Merge branch 'exporters' into 'master'

Exporters

See merge request nsviz/visimpl!91

importers/CMakeLists.txt

@@ -2,21 +2,31 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)
 
 find_package(Qt5 COMPONENTS Core)
+find_package(HDF5 REQUIRED COMPONENTS C CXX)
+INCLUDE_DIRECTORIES (${HDF5_INCLUDE_DIR})
 
 set(SOURCES 
 	gdf2csv.cpp
 	txt2csv.cpp
+	hdf52csv.cpp
+	hdf52hdf5.cpp
 	)
 
 set(HEADERS
 	)
 
+# not used, only to annotate dependencies.
 set(EXTERNAL_LIBS
 	Qt5::Core
+	${HDF5_LIBRARIES}
 	)
 
 add_executable(gdf2csv gdf2csv.cpp)
 add_executable(txt2csv txt2csv.cpp)
-target_link_libraries(gdf2csv ${EXTERNAL_LIBS})
-target_link_libraries(txt2csv ${EXTERNAL_LIBS})
+add_executable(hdf52csv hdf52csv.cpp)
+add_executable(hdf52hdf5 hdf52hdf5.cpp)
+target_link_libraries(gdf2csv Qt5::Core)
+target_link_libraries(txt2csv Qt5::Core)
+target_link_libraries(hdf52csv ${HDF5_LIBRARIES})
+target_link_libraries(hdf52hdf5 ${HDF5_LIBRARIES})
 

