Add h5ex_d_checksum example

Update #318

examples/hdfgroup/H5D/CMakeLists.txt

@@ -1,3 +1,6 @@
 
 add_executable(h5ex_d_alloc h5ex_d_alloc.cpp)
-target_link_libraries(h5ex_d_alloc h5cpp) 
+target_link_libraries(h5ex_d_alloc h5cpp) 
+
+add_executable(h5ex_d_checksum h5ex_d_checksum.cpp)
+target_link_libraries(h5ex_d_checksum h5cpp)

examples/hdfgroup/H5D/h5ex_d_checksum.cpp

@@ -0,0 +1,173 @@
+/************************************************************
+
+  This example shows how to read and write data to a dataset
+  using the Fletcher32 checksum filter.  The program first
+  checks if the Fletcher32 filter is available, then if it
+  is it writes integers to a dataset using Fletcher32, then
+  closes the file.  Next, it reopens the file, reads back
+  the data, checks if the filter detected an error and
+  outputs the type of filter and the maximum value in the
+  dataset to the screen.
+
+  This file is intended for use with HDF5 Library version 1.8
+
+ ************************************************************/
+
+#include <h5cpp/hdf5.hpp>
+#include <array>
+#include <algorithm>
+
+#define FILE            "h5ex_d_checksum.h5"
+#define DATASET         "DS1"
+#define DIM0            32
+#define DIM1            64
+#define CHUNK0          4
+#define CHUNK1          8
+
+using buffer_type = std::array<int32_t,DIM0*DIM1>;
+
+int32_t generator()
+{
+  static size_t i = 0;
+  static size_t j = 0;
+
+  i = i<DIM0 ? i++ : 0;
+  j = j<DIM1 ? j++ : 0;
+
+  return i*j-j;
+}
+
+using namespace hdf5;
+
+void write_data()
+{
+    buffer_type  buffer;
+    std::generate(buffer.begin(),buffer.end(),generator);
+    /*
+     * Create a new file using the default properties.
+     */
+    file::File file = file::create(FILE,file::AccessFlags::TRUNCATE);
+
+    /*
+     * Create dataspace.  Setting maximum size to NULL sets the maximum
+     * size to be the current size.
+     */
+    dataspace::Simple space({DIM0,DIM1});
+
+    /*
+     * Create the dataset creation property list, add the Fletcher32 filter
+     * and set the chunk size.
+     */
+    property::LinkCreationList lcpl;
+    property::DatasetCreationList dcpl;
+    filter::Fletcher32 fletcher32;
+    fletcher32(dcpl);
+    dcpl.layout(property::DatasetLayout::CHUNKED);
+    dcpl.chunk(Dimensions{CHUNK0,CHUNK1});
+
+
+    /*
+     * Create the dataset and write data to disk
+     */
+    node::Dataset dset(file.root(),DATASET,datatype::create<int32_t>(),space,lcpl,dcpl);
+    dset.write(buffer);
+}
+
+void read_data()
+{
+
+   /*
+    * Open file and dataset using the default properties.
+    */
+   file::File file = file::open(FILE,file::AccessFlags::READONLY);
+   node::Dataset dset = file.root()[DATASET];
+
+   /*
+    * Retrieve dataset creation property list.
+    */
+   property::DatasetCreationList dcpl = dset.creation_list();
+
+   /*
+    * Retrieve and print the filter type.  Here we only retrieve the
+    * first filter because we know that we only added one filter.
+    */
+   size_t nelmts = 0;
+   unsigned int flags = 0, filter_info = 0;
+   H5Z_filter_t filter_type = H5Pget_filter (static_cast<hid_t>(dcpl), 0,
+                                             &flags, &nelmts, NULL, 0, NULL,
+                                             &filter_info);
+   printf ("Filter type is: ");
+   switch (filter_type) {
+       case H5Z_FILTER_DEFLATE:
+           printf ("H5Z_FILTER_DEFLATE\n");
+           break;
+       case H5Z_FILTER_SHUFFLE:
+           printf ("H5Z_FILTER_SHUFFLE\n");
+           break;
+       case H5Z_FILTER_FLETCHER32:
+           printf ("H5Z_FILTER_FLETCHER32\n");
+           break;
+       case H5Z_FILTER_SZIP:
+           printf ("H5Z_FILTER_SZIP\n");
+           break;
+       case H5Z_FILTER_NBIT:
+           printf ("H5Z_FILTER_NBIT\n");
+           break;
+       case H5Z_FILTER_SCALEOFFSET:
+           printf ("H5Z_FILTER_SCALEOFFSET\n");
+   }
+
+   /*
+    * Read the data using the default properties.
+    */
+   buffer_type buffer;
+   dset.read(buffer);
+
+   /*
+    * Check if the read was successful.  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 is how the
+    * fletcher32 checksum filter reports data errors.
+    */
+    //We somehow need to introduce some error checking here - at best we
+    //could somehow manipulate the data to force some error reporting.
+
+}
+
+int
+main (void)
+{
+    /*
+     * Check if the Fletcher32 filter is available and can be used for
+     * both encoding and decoding.  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.
+     */
+    htri_t avail = H5Zfilter_avail(H5Z_FILTER_FLETCHER32);
+    unsigned int filter_info;
+    if (!avail) {
+        printf ("Fletcher32 filter not available.\n");
+        return 1;
+    }
+    herr_t status = H5Zget_filter_info (H5Z_FILTER_FLETCHER32, &filter_info);
+    if ( !(filter_info & H5Z_FILTER_CONFIG_ENCODE_ENABLED) ||
+                !(filter_info & H5Z_FILTER_CONFIG_DECODE_ENABLED) ) {
+        printf ("Fletcher32 filter not available for encoding and decoding.\n");
+        return 1;
+    }
+
+    /*
+     * Initialize data.
+     */
+
+    write_data();
+    /*
+     * Now we begin the read section of this example.
+     */
+    read_data();
+
+
+
+    return 0;
+}