function h5ex_d_unlimgzip
%**************************************************************************
%
% This example shows how to create and extend an unlimited
% dataset with gzip compression.  The program first writes
% integers to a gzip compressed dataset with dataspace
% dimensions of DIM0xDIM1, then closes the file.  Next, it
% reopens the file, reads back the data, outputs it to the
% screen, extends the dataset, and writes new data to the
% extended portions of the dataset.  Finally it reopens the
% file again, reads back the data, and outputs it to the
% screen.
%
% This file is intended for use with HDF5 Library version 1.8
%**************************************************************************

FILE          = 'h5ex_d_unlimgzip.h5';
DIM0          = 4;
DIM1          = 7;
EDIM0         = 6;
EDIM1         = 10;
CHUNK0        = 4;
CHUNK1        = 4;

%
% Check if gzip compression is available and can be used for both
% compression and decompression.  Normally we do not perform error
% checking in these examples for the sake of clarity, but in this
% case we will make an exception because this filter is an
% optional part of the hdf5 library.
%
avail = H5Z.filter_avail('H5Z_FILTER_DEFLATE');
if (~avail)
    fprintf('gzip filter not available.\n');
    return;
end
filter_info = H5Z.get_filter_info('H5Z_FILTER_DEFLATE');
if (filter_info ~= 3)
    fprintf('gzip filter not available for encoding and decoding.\n');
    return;
end

%
% Initialize data.
%
wdata = zeros([DIM0,DIM1],'int32');
for i=1:DIM0
    for j=1:DIM1
        ii=i-1;
        jj=j-1;
        wdata(i,j) = ii * jj - jj;
    end
end

%
% Create a new file using the default properties.
%
file = H5F.create(FILE, 'H5F_ACC_TRUNC', 'H5P_DEFAULT', 'H5P_DEFAULT');

%
% Create dataspace with unlimited dimensions.
%
dims = [DIM0, DIM1];
maxdims = {'H5S_UNLIMITED', 'H5S_UNLIMITED'};
space = H5S.create_simple (2, fliplr(dims), fliplr(maxdims));

%
% Create the dataset creation property list, add the gzip
% compression filter and set the chunk size.
%
chunk = [CHUNK0, CHUNK1];
dcpl = H5P.create('H5P_DATASET_CREATE');
H5P.set_deflate(dcpl, 9);
H5P.set_chunk(dcpl, fliplr(chunk));

%
% Create the compressed unlimited dataset.
%
dset = H5D.create(file, 'DATASET', 'H5T_STD_I32LE', space, dcpl);

%
% Write the data to the dataset.
%
H5D.write(dset, 'H5T_NATIVE_INT', 'H5S_ALL', 'H5S_ALL', ...
    'H5P_DEFAULT', wdata);

%
% Close and release resources.
%
H5P.close(dcpl);
H5D.close(dset);
H5S.close(space);
H5F.close(file);

%
%% In this next section we read back the data, extend the dataset,
% and write new data to the extended portions.
%

%
% Open file and dataset using the default properties.
%
file = H5F.open(FILE, 'H5F_ACC_RDWR', 'H5P_DEFAULT');
dset = H5D.open(file, 'DATASET');

%
% Get dataspace and allocate memory for read buffer.
%
space = H5D.get_space(dset);
[~, dims] = H5S.get_simple_extent_dims(space);
dims = fliplr(dims);

%
% Read the data using the default properties.
%
rdata = H5D.read (dset, 'H5T_NATIVE_INT', 'H5S_ALL', 'H5S_ALL', ...
    'H5P_DEFAULT');

%
% Output the data to the screen.
%
fprintf ('Dataset before extension:\n');
for i=1:DIM0
    fprintf (' [');
    for j=1:DIM1
        fprintf (' %3d', rdata(i,j));
    end
    fprintf (']\n');
end

H5S.close(space);

%
% Extend the dataset.
%
extdims = [EDIM0, EDIM1];
H5D.extend(dset, fliplr(extdims));

%
% Retrieve the dataspace for the newly extended dataset.
%
space = H5D.get_space(dset);

%
% Initialize data for writing to the extended dataset.
%
wdata2 = zeros(extdims,'int32');
for i=1:EDIM0
    for j=1:EDIM1
        wdata2(i, j) = j-1;
    end
end

%
% Select the entire dataspace.
%
H5S.select_all(space);

%
% Subtract a hyperslab reflecting the original dimensions from the
% selection.  The selection now contains only the newly extended
% portions of the dataset.
%
start = [0, 0];
count = dims;
H5S.select_hyperslab(space, 'H5S_SELECT_NOTB', start, [], ...
    fliplr(count), []);

%
% Write the data to the selected portion of the dataset.
%
H5D.write(dset, 'H5T_NATIVE_INT', 'H5S_ALL', space, 'H5P_DEFAULT', ...
    wdata2);

%
% Close and release resources.
%
H5D.close(dset);
H5S.close(space);
H5F.close(file);

%
%% Now we simply read back the data and output it to the screen.
%

%
% Open file and dataset using the default properties.
%
file = H5F.open(FILE, 'H5F_ACC_RDONLY', 'H5P_DEFAULT');
dset = H5D.open(file, 'DATASET');

%
% Retrieve dataset creation property list.
%
dcpl = H5D.get_create_plist(dset);

%
% Retrieve and print the filter type.  Here we only retrieve the
% first filter because we know that we only added one filter.
%
[filter_type, ~, ~] = H5P.get_filter(dcpl, 0);
fprintf('\nFilter type is: ');
switch (filter_type)
    case H5ML.get_constant_value('H5Z_FILTER_DEFLATE')
        fprintf('H5Z_FILTER_DEFLATE\n');
        
    case H5ML.get_constant_value('H5Z_FILTER_SHUFFLE')
        fprintf('H5Z_FILTER_SHUFFLE\n');
        
    case H5ML.get_constant_value('H5Z_FILTER_FLETCHER32')
        fprintf('H5Z_FILTER_FLETCHER32\n');
        
    case H5ML.get_constant_value('H5Z_FILTER_SZIP')
        fprintf('H5Z_FILTER_SZIP\n');
        
end

%
% Get dataspace
%
space = H5D.get_space(dset);


%
% Read the data using the default properties.
%
rdata = H5D.read(dset, 'H5T_NATIVE_INT', 'H5S_ALL', 'H5S_ALL', ...
    'H5P_DEFAULT');

%
% Output the data to the screen.
%
fprintf('Dataset after extension:\n');
for i=1:EDIM0
    fprintf (' [');
    for j=1:EDIM1
        fprintf (' %3d', rdata(i,j));
    end
    fprintf (']\n');
end

%
% Close and release resources.
H5P.close(dcpl);
H5D.close(dset);
H5S.close(space);
H5F.close(file);