importers/hdf52csv.cpp

+/*
+ * hdf52csv.cpp
+ *
+ *  Created on: Jan 31, 2023
+ *      Author: felix
+ */
+
+#include <H5Cpp.h>
+
+#include <cstring>
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <algorithm>
+#include <cassert>
+#include <memory>
+#include <sys/stat.h>
+#include <limits.h>
+
+struct dotSeparator: std::numpunct<char>
+{
+    char do_decimal_point() const { return '.'; }
+};
+
+template<class T> void ignore( const T& ) { }
+
+void printUsage(const char *filename)
+{
+  const std::string name = (filename ? std::string(filename) : "HDF52CSV");
+
+  std::cout << name << " - Generates CSV network and connections file from HDF5 data." << '\n';
+  std::cout << "Usage: " << name << " <hdf5_source_file>" << std::endl;
+  std::exit(-1);
+}
+
+const char NETWORK_FILENAME[] = "H5_network.csv";
+const char CONNECTIONS_FILENAME[] = "H5_connections.csv";
+
+const char CELLS_TAG[]="cells/positions";
+const char MAPS_TAG[]="cells/type_maps";
+const char CONNECTIONS_TAG[]="cells/connections";
+const char MORPHOLOGIES_TAG[] ="morphologies";
+
+const char SEPARATOR = ',';
+const char NEWLINE = '\n';
+
+bool countConnections = true;
+
+std::vector<std::string> CELL_TYPES = { "granule_cell", "glomerulus", "golgi_cell", "purkinje_cell",
+                                        "stellate_cell", "basket_cell", "mossy_fibers" };
+
+// Substitute with an include to filtered ids.
+std::vector<uint32_t> toFilter;
+
+int main(int argc, char* argv[])
+{
+  if(argc < 2) printUsage(argv[0]);
+
+  struct stat buf;
+  if(stat(argv[1], &buf) != 0)
+  {
+    std::cerr << "Unable to find file: " << argv[1] << std::endl;
+    exit(-1);
+  }
+
+  if(!S_ISREG(buf.st_mode))
+  {
+    std::cerr << "Parameter " << argv[1] << " is not a file." << std::endl;
+    exit(-1);
+  }
+
+  // Check whether file referenced by the path is an Hdf5 format file or not.
+  if( !H5::H5File::isHdf5( argv[1] ))
+  {
+    std::cerr << "File " << argv[1] << " is not a HDF5 file!" << std::endl;
+    std::exit(-1);
+  }
+
+  // open file
+  auto sourceFile = H5::H5File( argv[1], H5F_ACC_RDONLY );
+
+  for(const auto &tag: { CELLS_TAG, CONNECTIONS_TAG })
+  {
+    if(!H5Lexists(sourceFile.getLocId(), tag, H5P_DEFAULT) > 0)
+    {
+      std::cerr << "File " << argv[1] << " has not the correct format, "
+                << tag << " tag is missing!" << std::endl;
+      std::exit(-1);
+    }
+  }
+
+  std::ofstream nFile, cFile;
+  nFile.open(NETWORK_FILENAME, std::fstream::out|std::fstream::trunc);
+
+  if(nFile.fail())
+  {
+    std::cerr << "Unable to open output filename: " << NETWORK_FILENAME << std::endl;
+    std::exit(-1);
+  }
+
+  // write floating point numbers with dot separation no matter the locale
+  nFile.imbue(std::locale(nFile.getloc(), new dotSeparator()));
+  nFile << "gid" << SEPARATOR << "type" << SEPARATOR << "x" << SEPARATOR << "y" << SEPARATOR << "z" << NEWLINE;
+  auto dataSet = sourceFile.openDataSet(CELLS_TAG);
+
+  hsize_t dims[2];
+  dataSet.getSpace().getSimpleExtentDims( dims );
+  assert(dataSet.getSpace().getSimpleExtentNdims() == 2);
+  assert(dataSet.getTypeClass() == H5T_FLOAT);
+
+  auto buffer = new float[dims[0]*dims[1]];
+
+  // load positions
+  dataSet.read( reinterpret_cast<void*>(buffer), H5::PredType::IEEE_F32LE);
+
+  unsigned long idCount = 0;
+  for(size_t idx = 0; idx < dims[0]*dims[1]; )
+  {
+    const auto id = static_cast<uint32_t>(buffer[idx]);
+    const auto type = static_cast<uint32_t>(buffer[idx+1]);
+    bool hasId = toFilter.empty();
+    if(!hasId)
+    {
+      hasId = std::find(toFilter.cbegin(), toFilter.cend(), id) != toFilter.cend();
+    }
+
+    if(hasId)
+    {
+      ++idCount;
+      nFile << id << SEPARATOR << CELL_TYPES[type] << SEPARATOR;
+      idx += dims[1]-3;
+      nFile << buffer[idx+0] << SEPARATOR << buffer[idx+1] << SEPARATOR << buffer[idx+2] << NEWLINE;
+    }
+    else idx += dims[1]-3;
+    idx+=3;
+  }
+
+  delete [] buffer;
+  buffer = nullptr;
+  dataSet.close();
+
+  std::cout << "Write network file: " << NETWORK_FILENAME << " - " << idCount << " ids" << std::endl;
