private void ReadSequence(EndianBinaryReader reader, SpecificCharacterSet encoding, long start)
{
Tag lookahead = null;
// if we have somethign to read and we are not at the end of the stream
if (length != 0 && position != stream.Length)
{
// look ahead and see if we can find an item delimiter tag
lookahead = DataSet.PeekTag(reader, this.syntax);
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: Peek {1} in ReadSequence", stream.Position, lookahead.Description));
// as long as we have item tags
// TODO if we do not find an item tag that is a problem
while (lookahead.Equals(t.Item))
{
// position past the tag group and element
stream.Position += sizeof(ushort) + sizeof(ushort);
// find out the length of the item
uint count = reader.ReadUInt32();
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: Reading item of length={1}", stream.Position, (count == UInt32.MaxValue) ? "undefined" : count.ToString()));
Elements elements = new Elements();
items.Add(elements);
long place = stream.Position;
// call scan recursively, passing in the length limit which is the size of the
// entire item along with the sequence key name
long temp = (count != UInt32.MaxValue) ? (place + count) : -1;
place = DataSet.Scan(this, stream, elements, place, temp, UInt16.MaxValue, syntax, encoding);
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: Finished reading item", stream.Position));
if (stream.Position < stream.Length)
{
lookahead = DataSet.PeekTag(reader, this.syntax);
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: Peek {1} in ReadSequence", stream.Position, lookahead.Name));
}
// the next tag is either another item in the sequence, a sequence delimiter, or the next tag
// after the sequence. we only get the next tag if we are not at the end of the file and
// we have an undefined sequence length
if (length == UInt32.MaxValue)
{
if (lookahead.Equals(t.SequenceDelimitationItem))
{
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: undefined length, found {1}:{2}", stream.Position, lookahead.Description, lookahead.Name));
break;
}
}
else
{
if (stream.Position >= start + length)
{
break;
}
if (!lookahead.Equals(t.Item))
{
}
}
}
if (length == UInt32.MaxValue)
{
if (lookahead.Equals(t.SequenceDelimitationItem))
{
//System.Diagnostics.Debug.WriteLine(String.Format("0x{0:X8}:{0}: undefined length, found {1}:{2}", stream.Position, lookahead.Description, lookahead.Name));
// position stream beyond delimitation tag
stream.Position += sizeof(ushort) * 2;
// no need to check zero
int zero = reader.ReadInt32();
}
}
}
}
