IEnumerable <WebSocketsFrame> IExtension.ApplyOutgoing(NetContext context, WebSocketConnection connection, WebSocketsFrame frame)
{
if (!frame.IsControlFrame && frame.PayloadLength > parent.compressMessagesLargerThanBytes)
{
if (frame.Reserved1)
{
throw new InvalidOperationException("Reserved1 flag is already set; extension conflict?");
}
int headerBytes = 0;
if (outbound == null)
{
outbound = new ZStream();
const int BITS = 12; // 4096 byte outbound buffer (instead of full 32k=15)
outbound.deflateInit(zlibConst.Z_BEST_COMPRESSION, BITS);
headerBytes = 2;
}
BufferStream tmp = null;
var payload = frame.Payload;
payload.Position = 0;
byte[] inBuffer = null, outBuffer = null;
try
{
inBuffer = context.GetBuffer();
outBuffer = context.GetBuffer();
tmp = new BufferStream(context, 0);
outbound.next_out = outBuffer;
outbound.next_in = inBuffer;
int remaining = frame.PayloadLength;
while (remaining > 0)
{
int readCount = payload.Read(inBuffer, 0, inBuffer.Length);
if (readCount <= 0)
{
break;
}
remaining -= readCount;
outbound.next_in_index = 0;
outbound.avail_in = readCount;
do
{
outbound.next_out_index = 0;
outbound.avail_out = outBuffer.Length;
long priorOut = outbound.total_out;
int err = outbound.deflate(remaining == 0 ? zlibConst.Z_SYNC_FLUSH : zlibConst.Z_NO_FLUSH);
if (err != zlibConst.Z_OK && err != zlibConst.Z_STREAM_END)
{
throw new ZStreamException("deflating: " + outbound.msg);
}
int outCount = (int)(outbound.total_out - priorOut);
if (outCount > 0)
{
if (headerBytes == 0)
{
tmp.Write(outBuffer, 0, outCount);
}
else
{
if (outCount < headerBytes)
{
throw new InvalidOperationException("Failed to write entire header");
}
// check the generated header meets our expectations
// CMF is very specific - CM must be 8, and CINFO must be <=7 (for 32k window)
if ((outBuffer[0] & 15) != 8)
{
throw new InvalidOperationException("Zlib CM header was incorrect");
}
if ((outBuffer[0] & 128) != 0) // if msb set, is > 7 - invalid
{
throw new InvalidOperationException("Zlib CINFO header was incorrect");
}
// FLG is less important; FCHECK is irrelevent, FLEVEL doesn't matter; but
// FDICT must be zero, to ensure that we aren't expecting a an initialization dictionary
if ((outBuffer[1] & 32) != 0)
{
throw new InvalidOperationException("Zlib FLG.FDICT header was set (must not be)");
}
// skip the header, and write anything else
outCount -= headerBytes;
if (outCount > 0)
{
tmp.Write(outBuffer, headerBytes, outCount);
}
headerBytes = 0; // all written now
}
}
} while (outbound.avail_in > 0 || outbound.avail_out == 0);
}
if (remaining != 0)
{
throw new EndOfStreamException();
}
if (headerBytes != 0)
{
throw new InvalidOperationException("Zlib header was not written");
}
// verify the last 4 bytes, then drop them
tmp.Position = tmp.Length - 4;
NetContext.Fill(tmp, outBuffer, 4);
if (!(outBuffer[0] == 0x00 && outBuffer[1] == 0x00 && outBuffer[2] == 0xFF && outBuffer[3] == 0xFF))
{
throw new InvalidOperationException("expectation failed: 0000FFFF in the tail");
}
if (parent.disableContextTakeover && tmp.Length >= frame.PayloadLength)
{ // compressing it didn't do anything useful; since we're going to discard
// the compression context, we might as well stick with the original data
payload.Position = 0;
payload = null; // so that it doesn't get disposed
}
else
{
// set our final output
tmp.Position = 0;
tmp.SetLength(tmp.Length - 4);
long bytesSaved = frame.PayloadLength - tmp.Length;
frame.Payload = tmp;
frame.PayloadLength = (int)tmp.Length;
frame.Reserved1 = true;
tmp = payload as BufferStream;
parent.RegisterOutboundBytesSaved(bytesSaved);
}
}
#if DEBUG
catch (Exception ex)
{
Debug.WriteLine(ex);
throw;
}
#endif
finally
{
if (outbound != null)
{
outbound.next_out = null;
outbound.next_in = null;
}
if (tmp != null)
{
tmp.Dispose();
}
if (inBuffer != null)
{
context.Recycle(inBuffer);
}
if (outBuffer != null)
{
context.Recycle(outBuffer);
}
if (parent.disableContextTakeover)
{
ClearContext(false, true);
}
}
}
yield return(frame);
}