+
+  nFile.flush();
+  nFile.close();
+
+  cFile.open(CONNECTIONS_FILENAME, std::fstream::out|std::fstream::trunc);
+
+  if(cFile.fail())
+  {
+    std::cerr << "Unable to open output filename: " << CONNECTIONS_FILENAME << std::endl;
+    std::exit(-1);
+  }
+
+  // write floating point numbers with dot separation no matter the locale
+  cFile.imbue(std::locale(cFile.getloc(), new dotSeparator()));
+
+  if(countConnections)
+    cFile << "source" << SEPARATOR << "target" << SEPARATOR << "count" << SEPARATOR << "type" << NEWLINE;
+  else
+    cFile << "source" << SEPARATOR << "target" << SEPARATOR << "type" << NEWLINE;
+
+  auto group = sourceFile.openGroup(CONNECTIONS_TAG);
+  const unsigned int objNum = group.getNumObjs( );
+
+  idCount = 0;
+  for( unsigned int i = 0; i < objNum; i++ )
+  {
+    // Get object type.
+    H5G_obj_t type = group.getObjTypeByIdx( i );
+
+    // Get object name.
+    const std::string name = group.getObjnameByIdx( i );
+
+    // Check if type is a dataset.
+    if( type != H5G_obj_t::H5G_DATASET )
+      continue;
+
+    // Open dataset.
+    H5::DataSet innerDs = group.openDataSet( name );
+    memset(dims, 0, 2*sizeof(hsize_t));
+    innerDs.getSpace().getSimpleExtentDims( dims );
+    assert(innerDs.getSpace().getSimpleExtentNdims() == 2);
+    assert(innerDs.getTypeClass() == H5T_FLOAT);
+
+    if(dims[0] == 0 || dims[1] == 0)
+      continue;
+
+    buffer = new float[dims[0]*dims[1]];
+
+    innerDs.read( reinterpret_cast<void*>(buffer), H5::PredType::IEEE_F32LE );
+
+    if(countConnections)
+    {
+      uint32_t aid1 = std::numeric_limits<uint32_t>::max();
+      uint32_t aid2 = std::numeric_limits<uint32_t>::max();
+      unsigned long cCount = 0;
+
+      for(size_t idx = 0; idx < dims[0]*dims[1]; )
+      {
+        auto id1 = static_cast<uint32_t>(buffer[idx]);
+        auto id2 = static_cast<uint32_t>(buffer[idx+1]);
+
+        if(id1 == aid1 && id2 == aid2)
+        {
+          ++cCount;
+          ++idCount;
+          idx += dims[1];
+          continue;
+        }
+        else
+        {
+          if(aid1 != std::numeric_limits<uint32_t>::max() && (aid1 != id1 || aid2 != id2))
+          {
+            cFile << aid1 << SEPARATOR << aid2 << SEPARATOR << cCount << SEPARATOR << name << NEWLINE;
+            aid1 = std::numeric_limits<uint32_t>::max();
+            aid2 = std::numeric_limits<uint32_t>::max();
+            cCount = 0;
+          }
+        }
+
+        bool hasIds = toFilter.empty();
+        if(!hasIds)
+        {
+          const auto hasId1 = std::find(toFilter.cbegin(), toFilter.cend(), id1) != toFilter.cend();
+          const auto hasId2 = std::find(toFilter.cbegin(), toFilter.cend(), id2) != toFilter.cend();
+          hasIds = (hasId1 && hasId2);
+        }
+
+        if(hasIds)
+        {
+          ++idCount;
+          ++cCount;
+          aid1 = id1;
+          aid2 = id2;
+        }
+
+        idx += dims[1];
+      }
+
+      if(aid1 != std::numeric_limits<uint32_t>::max())
+        cFile << aid1 << SEPARATOR << aid2 << SEPARATOR << cCount << SEPARATOR << name << NEWLINE;
+    }
+    else
+    {
+      for(size_t idx = 0; idx < dims[0]*dims[1]; )
+      {
+        auto id1 = static_cast<uint32_t>(buffer[idx]);
+        auto id2 = static_cast<uint32_t>(buffer[idx+1]);
+
+        bool hasIds = toFilter.empty();
+        if(!hasIds)
+        {
+          const auto hasId1 = std::find(toFilter.cbegin(), toFilter.cend(), id1) != toFilter.cend();
+          const auto hasId2 = std::find(toFilter.cbegin(), toFilter.cend(), id2) != toFilter.cend();
+          hasIds = (hasId1 && hasId2);
+        }
+
+        if(hasIds)
+        {
+          ++idCount;
+          cFile << id1 << SEPARATOR << id2 << SEPARATOR << name << NEWLINE;
+        }
+
+        idx += dims[1];
+      }
+    }
+    delete [] buffer;
+    innerDs.close();
+  }
+
+  std::cout << "Write connections file: " << CONNECTIONS_FILENAME << " - " << idCount << " connections" << std::endl;
+
+  cFile.flush();
+  cFile.close();
+
+  sourceFile.close();
+
+  return 0;
+}

