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Support Seek #8

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Support Seek #8

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41 changes: 39 additions & 2 deletions src/CombinationStream-Net20/CombinationStream.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ internal class CombinationStream : Stream
{
private readonly IList<Stream> _streams;
private readonly IList<int> _streamsToDispose;
private readonly IList<long> _streamsStartPos;
private int _currentStreamIndex;
private Stream _currentStream;
private long _length = -1;
Expand All @@ -52,6 +53,14 @@ public CombinationStream(IList<Stream> streams, IList<int> streamsToDispose)
_streamsToDispose = streamsToDispose;
if (streams.Count > 0)
_currentStream = streams[_currentStreamIndex++];

_streamsStartPos = new List<long>(streams.Count);
long pos = 0;
foreach (var strm in streams)
{
_streamsStartPos.Add(pos);
pos += strm.Length;
}
}

public IList<Stream> InternalStreams { get { return _streams; } }
Expand All @@ -64,7 +73,35 @@ public override void Flush()

public override long Seek(long offset, SeekOrigin origin)
{
throw new InvalidOperationException("Stream is not seekable.");
long pos = 0;
switch (origin)
{
case SeekOrigin.Begin:
pos = offset;
break;
case SeekOrigin.Current:
pos = this.Position + offset;
break;
case SeekOrigin.End:
pos = Length + offset;
break;
}
int idx = 0;
while (idx+1 < _streamsStartPos.Count)
{
if (_streamsStartPos[idx + 1] > pos)
{
break;
}
idx++;
}

_currentStreamIndex = idx;
_currentStream = _streams[_currentStreamIndex];
_currentStream.Seek(pos - _streamsStartPos[idx], SeekOrigin.Begin);
_postion = pos;
return _postion;
//throw new InvalidOperationException("Stream is not seekable.");
}

public override void SetLength(long value)
Expand Down Expand Up @@ -286,7 +323,7 @@ public override bool CanRead

public override bool CanSeek
{
get { return false; }
get { return true; }
}

public override bool CanWrite
Expand Down