <- .Call("R_H5Sis_simple", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error when trying to see if dataspace is simple")
                       }
                       return(as.logical(res))
                   },
                   get_simple_extent_ndims=function() {
                       "This function implements the HDF5-API function H5Sget_simple_extent_ndims. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SIMPLE_EXTENT_NDIMS} for details."

                       ndims <- .Call("R_H5Sget_simple_extent_ndims", self$id, PACKAGE = "hdf5r")$return_val
                       if(ndims < 0) {
                           stop("Error when retrieving rank of dataspace")
                       }
                       return(ndims)
                   },
                   offset_simple=function(offset) {
                       "This function implements the HDF5-API function H5Soffset_simple. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_OFFSET_SIMPLE} for details."

                       rank <- self$get_simple_extent_ndims()
                       if(length(offset)==0) {
                           offset <- rep(0, rank)
                       }
                       if(length(offset) != rank) {
                           stop(paste("Offset has to be of rank", rank))
                       }
                       res <- .Call("R_H5Soffset_simple", self$id, rev(offset), PACKAGE = "hdf5r")
                       if(res$return_val < 0) {
                           stop("Error when setting offset")
                       }
                       return(invisible(self))
                   },
                   get_simple_extent_dims=function() {
                       "This function implements the HDF5-API function H5Sget_simple_extent_dims. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SIMPLE_EXTENT_DIMS} for details."

                       return(standalone_H5S_get_simple_extent_dims(self$id))
                   },
                   get_simple_extent_npoints=function() {
                       "This function implements the HDF5-API function H5Sget_simple_extent_npoints. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SIMPLE_EXTENT_NPOINTS} for details."

                       res <- .Call("R_H5Sget_simple_extent_npoints", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error trying to get number of points in dataspace")
                       }
                       return(res)
                   },
                   get_simple_extent_type=function() {
                       "This function implements the HDF5-API function H5Sget_simple_extent_type. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SIMPLE_EXTENT_TYPE} for details."

                       return(.Call("R_H5Sget_simple_extent_type", self$id, PACKAGE = "hdf5r")$return_val)
                   },
                   extent_copy=function(h5s_source) {
                       "This function implements the HDF5-API function H5Sextent_copy. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_EXTENT_COPY} for details."

                       if(!inherits(h5s_source, "H5S")) {
                           stop("h5s_source has to be of class H5S")
                       }
                       res <- .Call("R_H5Sextent_copy", self$id, h5s_source$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error copying extent of dataspace")
                       }
                       return(invisible(self))
                   },
                   extent_equal=function(h5s_cmp) {
                       "This function implements the HDF5-API function H5Sextent_equal. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_EXTENT_EQUAL} for details."

                       if(!inherits(h5s_cmp, "H5S")) {
                           stop("h5s_source has to be of class H5S")
                       }
                       res <- .Call("R_H5Sextent_equal", self$id, h5s_cmp$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error copying extent of dataspace")
                       }
                       return(as.logical(res))
                   },
                   set_extent_simple=function(dims, maxdims) {
                       "This function implements the HDF5-API function H5Sset_extent_simple. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SET_EXTENT_SIMPLE} for details."

                       rank <- length(dims)
                       if(rank ==0) {
                           stop("current_size has to be of length > 0")
                       }
                       if(length(maxdims) != rank) {
                           stop(paste("maximum_size has to be of same length as current_size, i.e. ", rank))
                       }
                       if(!all(maxdims >= dims)) {
                           stop("Maximum_size has to be greater or equal to current_size")
                       }
                       res <- .Call("R_H5Sset_extent_simple", self$id, rank, rev(dims), rev(maxdims), PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error setting simple extent")
                       }
                       return(invisible(self))
                   },
                   set_extent_none=function() {
                       "This function implements the HDF5-API function H5Sset_extent_none. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SET_EXTENT_NONE} for details."

                       res <- .Call("R_H5Sset_extent_none", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error setting simple extent")
                       }
                       return(invisible(self))
                   },
                   get_select_type=function() {
                       "This function implements the HDF5-API function H5Sget_select_type. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_TYPE} for details."