importers/hdf52hdf5.cpp

+/*
+ * hdf52hdf5.cpp
+ *
+ *  Created on: Jan 31, 2023
+ *      Author: felix
+ */
+
+#include <H5Cpp.h>
+
+#include <cstring>
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <algorithm>
+#include <cassert>
+#include <memory>
+#include <sys/stat.h>
+
+// should get this from file, not store it here. Use an include
+const std::vector<std::string> CELL_TYPES = { "granule_cell", "glomerulus", "golgi_cell", "purkinje_cell",
+                                              "stellate_cell", "basket_cell", "mossy_fibers" };
+void printUsage(const char *filename)
+{
+  const std::string name = (filename ? std::string(filename) : "TXTTOCSV");
+
+  std::cout << name << " - Generates HDF5 with filtered ids." << '\n';
+  std::cout << "Usage: " << name << " <hdf5_source_file> <hdf5_target_file>" << std::endl;
+  std::exit(-1);
+}
+
+// #include "toFilter.h"
+// modify to filter ids, maybe use another input for this? If empty all ids goes in target.
+std::vector<uint32_t> toFilter;
+
+const char CELLS_TAG[]="cells/positions";
+const char MAPS_TAG[]="cells/type_maps";
+const char CONNECTIONS_TAG[]="cells/connections";
+const char MORPHOLOGIES_TAG[] ="morphologies";
+
+// to store cell ids, type and coordinates. Has to be double to write to HDF5 dataset.
+struct Coords
+{
+    double id;
+    double type;
+    double x;
+    double y;
+    double z;
+
+    Coords():id{0}, type{0}, x{0}, y{0}, z{0} {};
+    Coords(double i, double t, double _x, double _y, double _z): id{i}, type{t}, x{_x}, y{_y}, z{_z} {};
+};
+
+auto checkError = [](const int value) { if(value < 0) { std::cerr << "ERROR: " << __FILE__ << ":" << __LINE__ << std::endl; exit(1); } };
+
+void H5WritePositions(hid_t to, const std::vector<Coords> &coords)
+{
+  if(coords.empty()) return;
+
+  hsize_t dims[2]{coords.size(), 5};
+
+  // Create a dataset
+  auto group_id = H5Gopen2(to, "/cells", H5P_DEFAULT);
+  auto dspace_id = H5Screate_simple(2, dims, NULL);
+  auto dset_id = H5Dcreate2(group_id, "positions", H5T_NATIVE_DOUBLE, dspace_id, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+
+  // Write the data
+  auto status = H5Dwrite(dset_id, H5T_NATIVE_DOUBLE, H5S_ALL, H5S_ALL, H5P_DEFAULT, coords.data());
+  checkError(status);
+
+  // Close dataset after writing
+  status = H5Dclose(dset_id);
+  checkError(status);
+
+  status = H5Gclose(group_id);
+  checkError(status);
+}
+
+void H5CopyAttribute(hid_t from, hid_t to, const char* propertyName)
+{
+  hid_t attr = H5Aopen(from, propertyName, H5P_DEFAULT);
+  auto aSpace = H5Aget_space(attr);
+
+  H5A_info_t aInfo;
+  auto status = H5Aget_info(attr, &aInfo);
+  checkError(status);
+  auto aType = H5Aget_type(attr);
+
+  unsigned char *buffer = new unsigned char[aInfo.data_size];
+  memset(buffer, 0, aInfo.data_size);
+  status = H5Aread(attr, aType, buffer);
+  checkError(status);
+
+  auto newAttr = H5Acreate2(to, propertyName, aType, aSpace,H5P_DEFAULT, H5P_DEFAULT);
+  checkError(newAttr);
+  status = H5Awrite(newAttr, aType, buffer);
+  checkError(status);
+
+  H5free_memory(buffer);
+  H5Sclose(aSpace);
+  H5Tclose(aType);
+  H5Aclose(attr);
+  H5Aclose(newAttr);
+}
+
+void H5copy(hid_t from, const char *from_tag, hid_t to, const char *to_tag)
+{
+  auto status = H5Ocopy(from, from_tag, to, to_tag, H5P_DEFAULT, H5P_DEFAULT);
+  checkError(status);
+}
+
+void H5writeMap(hid_t to, std::string name, std::vector<uint32_t> &gids)
+{
+  hsize_t dims[1]{gids.size()};
+
+  auto group_id = H5Gopen2(to, "/cells/type_maps", H5P_DEFAULT);
+
+  // Create a dataset
+  auto dspace_id = H5Screate_simple(1, dims, NULL);
+  auto dset_id = H5Dcreate2( group_id, name.c_str(), H5T_NATIVE_INT, dspace_id, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+
+  // Write the data
+  auto status = H5Dwrite(dset_id, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, gids.data());
+  checkError(status);
+
+  // Close dataset after writing
+  status = H5Dclose(dset_id);
+  checkError(status);
+
+  status = H5Gclose(group_id);
