/// <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>
/// <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)
{
var crc = reader.ReadUInt32();
var crcHash = reader.ReadCrc(messageSize - 4);
if (crc != crcHash)
{
throw new CrcValidationException(crc, crcHash);
}
var messageVersion = reader.ReadByte();
var attribute = reader.ReadByte();
DateTimeOffset?timestamp = null;
if (messageVersion >= 1)
{
var milliseconds = reader.ReadInt64();
if (milliseconds >= 0)
{
timestamp = DateTimeOffset.FromUnixTimeMilliseconds(milliseconds);
}
}
var key = reader.ReadBytes();
var value = reader.ReadBytes();
var codec = (MessageCodec)(Message.CodecMask & attribute);
if (codec == MessageCodec.None)
{
return(ImmutableList <Message> .Empty.Add(new Message(value, key, attribute, offset, messageVersion, timestamp)));
}
var uncompressedBytes = value.ToUncompressed(codec);
using (var messageSetReader = new KafkaReader(uncompressedBytes)) {
return(messageSetReader.ReadMessages(codec));
}
}