private IEnumerable <FetchResponse> DecodeFetchResponse(byte[] data)
{
var stream = new ReadByteStream(data);
var correlationId = stream.ReadInt();
var topicCount = stream.ReadInt();
for (int i = 0; i < topicCount; i++)
{
var topic = stream.ReadInt16String();
var partitionCount = stream.ReadInt();
for (int j = 0; j < partitionCount; j++)
{
var partitionId = stream.ReadInt();
var response = new FetchResponse
{
Topic = topic,
PartitionId = partitionId,
Error = stream.ReadInt16(),
HighWaterMark = stream.ReadLong()
};
//note: dont use initializer here as it breaks stream position.
response.Messages = Message.DecodeMessageSet(stream.ReadIntPrefixedBytes())
.Select(x => { x.Meta.PartitionId = partitionId; return(x); });
yield return(response);
}
}
}
/// <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));
}
}
/// <summary>
/// Decode a byte[] that represents a collection of messages.
/// </summary>
/// <param name="messageSet">The byte[] encode as a message set from kafka.</param>
/// <returns>Enumerable representing stream of messages decoded from byte[]</returns>
public static IEnumerable <Message> DecodeMessageSet(byte[] messageSet)
{
var stream = new ReadByteStream(messageSet);
while (stream.HasData)
{
var offset = stream.ReadLong();
foreach (var message in DecodeMessage(offset, stream.ReadIntPrefixedBytes()))
{
yield return(message);
}
}
}