/// <summary>
/// Decode messages from a payload and assign it a given kafka offset.
/// </summary>
/// <param name="reader">The reader</param>
/// <param name="messageSize">The size of the message, for Crc Hash calculation</param>
/// <param name="offset">The offset represting the log entry from kafka of this message.</param>
/// <param name="partitionId">The partition being read</param>
/// <returns>Enumerable representing stream of messages decoded from byte[].</returns>
/// <remarks>The return type is an Enumerable as the message could be a compressed message set.</remarks>
public static IImmutableList <Message> ReadMessage(this IKafkaReader reader, int messageSize, long offset, int partitionId = 0)
{
var crc = BitConverter.ToUInt32(reader.RawRead(4), 0);
var crcHash = BitConverter.ToUInt32(reader.CrcHash(messageSize - 4), 0);
if (crc != crcHash)
{
throw new CrcValidationException("Buffer did not match CRC validation.")
{
Crc = crc, CalculatedCrc = crcHash
}
}
;
var messageVersion = reader.ReadByte();
var attribute = reader.ReadByte();
DateTime?timestamp = null;
if (messageVersion >= 1)
{
var milliseconds = reader.ReadInt64();
if (milliseconds >= 0)
{
timestamp = milliseconds.FromUnixEpochMilliseconds();
}
}
var key = reader.ReadBytes();
var codec = (MessageCodec)(Message.AttributeMask & attribute);
switch (codec)
{
case MessageCodec.CodecNone: {
var value = reader.ReadBytes();
return(ImmutableList <Message> .Empty.Add(new Message(value, attribute, offset, partitionId, messageVersion, key, timestamp)));
}
case MessageCodec.CodecGzip: {
var messageLength = reader.ReadInt32();
var messageStream = new LimitedReadableStream(reader.BaseStream, messageLength);
using (var gzipReader = new BigEndianBinaryReader(messageStream.Unzip())) {
return(gzipReader.ReadMessages(partitionId));
}
}
default:
throw new NotSupportedException($"Codec type of {codec} is not supported.");
}
}