public AppendRequest(String topic, Int32 partition, Message message)
: base(RequestType.AppendRequest)
{
Topic = topic;
Partition = partition;
Messages = new List<Message>(1) { message };
}
public void WriteMessage(Message message)
{
_writer.Write(message.MessageLength); // 4 bytes signed integer value
_writer.Write((byte) 1); // 1 byte "magic" number. Currently it is always '1'.
_writer.Write(message.Crc); // 4 bytes CRC32 hash
_writer.Write(message.Payload); // Actual message data
}
/// <summary>
/// Message that was correctly read, or null if end of stream found
/// </summary>
public Message ReadMessage()
{
try
{
// If this is the end of stream, return null
if (_stream.Position == _stream.Length)
return null;
// Can we read 4 bytes?
if (_stream.Position + 4 /* size of message length field */ > _stream.Length)
return null;
// Read 4 bytes that contains message length
var messageLength = _reader.ReadInt32();
// If message length less or equlal zero - we probably read all messages
if (messageLength <= 0)
return null;
// Can we read messageLength bytes?
if (_stream.Position + messageLength > _stream.Length)
return null;
var message = new Message();
message.Magic = _reader.ReadByte();
message.Crc = _reader.ReadBytes(4);
message.Payload = _reader.ReadBytes(Message.CalculatePayloadLength(messageLength));
// Validate message content
message.Validate();
return message;
}
catch (EndOfStreamException)
{
return null;
}
}
/// <summary>
/// Factory method for creating message with payload
/// </summary>
public static Message CreateMessage(byte[] payload)
{
using (var crc32 = new Crc32())
{
var message = new Message();
message.Magic = 1;
message.Payload = payload;
message.Crc = crc32.ComputeHash(payload);
return message;
}
}
