public ElementInfo Next() {
if((lastElementPos != ~VIntConsts.UNKNOWN_LENGTH && nextElementPos >= lastElementPos) || nextElementPos == ~VIntConsts.UNKNOWN_LENGTH || dataSrc.EOF) return null;
if(dataSrc.Position != nextElementPos) dataSrc.Position = nextElementPos;
ElementInfo elemInfo;
var docElementId = dataSrc.ReadIdentifier();
var vintPos = dataSrc.Position;
var dataLength = dataSrc.ReadVInt();
var dataPos = dataSrc.Position;
var isDocElementInvalid = docElementId < 0 && (~docElementId & VIntConsts.ERROR) != 0;
var isDataLengthInvalid = dataLength < 0 && (~dataLength & VIntConsts.ERROR) != 0;
var isOutOfBounds = lastElementPos != ~VIntConsts.UNKNOWN_LENGTH && dataPos + dataLength > lastElementPos;
if(isDocElementInvalid || isDataLengthInvalid || isOutOfBounds) {
elemInfo = new ElementInfo(EBMLDocElement.Unknown, nextElementPos, vintPos, dataPos, 0);
dataSrc.SyncTo(bytePatterns, lastElementPos);
nextElementPos = dataSrc.Position;
return elemInfo;
}
var docElem = docType.RetrieveDocElement(docElementId);
elemInfo = new ElementInfo(docElem, nextElementPos, vintPos, dataPos, dataLength < 0 ? default(Int64?) : dataLength);
nextElementPos = dataLength < 0 ? ~VIntConsts.UNKNOWN_LENGTH : dataPos + dataLength;
//Trace.WriteLine(elemInfo.ToDetailedString());
return elemInfo;
}
public Object RetrieveValue(ElementInfo elem) {
if(elem == null) throw new ArgumentNullException("elem");
if(!elem.DataLength.HasValue) throw new InvalidOperationException("Cannot retrieve value: Length unknown");
if(elem.DataLength.Value == 0) return new byte[0];
if(dataSrc.Position != elem.DataPos) throw new InvalidOperationException("Cannot retrieve value: Current position doesn't match element data position");
Int64 offset;
var valueData = dataSrc.GetData(elem.DataLength.Value, out offset);
return docType.RetrieveValue(elem.DocElement, valueData, offset, elem.DataLength.Value);
}
public ElementInfo WriteElement(EBMLDocElement elem, Stream data)
{
Int64 idPos = dataSrc.Position;
dataSrc.WriteIdentifier(elem.Id);
Int64 vIntPos = dataSrc.Position;
dataSrc.WriteFakeVInt(8);
Int64 dataPos = dataSrc.Position;
dataSrc.Write(data);
var elemInfo = new ElementInfo(elem, idPos, vIntPos, dataPos, null);
UpdateElementLength(elemInfo);
return elemInfo;
}
private void UpdateElementLength(ElementInfo elemInfo)
{
var currentPos = dataSrc.Position;
var dataLength = currentPos - elemInfo.DataPos;
elemInfo.DataLength = dataLength;
dataSrc.Position = elemInfo.VIntPos;
dataSrc.WriteVInt(dataLength, 8);
dataSrc.Position = currentPos;
}
public IDisposable EnterElement(ElementInfo elemInfo) {
var disposable = new PreviousState {
NextElementPos = nextElementPos,
LastElementPos = lastElementPos
};
disposable.Disposed += (s, e) => {
var d = (PreviousState)s;
if(nextElementPos < d.LastElementPos) nextElementPos = d.NextElementPos;
lastElementPos = d.LastElementPos;
};
nextElementPos = elemInfo.DataPos;
lastElementPos = elemInfo.DataLength.HasValue ? elemInfo.DataPos + elemInfo.DataLength.Value : ~VIntConsts.UNKNOWN_LENGTH;
return disposable;
}
