/// <summary>
/// Method to call before performing the actual saving.
/// </summary>
protected override void OnSave()
{
if (RootDirectoryRecord == null)
{
throw new InvalidOperationException("No DICOM files added, cannot save DICOM directory");
}
_directoryRecordSequence.Items.Clear();
var calculator = new DicomWriteLengthCalculator(FileMetaInfo.TransferSyntax, DicomWriteOptions.Default);
// ensure write length calculator does not include end of sequence item
//Dataset.Remove(DicomTag.DirectoryRecordSequence);
//_fileOffset = 128 + calculator.Calculate(FileMetaInfo) + calculator.Calculate(Dataset);
//Add the offset for the Directory Record sequence tag itself
//_fileOffset += 4;//sequence element tag
if (FileMetaInfo.TransferSyntax.IsExplicitVR)
{
_fileOffset = 128 + calculator.Calculate(FileMetaInfo) + calculator.Calculate(Dataset);
_fileOffset += 2; // vr
_fileOffset += 2; // padding
_fileOffset += 4; // length
}
else
{
_fileOffset = 128 + 4 + calculator.Calculate(FileMetaInfo) + calculator.Calculate(Dataset);
_fileOffset += 4; //sequence element tag
_fileOffset += 4; //length
}
AddDirectoryRecordsToSequenceItem(RootDirectoryRecord);
if (RootDirectoryRecord != null)
{
CalculateOffsets(calculator);
SetOffsets(RootDirectoryRecord);
Dataset.Add <uint>(
DicomTag.OffsetOfTheFirstDirectoryRecordOfTheRootDirectoryEntity,
RootDirectoryRecord.Offset);
var lastRoot = RootDirectoryRecord;
while (lastRoot.NextDirectoryRecord != null)
{
lastRoot = lastRoot.NextDirectoryRecord;
}
Dataset.Add <uint>(DicomTag.OffsetOfTheLastDirectoryRecordOfTheRootDirectoryEntity, lastRoot.Offset);
}
else
{
Dataset.Add <uint>(DicomTag.OffsetOfTheFirstDirectoryRecordOfTheRootDirectoryEntity, 0);
Dataset.Add <uint>(DicomTag.OffsetOfTheLastDirectoryRecordOfTheRootDirectoryEntity, 0);
}
}
private void CalculateOffsets(DicomWriteLengthCalculator calculator)
{
foreach (var item in Dataset.Get <DicomSequence>(DicomTag.DirectoryRecordSequence))
{
var record = item as DicomDirectoryRecord;
if (record == null)
{
throw new InvalidOperationException("Unexpected type for directory record: " + item.GetType());
}
record.Offset = _fileOffset;
_fileOffset += 4 + 4; //Sequence item tag;
_fileOffset += calculator.Calculate(record);
_fileOffset += 4 + 4; // Sequence Item Delimitation Item
}
_fileOffset += 4 + 4; // Sequence Delimitation Item
}