A
ProtocolDecoder that cumulates the content of received
buffers to a
cumulative buffer to help users implement decoders.
If the received
ByteBuffer 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(ByteBuffer in) {
// Convert the bytes in the specified buffer to a
// Command object.
...
}
protected boolean doDecode(IoSession session, ByteBuffer 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. So just
// return true until there are no more lines in the
// buffer.
return true;
}
previous = current;
}
// Could not find CRLF in the buffer. Reset the initial
// position to the one we recorded above.
in.position(start);
return false;
}
}