+  checkError(status);
+}
+
+void H5writeConnections(hid_t to, std::string name, std::vector<std::pair<uint32_t, uint32_t>> connections)
+{
+  std::vector<std::pair<double, double>> others;
+  for(size_t i = 0; i < connections.size(); ++i)
+  {
+    auto value = connections.at(i);
+
+    if(!toFilter.empty())
+    {
+      auto it1 = std::find(toFilter.cbegin(), toFilter.cend(), value.first);
+      auto it2 = std::find(toFilter.cbegin(), toFilter.cend(), value.second);
+      if(toFilter.cend() == it1 || toFilter.cend() == it2)
+      {
+        continue;
+      }
+    }
+
+    others.emplace_back(value.first, value.second);
+  }
+
+  if(others.empty()) return;
+
+  hsize_t dims[2]{others.size(), 2};
+
+  auto group_id = H5Gopen2(to, "/cells/connections", H5P_DEFAULT);
+  // Create a dataset
+  auto dspace_id = H5Screate_simple(2, dims, NULL);
+  auto dset_id = H5Dcreate2( group_id, name.c_str(), H5T_NATIVE_DOUBLE, dspace_id, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+
+  // Write the data
+  auto status = H5Dwrite(dset_id, H5T_NATIVE_DOUBLE, H5S_ALL, H5S_ALL, H5P_DEFAULT, others.data());
+  checkError(status);
+
+  // Close dataset after writing
+  status = H5Dclose(dset_id);
+  checkError(status);
+
+  status = H5Gclose(group_id);
+  checkError(status);
+}
+
+int main(int argc, char* argv[])
+{
+  if(argc < 3) printUsage(argv[0]);
+
+  struct stat buf;
+  if(stat(argv[1], &buf) != 0)
+  {
+    std::cerr << "Unable to find file: " << argv[1] << std::endl;
+    exit(-1);
+  }
+
+  if(!S_ISREG(buf.st_mode))
+  {
+    std::cerr << "Parameter " << argv[1] << " is not a file." << std::endl;
+    exit(-1);
+  }
+
+  if(stat(argv[2], &buf) == 0)
+  {
+    std::cerr << "Destination file: " << argv[2] << " already exists." << std::endl;
+    exit(-1);
+  }
+
+  // Check whether file referenced by the path is an Hdf5 format file or not.
+  if( !H5::H5File::isHdf5( argv[1] ))
+  {
+    std::cerr << "File " << argv[1] << " is not a HDF5 file!" << std::endl;
+    return 0;
+  }
+
+  // open files
+  auto sourceFile = H5::H5File( argv[1], H5F_ACC_RDONLY );
+  auto targetFile = H5Fcreate( argv[2], H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+
+  for(const auto &tag: { CELLS_TAG, CONNECTIONS_TAG, MORPHOLOGIES_TAG, MAPS_TAG })
+  {
+    if(!H5Lexists(sourceFile.getLocId(), tag, H5P_DEFAULT) > 0)
+    {
+      std::cerr << "File " << argv[1] << " has not the correct format, "
+                << tag << " tag is missing or misplaced!" << std::endl;
+      return -1;
+    }
+  }
+
+  // copy morphologies
+  H5copy(sourceFile.getLocId(), MORPHOLOGIES_TAG, targetFile, MORPHOLOGIES_TAG);
+
+  // open cells and copy/filter
+  H5Gcreate2(targetFile, "/cells", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  auto targetCellId = H5Gopen2(targetFile, "/cells", H5P_DEFAULT);
+  auto sourceCellId = H5Gopen2(sourceFile.getLocId(), "cells", H5P_DEFAULT);
+  H5CopyAttribute(sourceCellId, targetCellId, "types");
+  H5Gcreate2(targetCellId, "type_maps", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  H5Gcreate2(targetCellId, "connections", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  H5Gclose(targetCellId);
+
+  auto dataSet = sourceFile.openDataSet(CELLS_TAG);
+
+  hsize_t dims[2];
+  dataSet.getSpace().getSimpleExtentDims( dims );
+  assert(dataSet.getSpace().getSimpleExtentNdims() == 2);
+  assert(dataSet.getTypeClass() == H5T_FLOAT);
+
+  auto buffer = new float[dims[0]*dims[1]];
+
+  // load positions
+  dataSet.read( reinterpret_cast<void*>(buffer), H5::PredType::IEEE_F32LE );
+
+  std::vector<Coords> subset;
+  std::vector<uint32_t> types;
+  for(size_t idx = 0; idx < dims[0]*dims[1]; )
+  {
+    const auto id = static_cast<uint32_t>(buffer[idx]);
+    bool hasId = toFilter.empty();
+    if(!hasId)
+    {
+      auto it = std::find(toFilter.cbegin(), toFilter.cend(), id);
+      hasId = it != toFilter.cend();
+    }
+
+    if(hasId)
+    {
+      const auto type = static_cast<uint32_t>(buffer[idx+1]);
+      idx += dims[1]-3;
