public StringBuilder appendTo(final StringBuilder builder)
    {
        if (null == buffer)
        {
            return builder;
        }

        final MessageHeaderDecoder decoder = new MessageHeaderDecoder();
        decoder.wrap(buffer, offset);

        return decoder.appendTo(builder);
    }
Message identifiers and length of message root.
sbe-tool/src/main/java/uk/co/real_logic/sbe/ir/generated/MessageHeaderEncoder.java