                       res <- .Call("R_H5Sget_select_type", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error getting selection type")
                       }
                       return(res)
                   },
                   get_select_npoints=function() {
                       "This function implements the HDF5-API function H5Sget_select_npoints. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_NPOINTS} for details."

                       res <- .Call("R_H5Sget_select_npoints", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error getting number of points in selection")
                       }
                       return(res)
                   },
                   get_select_hyper_nblocks=function() {
                       "This function implements the HDF5-API function H5Sget_select_hyper_nblocks. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_HYPER_NBLOCKS} for details."

                       res <- .Call("R_H5Sget_select_hyper_nblocks", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error getting number of points in selection")
                       }
                       return(res)
                   },
                   get_select_hyper_blocklist=function(startblock=0, numblocks=(self$get_select_hyper_nblocks() - startblock)) {
                       "This function implements the HDF5-API function H5Sget_select_hyper_blocklist. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_HYPER_BLOCKLIST} for details."

                       rank <- self$get_simple_extent_ndims()
                       ## create a buffer; a buffer of double values provides enough space; function will handle
                       ## appropriate conversion
                       res <- .Call("R_H5Sget_select_hyper_blocklist", self$id, startblock, numblocks, request_empty(rank * 2 * numblocks),
                                    PACKAGE = "hdf5r")
                       if(res$return_val < 0) {
                           stop("Error trying to retrieve blocklist")
                       }
                       ## get the buffer, format as array, reverse the dimensions and return
                       buffer <- res$buf
                       dim(buffer) <- c(rank, 2 * numblocks)
                       for(i in seq_len(ncol(buffer))) {
                           buffer[, i] <- rev(buffer[, i])
                       }
                       ## correct for first element 0
                       buffer <- t(buffer) + 1
                       rownames(buffer) <- paste("block", rep(seq_len(numblocks), each=2), rep(c("start", "end"), times=numblocks), sep="_")
                       return(buffer)
                   },
                   get_select_elem_npoints=function() {
                       "This function implements the HDF5-API function H5Sget_select_elem_npoints. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_ELEM_NPOINTS} for details."

                       res <- .Call("R_H5Sget_select_elem_npoints", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error trying to get number of elements in current selection")
                       }
                       return(res)
                   },
                   get_select_elem_pointlist=function(startpoint=0, numpoints=(self$get_select_elem_npoints() - startpoint)) {
                       "This function implements the HDF5-API function H5Sget_select_elem_pointlist. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_ELEM_POINTLIST} for details."

                       rank <- self$get_simple_extent_ndims()
                       ## create a buffer; a buffer of double values provides enough space; function will handle
                       ## appropriate conversion
                       res <- .Call("R_H5Sget_select_elem_pointlist", self$id, startpoint, numpoints, request_empty(rank * numpoints),
                                    PACKAGE = "hdf5r")
                       if(res$return_val < 0) {
                           stop("Error trying to retrieve blocklist")
                       }
                       ## get the buffer, format as array, reverse the dimensions and return
                       buffer <- res$buf
                       dim(buffer) <- c(rank, numpoints)
                       buffer_rev <- buffer
                       for(i in seq_len(rank)) {
                           buffer_rev[i,] <- buffer[rank + 1 - i,]
                       }
                       buffer <- buffer_rev

                       ## correct for first element 0
                       buffer <- t(buffer) + 1
                       return(buffer)
                   },
                   get_select_bounds=function() {
                       "This function implements the HDF5-API function H5Sget_select_bounds. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_GET_SELECT_BOUNDS} for details."

                       rank <- self$get_simple_extent_ndims()
                       start <- integer(rank)
                       end <- integer(rank)
                       res <- .Call("R_H5Sget_select_bounds", self$id, start, end, PACKAGE = "hdf5r")
                       if(res$return_val < 0) {
                           stop("Error trying to get bounding box of selection")
                       }
                       ## correct for first element 0
                       start <- rev(res$start) + 1
                       end <- rev(res$end) + 1
                       return(list(start=start, end=end))
                   },                   
                   select_all=function() {
                       "This function implements the HDF5-API function H5Sselect_all. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SELECT_ALL} for details."