+      subset.emplace_back(id, type, buffer[idx+0],buffer[idx+1],buffer[idx+2]);
+      idx+=3;
+    }
+  }
+
+  delete [] buffer;
+  buffer = nullptr;
+
+  dataSet.close();
+
+  auto sortCoords = [](Coords &lhs, Coords &rhs){ return lhs.id < rhs.id; };
+  std::sort(subset.begin(), subset.end(), sortCoords);
+
+  H5WritePositions(targetFile, subset);
+
+  // group maps.
+  if(H5Lexists(sourceFile.getLocId(), MAPS_TAG, H5P_DEFAULT) > 0)
+  {
+    auto group = sourceFile.openGroup(MAPS_TAG);
+    const unsigned int objNum = group.getNumObjs( );
+
+    for( unsigned int i = 0; i < objNum; i++ )
+    {
+      // Get object type.
+      H5G_obj_t type = group.getObjTypeByIdx( i );
+
+      // Get object name.
+      const std::string name = group.getObjnameByIdx( i );
+
+      // Check if type is a dataset.
+      if( type != H5G_obj_t::H5G_DATASET )
+        continue;
+
+      // Open dataset.
+      H5::DataSet innerDs = group.openDataSet( name );
+      memset(dims, 0, 2*sizeof(hsize_t));
+      innerDs.getSpace().getSimpleExtentDims( dims );
+      assert(innerDs.getSpace().getSimpleExtentNdims() == 1);
+
+      assert(innerDs.getTypeClass() == H5T_INTEGER);
+      auto integerType = innerDs.getIntType();
+
+      if(dims[0] == 0)
+        continue;
+
+      buffer = new float[dims[0]];
+
+      innerDs.read( reinterpret_cast<void*>(buffer), H5::PredType::IEEE_F32LE );
+
+      std::vector<uint32_t> gids;
+      for(size_t idx = 0; idx < dims[0]; )
+      {
+        const auto id = static_cast<uint32_t>(buffer[idx]);
+        bool hasId = toFilter.empty();
+        if(!hasId)
+          hasId = std::find(toFilter.cbegin(), toFilter.cend(), id) != toFilter.cend();
+
+        if(hasId)
+          gids.emplace_back(id);
+
+        ++idx;
+      }
+
+      delete [] buffer;
+      buffer = nullptr;
+      const auto groupName = "group " + name;
+      innerDs.close();
+
+      H5writeMap(targetFile, name, gids);
+    }
+
+    group.close();
+  }
+
+  // groups by connections
+  if(H5Lexists(sourceFile.getLocId(), CONNECTIONS_TAG, H5P_DEFAULT) > 0)
+  {
+    auto group = sourceFile.openGroup(CONNECTIONS_TAG);
+    const unsigned int objNum = group.getNumObjs( );
+
+    for( unsigned int i = 0; i < objNum; i++ )
+    {
+      // Get object type.
+      H5G_obj_t type = group.getObjTypeByIdx( i );
+
+      // Get object name.
+      const std::string name = group.getObjnameByIdx( i );
+
+      // Check if type is a dataset.
+      if( type != H5G_obj_t::H5G_DATASET )
+        continue;
+
+      // Open dataset.
+      H5::DataSet innerDs = group.openDataSet( name );
+      memset(dims, 0, 2*sizeof(hsize_t));
+      innerDs.getSpace().getSimpleExtentDims( dims );
+      assert(innerDs.getSpace().getSimpleExtentNdims() == 2);
+
+      assert(innerDs.getTypeClass() == H5T_FLOAT);
+
+      if(dims[0] == 0 || dims[1] == 0)
+        continue;
+
+      buffer = new float[dims[0]*dims[1]];
+
+      innerDs.read( reinterpret_cast<void*>(buffer), H5::PredType::IEEE_F32LE );
+
+      std::vector<std::pair<uint32_t, uint32_t>> connections;
+
+      std::vector<uint32_t> gids;
+      for(size_t idx = 0; idx < dims[0]*dims[1]; )
+      {
+        auto sou = static_cast<uint32_t>(buffer[idx]);
+        auto tar = static_cast<uint32_t>(buffer[idx+1]);
+        bool hasIds = toFilter.empty();
+        if(!hasIds)
+        {
+          auto it1 = std::find(toFilter.cbegin(), toFilter.cend(), sou);
+          auto it2 = std::find(toFilter.cbegin(), toFilter.cend(), tar);
+
+          hasIds = (it1 != toFilter.cend() && it2 != toFilter.cend());
+        }
+
+        if(hasIds)
+          connections.emplace_back(sou, tar);
+
+        idx += dims[1];
+      }
+      delete [] buffer;
+      buffer = nullptr;
+      const auto groupName = "connection " + name;
+      innerDs.close();
+
+      H5writeConnections(targetFile, name, connections);
+    }
+
+    group.close();
+  }
+
+  sourceFile.close();
+
+  H5Fflush(targetFile, H5F_SCOPE_GLOBAL);
+  H5Fclose(targetFile);
+
+  return 0;
+}
+