org.apache.mina.filter.codec

If the received IoBuffer is only a part of a message. decoders should cumulate received buffers to make a message complete or to postpone decoding until more buffers arrive.

Here is an example decoder that decodes CRLF terminated lines into Command objects:

 public class CrLfTerminatedCommandLineDecoder
 extends CumulativeProtocolDecoder {
 private Command parseCommand(IoBuffer in) {
 // Convert the bytes in the specified buffer to a
 // Command object.
 ...
 }
 protected boolean doDecode(
 IoSession session, IoBuffer in, ProtocolDecoderOutput out)
 throws Exception {
 // Remember the initial position.
 int start = in.position();
 // Now find the first CRLF in the buffer.
 byte previous = 0;
 while (in.hasRemaining()) {
 byte current = in.get();
 if (previous == '\r' && current == '\n') {
 // Remember the current position and limit.
 int position = in.position();
 int limit = in.limit();
 try {
 in.position(start);
 in.limit(position);
 // The bytes between in.position() and in.limit()
 // now contain a full CRLF terminated line.
 out.write(parseCommand(in.slice()));
 } finally {
 // Set the position to point right after the
 // detected line and set the limit to the old
 // one.
 in.position(position);
 in.limit(limit);
 }
 // Decoded one line; CumulativeProtocolDecoder will
 // call me again until I return false.