ChannelBuffer header = dynamicBuffer(
channel.getConfig().getBufferFactory());
encodeInitialLine(header, m);
encodeHeaders(header, m);
header.writeByte(CR);
header.writeByte(LF);
ChannelBuffer content = m.getContent();
if (!content.readable()) {
return header; // no content
} else if (contentMustBeEmpty) {