/// <summary>
/// Encodes a message object to byte[]
/// </summary>
/// <param name="message">Message data to encode.</param>
/// <returns>Encoded byte[] representation of the message object.</returns>
/// <remarks>
/// Format:
/// Crc (Int32), MagicByte (Byte), Attribute (Byte), Key (Byte[]), Value (Byte[])
/// </remarks>
public static byte[] EncodeMessage(Message message)
{
var body = new WriteByteStream();
body.Pack(new[] { message.MagicNumber },
new[] { message.Attribute },
message.Key.ToIntPrefixedBytes(),
message.Value.ToIntPrefixedBytes());
var crc = Crc32Provider.ComputeHash(body.Payload());
body.Prepend(crc);
return(body.Payload());
}
/// <summary>
/// Decode messages from a payload and assign it a given kafka offset.
/// </summary>
/// <param name="offset">The offset represting the log entry from kafka of this message.</param>
/// <param name="payload">The byte[] encode as a message from kafka.</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 IEnumerable <Message> DecodeMessage(long offset, byte[] payload)
{
var crc = payload.Take(4).ToArray();
var stream = new ReadByteStream(payload.Skip(4));
var hash = Crc32Provider.ComputeHash(stream.Payload);
if (crc.SequenceEqual(hash) == false)
{
throw new FailCrcCheckException("Payload did not match CRC validation.");
}
var message = new Message
{
Meta = new MessageMetadata {
Offset = offset
},
MagicNumber = stream.ReadByte(),
Attribute = stream.ReadByte(),
Key = stream.ReadIntPrefixedBytes()
};
var codec = (MessageCodec)(ProtocolConstants.AttributeCodeMask & message.Attribute);
switch (codec)
{
case MessageCodec.CodecNone:
message.Value = stream.ReadIntPrefixedBytes();
yield return(message);
break;
case MessageCodec.CodecGzip:
var gZipData = stream.ReadIntPrefixedBytes();
foreach (var m in DecodeMessageSet(Compression.Unzip(gZipData)))
{
yield return(m);
}
break;
default:
throw new NotSupportedException(string.Format("Codec type of {0} is not supported.", codec));
}
}