                       res <- .Call("R_H5Sselect_all", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error when selecting all points in dataspace")
                       }
                       return(invisible(self))
                   },
                   select_none=function() {
                       "This function implements the HDF5-API function H5Sselect_none. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SELECT_NONE} for details."

                       res <- .Call("R_H5Sselect_none", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error when reseting selection region")
                       }
                       return(invisible(self))
                   },
                   select_valid=function() {
                       "This function implements the HDF5-API function H5Sselect_valid. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SELECT_VALID} for details."

                       res <- .Call("R_H5Sselect_valid", self$id, PACKAGE = "hdf5r")$return_val
                       if(res < 0) {
                           stop("Error validating selection")
                       }
                       return(as.logical(res))
                   },
                   select_elements=function(coord, op=h5const$H5S_SELECT_SET, byrow=TRUE) {
                       "This function implements the HDF5-API function H5Sselect_elements. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SELECT_ELEMENTS} for details."

                       standalone_H5S_select_elements(self$id, coord=coord, op=op, byrow=byrow)
                       return(invisible(self))

                   },
                   select_hyperslab=function(start, count, stride=NULL, block=NULL, op=h5const$H5S_SELECT_SET) {
                       "This function implements the HDF5-API function H5Sselect_hyperslab. Please see the documentation at \\url{https://portal.hdfgroup.org/display/HDF5/H5S_SELECT_HYPERSLAB} for details."

                       standalone_H5S_select_hyperslab(id=self$id, start=start, count=count, stride=stride, block=block, op=op)
                       return(invisible(self))
                   },
                   subset=function(args, op=h5const$H5S_SELECT_SET, envir=parent.frame()) {
                       "Subsetting the space. This is mainly intended as a helper function for the '[' function, but"
                       "can also be used on its own."
                       "@param args The indices for each dimension to subset given as a list. This makes this easier to use as a programmatic API."
                       "For interactive use we recommend the use of the \\code{[} operator."
                       "@param op The operator to use. Same as for the other HDF5 space selection functions. One of the elements shown in"
                       "\\code{h5const$H5S_seloper_t}"
                       "@param envir The environment in which to evaluate \\code{args}"
                       if(!self$is_simple()) {
                           stop("Dataspace has to be simple for a selection to occur")
                       }
                       simple_extent <- self$get_simple_extent_dims()    
                       ## distinguish between scalar and non-scalar
                       if(simple_extent$rank == 0 && self$get_select_npoint() == 1) {
                           ## is a scalar
                           if(!are_args_scalar(args)) {
                               stop("Scalar dataspace; arguments have to be of length 1 and empty or equal to 1")
                           }
                           ## nothing needs to be done; just fall through to the end
                       }
                       else {
                           reg_eval_res <- args_regularity_evaluation(args=args, ds_dims=simple_extent$dims, envir=envir)
                           ## need to check if maximum dimension in indices are larger than dataset dimensions
                           ## if yes need to throw an error
                           if(any(reg_eval_res$max_dims > simple_extent$dims)) {
                               stop("The following coordinates are outside the dataset dimensions: ",
                                    paste(which(reg_eval_res$max_dims > simple_extent$dims), sep=", "))
                           }
                           selection <- regularity_eval_to_selection(reg_eval_res=reg_eval_res) 
                           apply_selection(space_id=self$id, selection=selection)
                       }
                       return(invisible(self))
                   },
                   print=function(...){
                       "Prints information for the group"
                       "@param ... ignored"
                       
                       is_valid <- self$is_valid
                       
                       print_class_id(self, is_valid)

