private void ParsePreamble(IByteSource source, object state)
{
try {
if (!source.Require(132, ParsePreamble, state))
{
return;
}
_source.Skip(128);
if (_source.GetUInt8() != 'D' ||
_source.GetUInt8() != 'I' ||
_source.GetUInt8() != 'C' ||
_source.GetUInt8() != 'M')
{
throw new DicomReaderException("Invalid preamble found in DICOM file parser");
}
DicomReaderCallbackObserver obs = new DicomReaderCallbackObserver();
obs.Add(DicomTag.TransferSyntaxUID, delegate(object sender, DicomReaderEventArgs ea) {
try {
string uid = Encoding.ASCII.GetString(ea.Data.Data);
_syntax = DicomTransferSyntax.Parse(uid);
} catch {
}
});
_source.Endian = _syntax.Endian;
_reader.IsExplicitVR = _syntax.IsExplicitVR;
_reader.BeginRead(_source, new DicomReaderMultiObserver(obs, _fmiObserver), FileMetaInfoStopTag, OnFileMetaInfoParseComplete, null);
} catch (Exception e) {
if (_exception == null)
{
_exception = e;
}
_result = DicomReaderResult.Error;
} finally {
if (_result != DicomReaderResult.Processing && _result != DicomReaderResult.Suspended)
{
_async.Set();
}
}
}
private void ParsePreamble(IByteSource source, object state)
{
try {
if (!source.Require(132, ParsePreamble, state))
{
return;
}
// mark file origin
_source.Mark();
// test for DICM preamble
_source.Skip(128);
if (_source.GetUInt8() == 'D' &&
_source.GetUInt8() == 'I' &&
_source.GetUInt8() == 'C' &&
_source.GetUInt8() == 'M')
{
_fileFormat = DicomFileFormat.DICOM3;
}
// test for incorrect syntax in file meta info
do
{
if (_fileFormat == DicomFileFormat.DICOM3)
{
// move milestone to after preamble
_source.Mark();
}
else
{
// rewind to origin milestone
_source.Rewind();
}
// test for file meta info
var group = _source.GetUInt16();
if (group > 0x00ff)
{
_source.Endian = Endian.Big;
_syntax = DicomTransferSyntax.ExplicitVRBigEndian;
group = Endian.Swap(group);
}
if (group > 0x00ff)
{
// invalid starting tag
_fileFormat = DicomFileFormat.Unknown;
_source.Rewind();
break;
}
if (_fileFormat == DicomFileFormat.Unknown)
{
if (group == 0x0002)
{
_fileFormat = DicomFileFormat.DICOM3NoPreamble;
}
else
{
_fileFormat = DicomFileFormat.DICOM3NoFileMetaInfo;
}
}
var element = _source.GetUInt16();
var tag = new DicomTag(group, element);
// test for explicit VR
var vrt = Encoding.ASCII.GetBytes(tag.DictionaryEntry.ValueRepresentations[0].Code);
var vrs = _source.GetBytes(2);
if (vrt[0] != vrs[0] || vrt[1] != vrs[1])
{
// implicit VR
if (_syntax.Endian == Endian.Little)
{
_syntax = DicomTransferSyntax.ImplicitVRLittleEndian;
}
else
{
_syntax = DicomTransferSyntax.ImplicitVRBigEndian;
}
}
_source.Rewind();
} while (_fileFormat == DicomFileFormat.Unknown);
if (_fileFormat == DicomFileFormat.Unknown)
{
throw new DicomReaderException("Attempted to read invalid DICOM file");
}
var obs = new DicomReaderCallbackObserver();
if (_fileFormat != DicomFileFormat.DICOM3)
{
obs.Add(DicomTag.RecognitionCodeRETIRED, (object sender, DicomReaderEventArgs ea) => {
try {
string code = Encoding.ASCII.GetString(ea.Data.Data);
if (code == "ACR-NEMA 1.0")
{
_fileFormat = DicomFileFormat.ACRNEMA1;
}
else if (code == "ACR-NEMA 2.0")
{
_fileFormat = DicomFileFormat.ACRNEMA2;
}
} catch {
}
});
}
obs.Add(DicomTag.TransferSyntaxUID, (object sender, DicomReaderEventArgs ea) => {
try {
string uid = Encoding.ASCII.GetString(ea.Data.Data);
_syntax = DicomTransferSyntax.Parse(uid);
} catch {
}
});
_source.Endian = _syntax.Endian;
_reader.IsExplicitVR = _syntax.IsExplicitVR;
if (_fileFormat == DicomFileFormat.DICOM3NoFileMetaInfo)
{
_reader.BeginRead(_source, new DicomReaderMultiObserver(obs, _dataObserver), null, OnDatasetParseComplete, null);
}
else
{
_reader.BeginRead(_source, new DicomReaderMultiObserver(obs, _fmiObserver), FileMetaInfoStopTag, OnFileMetaInfoParseComplete, null);
}
} catch (Exception e) {
if (_exception == null)
{
_exception = e;
}
_result = DicomReaderResult.Error;
} finally {
if (_result != DicomReaderResult.Processing && _result != DicomReaderResult.Suspended)
{
_async.Set();
}
}
}
