Cookbook

This page contains code snippets that show how a particular task may be accomplished in HDF.PInvoke. All examples using hid_t assume the statement using hid_t = System.Int32; at the top of the source file.

Attributes

String Attributes

This snippet reads the value from an attribute attached to the specified objectId.

private bool ReadStringAttribute(hid_t objectId, string title, out string value)
{
  value = "";

  hid_t attributeId = 0;
  hid_t typeId = 0;

  try
  {
    attributeId = H5A.open(objectId, title);
    typeId = H5A.get_type(attributeId);
    var sizeData = H5T.get_size(typeId);
    var size = sizeData.ToInt32();
    byte[] strBuffer = new byte[size];

    var aTypeMem = H5T.get_native_type(typeId, H5T.direction_t.ASCEND);
    GCHandle pinnedArray = GCHandle.Alloc(strBuffer, GCHandleType.Pinned);
    H5A.read(attributeId, aTypeMem, pinnedArray.AddrOfPinnedObject());
    pinnedArray.Free();
    H5T.close(aTypeMem);

    value = System.Text.ASCIIEncoding.ASCII.GetString(strBuffer);

    return true;
  }
  catch (Exception ex)
  {
    return false;
  }
  finally
  {
    if (attributeId != null) H5A.close(attributeId);
    if (typeId != null) H5T.close(typeId);
  }
}

Here we create an attribute attached to the given objectId:

private bool CreateStringAttribute(hid_t objectId, string title, string description)
{
  hid_t attributeSpace = 0;
  hid_t stringId = 0;
  hid_t attributeId = 0;

  try
  {
    attributeSpace = H5S.create(H5S.class_t.SCALAR);
    stringId = H5T.copy(H5T.C_S1);
    H5T.set_size(stringId, new IntPtr(description.Length));
    attributeId = H5A.create(objectId, title, stringId, attributeSpace);

    IntPtr descriptionArray = Marshal.StringToHGlobalAnsi(description);
    H5A.write(attributeId, stringId, descriptionArray);

    Marshal.FreeHGlobal(descriptionArray);

    return true;
  }
  catch (Exception ex)
  {
    return false;
  }
  finally
  {
    if (attributeId != 0) H5A.close(attributeId);
    if (stringId != 0) H5T.close(stringId);
    if (attributeSpace != 0) H5S.close(attributeSpace);
  }
}