                       if(is_valid) {
                           if(!self$is_simple()) {
                               ## has to be a NULL space
                               cat("Type: NULL\n")
                           }
                           else {
                               extent_res <- self$get_simple_extent_dims()
                               if(extent_res$rank == 0) {
                                   cat("Type: Scalar\n")
                               }
                               else {
                                   cat("Type: Simple\n")
                                   cat("Dims: ", paste(extent_res$dims, collapse=" x "), "\n", sep="")
                                   cat("Maxdims: ", paste(extent_res$maxdims, collapse=" x "), "\n", sep="")
                               }
                           }
                       }
                       return(invisible(self))
                   }
               ),
               active=list(
                   dims=function() {
                       "Get the dimensions of the space. Return NULL if the space is not simple (i.e. NULL-space) or a length-0 integer if it is a scalar"
                       if(!self$is_simple()) {
                           return(NULL)
                       }
                       return(self$get_simple_extent_dims()$dims)
                   },
                   maxdims=function() {
                       "Get the maximal dimensions of the space.Return NULL if the space is not simple (i.e. NULL-space) or a length-0 integer if it is a scalar"
                       if(!self$is_simple()) {
                           return(NULL)
                       }
                       return(self$get_simple_extent_dims()$maxdims)
                   }
                   ),
               private=list(
                   closeFun=function(id) if(!is.na(id) && is.loaded("R_H5Sclose", PACKAGE="hdf5r")) {
                          invisible(.Call("R_H5Sclose", id, PACKAGE = "hdf5r"))}
                   ),
               cloneable = FALSE
               )

## make 'rank' a copy of get_simple_extent_ndims
H5S$set("active", "rank", H5S$public_methods$get_simple_extent_ndims, overwrite=TRUE)



#' Class for HDF5 default space
#'
#' It inherits all functions of the \code{\link{H5S}}. As this is implemented, closing the id is overridden as this is a special id.
#' @docType class
#' @importFrom R6 R6Class
#' @return Object of class \code{\link[=H5S_ALL]{H5S_ALL}}. 
#' @author Holger Hoefling
#' @keywords internal
#' @seealso \code{\link[=H5S]{H5S}}
H5S_ALL <- R6Class("H5S_ALL",
                       inherit=H5S,
                       public=list(
                           initialize=function(id) {
                               private$pid <- new_id_obj(id)
                               return(self)
                           },
                           print=function(...) {
                               "Just prints that it is the default class"
                               "@param ... ignored"
                               cat("H5S_ALL class\n")
                               return(invisible(self))
                           }
                           ),
                       private=list(
                           closeFun=identity
                           ),
                       cloneable=FALSE
                       )


## some additional functions that either duplicate functionality of the R6 object, but without requiring the
## R6 object. This is intended as a speed improvement

standalone_H5S_get_simple_extent_ndims <- function(id) {
    ndims <- .Call("R_H5Sget_simple_extent_ndims", id, PACKAGE = "hdf5r")$return_val
    if(ndims < 0) {
        stop("Error when retrieving rank of dataspace")
    }
    return(ndims)
}


standalone_H5S_select_elements <- function(id, coord, op=h5const$H5S_SELECT_SET, byrow=TRUE) {
    rank <- standalone_H5S_get_simple_extent_ndims(id)
    
    ## check that coord is an array; is rank=1, also allowed to be a vector
    if(rank==0) {
        stop("Dataspace has no extent; rank 0")
    }
    if(rank==1) {
        num_elem <- length(coord)
    }
    else if(rank==length(coord)) {
        coord <- matrix(coord, ncol=1)
        num_elem <- 1
    }
    else {
        if(byrow) {
            if(!is.matrix(coord)) {
                stop("coord has to be a matrix")
            }
            if(ncol(coord) != rank) {
                stop(paste("Number of columns of coord has to be equal to rank (for byrow=TRUE)", rank))
            }
            num_elem <- nrow(coord)
            coord <- t(coord)
        }
        else {
            if(!is.matrix(coord)) {
                stop("coord has to be a matrix")
            }
            if(nrow(coord) != rank) {
                stop(paste("Number of rows of coord has to be equal to rank (for byrow=FALSE)", rank))
            }
            num_elem <- nrow(coord)
        }
    }
    ## now capture the case when 0 elements are to be set
    if(num_elem == 0) {
        if(op==h5const$H5S_SELECT_SET) {
            ## need to change the selection to None
            herr <- .Call("R_H5Sselect_none", id, PACKAGE = "hdf5r")
            if(herr < 0) {
                stop("Error when setting selection to none")
            }
        }
        else {
            ## nothing to do; as either append of nothing or prepend of nothing (only set; append or prepend possible as operators)
            return(NULL)
        }
    }
    else {
        ## correct for first element 0
        coord <- coord - 1
        ## reverse all the coordinates
        coord_rev <- coord
        for(i in seq_len(rank)) {
            coord_rev[i,] <- coord[rank + 1 - i,]
        }
        coord <- coord_rev
        herr <- .Call("R_H5Sselect_elements", id, op, num_elem, coord, PACKAGE = "hdf5r")
        if(herr < 0) {
            stop("Error when selecting elements")
        }
    }
    return(NULL)
}

