/// <summary>
/// ChangeMode
/// </summary>
/// <param name="newMode"></param>
/// <remarks>Does not update Position of _current for change to ReadPassThroughMode.</remarks>
private void ChangeMode(Mode newMode)
{
// ignore redundant calls (allowing these actually simplifies the logic in SetLength)
if (newMode == _mode)
{
return;
}
// every state change requires this logic
if (_current != null)
{
_current.Close();
_dirtyForClosing = false;
_dirtyForFlushing = false;
}
// set the new mode - must be done before the call to Seek
_mode = newMode;
switch (newMode)
{
case Mode.Start:
{
_current = null;
_baseStream.Position = 0;
break;
}
case Mode.ReadPassThrough:
case Mode.WritePassThrough:
{
Debug.Assert(_baseStream.Position == 0);
// create the appropriate DeflateStream
_current = new DeflateStream(_baseStream,
newMode == Mode.WritePassThrough ? CompressionMode.Compress : CompressionMode.Decompress,
true);
break;
}
case Mode.Emulation:
{
// Create emulation stream. Use a MemoryStream for local caching.
// Do not change this logic for RM cases because the data is "in the clear" and must
// not be persisted in a vulnerable location.
SparseMemoryStream memStream = new SparseMemoryStream(_lowWaterMark, _highWaterMark);
_current = new CompressEmulationStream(_baseStream, memStream, _position, new DeflateEmulationTransform());
// verify and set length
UpdateUncompressedDataLength(_current.Length);
break;
}
case Mode.Disposed: break;
default:
Debug.Assert(false, "Illegal state for CompressStream - logic error"); break;
}
}
/// <summary>
/// ChangeMode
/// </summary>
/// <param name="newMode"></param>
/// <remarks>Does not update Position of _current for change to ReadPassThroughMode.</remarks>
private void ChangeMode(Mode newMode)
{
// ignore redundant calls (allowing these actually simplifies the logic in SetLength)
if (newMode == _mode)
return;
// every state change requires this logic
if (_current != null)
{
_current.Close();
_dirtyForClosing = false;
_dirtyForFlushing = false;
}
// set the new mode - must be done before the call to Seek
_mode = newMode;
switch (newMode)
{
case Mode.Start:
{
_current = null;
_baseStream.Position = 0;
break;
}
case Mode.ReadPassThrough:
case Mode.WritePassThrough:
{
Debug.Assert(_baseStream.Position == 0);
// create the appropriate DeflateStream
_current = new DeflateStream(_baseStream,
newMode == Mode.WritePassThrough ? CompressionMode.Compress : CompressionMode.Decompress,
true);
break;
}
case Mode.Emulation:
{
// Create emulation stream. Use a MemoryStream for local caching.
// Do not change this logic for RM cases because the data is "in the clear" and must
// not be persisted in a vulnerable location.
SparseMemoryStream memStream = new SparseMemoryStream(_lowWaterMark, _highWaterMark);
_current = new CompressEmulationStream(_baseStream, memStream, _position, new DeflateEmulationTransform());
// verify and set length
UpdateUncompressedDataLength(_current.Length);
break;
}
case Mode.Disposed: break;
default:
Debug.Assert(false, "Illegal state for CompressStream - logic error"); break;
}
}
IDataTransform.GetTransformedStream(
Stream encodedStream,
IDictionary transformContext
)
{
Stream tempStream = new SparseMemoryStream(_lowWaterMark, _highWaterMark);
tempStream = new CompressEmulationStream(encodedStream, tempStream, 0, new CompoundFileDeflateTransform());
// return a VersionedStream that works with the VersionedStreamOwner
// to verify/update our FormatVersion info
return new VersionedStream(tempStream, _versionedStreamOwner);
}
