static MessageData Compress(CompressionType compressionType, IEnumerable <MessageData> messages)
{
if (compressed == null)
{
compressed = new MemoryStream();
}
else
{
compressed.Position = 0;
compressed.SetLength(0);
}
switch (compressionType)
{
case CompressionType.Gzip:
{
var gzip = new GZipStream(compressed, CompressionLevel.Optimal, true);
Write(gzip, messages);
gzip.Close();
break;
}
case CompressionType.Snappy:
{
if (_snappyCompressedBuffer == null)
{
KafkaSnappyStream.AllocateBuffers(out _snappyUncompressedBuffer, out _snappyCompressedBuffer);
}
var snappy = new KafkaSnappyStream(compressed, CompressionStreamMode.Compress, _snappyUncompressedBuffer, _snappyCompressedBuffer);
Write(snappy, messages);
snappy.Close();
break;
}
case CompressionType.Lz4:
{
var lz4 = new Lz4KafkaStream(compressed, CompressionStreamMode.Compress);
Write(lz4, messages);
lz4.Close();
break;
}
default:
throw new NotImplementedException($"Compression '{compressionType}' is not implemented");
}
var buff = new ArraySegment <byte>(compressed.GetBuffer(), 0, (int)compressed.Length);
return(new MessageData {
Key = null, Value = buff
});
}
//N.B., MessageSets are not preceded by an int32 like other array elements in the protocol.
//
//MessageSet => [Offset MessageSize Message]
// Offset => int64
// MessageSize => int32
//
//Message => Crc MagicByte Attributes Key Value
// Crc => int32
// MagicByte => int8
// Attributes => int8
// Key => bytes
// Value => bytes
private static IEnumerable <Message> ReadMessageSet(Stream stream, int messageSetSize)
{
// "As an optimization the server is allowed to return a partial message at the end of the message set.
// Clients should handle this case"
var remainingMessageSetBytes = messageSetSize;
while (remainingMessageSetBytes > 0)
{
// we need at least be able to read offset and messageSize
if (remainingMessageSetBytes < 8 + 4)
{
// not enough bytes left. This is a partial message. Skip to the end of the message set.
stream.Position += remainingMessageSetBytes;
yield break;
}
var offset = BigEndianConverter.ReadInt64(stream);
var messageSize = BigEndianConverter.ReadInt32(stream);
// we took 12 bytes there, check again that we have a full message.
remainingMessageSetBytes -= 8 + 4;
if (remainingMessageSetBytes < messageSize)
{
// not enough bytes left. This is a partial message. Skip to the end of the message set.
stream.Position += remainingMessageSetBytes;
yield break;
}
// Message
var crc = (uint)BigEndianConverter.ReadInt32(stream);
byte magic = (byte)stream.ReadByte();
if (magic != 0)
{
throw new BrokerException("Invalid kafks message magic"); // TODO: use special exception for data corruption
}
var attributes = (byte)stream.ReadByte();
var compression = ParseCompression(attributes);
var key = ReadByteArray(stream);
var value = ReadByteArray(stream);
if (compression == CompressionType.None)
{
var msg = new Message();
msg.Key = key;
msg.Value = value;
msg.Offset = offset;
var computedCrc = Crc32.Update(magic);
computedCrc = Crc32.Update(attributes, computedCrc);
if (key == null)
{
computedCrc = Crc32.Update(_minusOne32, computedCrc);
}
else
{
computedCrc = Crc32.Update(key.Length, computedCrc);
computedCrc = Crc32.Update(key, computedCrc);
}
if (value == null)
{
computedCrc = Crc32.Update(_minusOne32);
}
else
{
computedCrc = Crc32.Update(value.Length, computedCrc);
computedCrc = Crc32.Update(value, computedCrc);
}
computedCrc = Crc32.GetHash(computedCrc);
if (computedCrc != crc)
{
throw new BrokerException(string.Format("Corrupt message: Crc does not match. Caclulated {0} but got {1}", computedCrc, crc));
}
yield return(msg);
}
else if (compression == CompressionType.Gzip)
{
var decompressedStream = new MemoryStream();
new GZipStream(new MemoryStream(value), CompressionMode.Decompress).CopyTo(decompressedStream);
decompressedStream.Seek(0, SeekOrigin.Begin);
// Recursion
var innerMessages = ReadMessageSet(decompressedStream, (int)decompressedStream.Length);
foreach (var innerMessage in innerMessages)
{
yield return(innerMessage);
}
}
else if (compression == CompressionType.Lz4)
{
using (var lz4Stream = new Lz4KafkaStream(new MemoryStream(value), CompressionStreamMode.Decompress))
{
var decompressed = new MemoryStream();
lz4Stream.CopyTo(decompressed);
decompressed.Seek(0, SeekOrigin.Begin);
var decompressedMessages = ReadMessageSet(decompressed, (int)decompressed.Length);
foreach (var msg in decompressedMessages)
{
yield return(msg);
}
}
}
else if (compression == CompressionType.Snappy)
{
if (_snappyCompressedBuffer == null)
{
KafkaSnappyStream.AllocateBuffers(out _snappyUncompressedBuffer, out _snappyCompressedBuffer);
}
using (var snappyStream = new KafkaSnappyStream(new MemoryStream(value), CompressionStreamMode.Decompress, _snappyUncompressedBuffer, _snappyCompressedBuffer))
{
var decompressed = new MemoryStream();
snappyStream.CopyTo(decompressed);
decompressed.Seek(0, SeekOrigin.Begin);
var decompressedMessages = ReadMessageSet(decompressed, (int)decompressed.Length);
foreach (var msg in decompressedMessages)
{
yield return(msg);
}
}
}
else
{
throw new BrokerException(string.Format("Unknown compression type: {0}", attributes & 3));
}
// subtract messageSize of that message from remaining bytes
remainingMessageSetBytes -= messageSize;
}
}