standalone_H5S_select_hyperslab <- function(id, start, count, stride=NULL, block=NULL, op=h5const$H5S_SELECT_SET) {

    rank <- standalone_H5S_get_simple_extent_ndims(id=id)
    if(is.null(stride)) {
        stride <- rep(1, rank)
    }
    if(is.null(block)) {
        block <- rep(1, rank)
    }
    if(length(start) != rank) {
        stop(paste("start has to be of the same length as the rank of the dataspace,", rank))
    }
    if(length(stride) != rank) {
        stop(paste("stride has to be of the same length as the rank of the dataspace,", rank))
    }
    if(length(count) != rank) {
        stop(paste("count has to be of the same length as the rank of the dataspace,", rank))
    }
    if(length(block) != rank) {
        stop(paste("block has to be of the same length as the rank of the dataspace,", rank))
    }
    ## correct for first element 0
    start <- start - 1
    herr <- .Call("R_H5Sselect_hyperslab", id, op, rev(start), rev(stride), rev(count), rev(block),
                  PACKAGE = "hdf5r")$return_val
    if(herr < 0) {
        stop("Error when selecting hyperslab")
    }
    return(NULL)
}



##' Select multiple hyperslabs in a space
##'
##' Selects multiple hyperslabs in a space. Before the selection, the space selection will be cleared.
##' @title Select multiple hyperslabs in a space
##' @param id The id of the space
##' @param hyperslab_array The array with the hyperslabs. Is of dimension num_dim x num_hyperslabs x 4. With the elements
##' being start, count, stride and block
##' @return \code{NULL}. The space has been manipulated as a side effect
##' @author Holger Hoefling
##' @keywords internal
standalone_H5S_select_multiple_hyperslab <- function(id, hyperslab_array) {
    num_hyperslabs <- dim(hyperslab_array)[[2]]

    stopifnot(num_hyperslabs > 0)
    
    ## select the first hyperslab
    start <- hyperslab_array[, 1, 1] - 1
    stride <- hyperslab_array[, 1, 3]
    count <- hyperslab_array[, 1, 2]
    block <- hyperslab_array[, 1, 4]
    herr <- .Call("R_H5Sselect_hyperslab", id, h5const$H5S_SELECT_SET, rev(start), rev(stride), rev(count), rev(block),
                  PACKAGE = "hdf5r")$return_val
    if(herr < 0) {
        stop("Error when selecting hyperslab")
    }
    
    
    if(num_hyperslabs > 1) {
        for(i in 2:num_hyperslabs) {
            start <- hyperslab_array[, i, 1] - 1
            stride <- hyperslab_array[, i, 3]
            count <- hyperslab_array[, i, 2]
            block <- hyperslab_array[, i, 4]
            herr <- .Call("R_H5Sselect_hyperslab", id, h5const$H5S_SELECT_OR, rev(start), rev(stride), rev(count), rev(block),
                          PACKAGE = "hdf5r")$return_val
            if(herr < 0) {
                stop("Error when selecting hyperslab")
            }
        }
    }
    return(NULL)
}



standalone_H5S_get_simple_extent_dims=function(id) {
    rank <- standalone_H5S_get_simple_extent_ndims(id)
    res <- suppressWarnings(.Call("R_H5Sget_simple_extent_dims", id, request_empty(rank), request_empty(rank), PACKAGE = "hdf5r"))
    if(res$return_val < 0) {
        stop("Error when retrieving extent of simple dataspace")
    }
    names(res) <- c("rank", "dims", "maxdims")
    res$dims <- rev(res$dims)
    res$maxdims <- rev(res$maxdims)
    return(res)                           
}