001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.transport.protocol;
018
019import java.nio.ByteBuffer;
020
021/**
022 *
023 *
024 */
025public class MqttProtocolVerifier implements ProtocolVerifier {
026
027    @Override
028    public boolean isProtocol(byte[] value) {
029       ByteBuffer buf = ByteBuffer.wrap(value);
030
031       if (!(buf.get() == 16 && validateRemainingLength(buf) && buf.get() == (byte) 0)) {
032           return false;
033       }
034       byte b = buf.get() ;
035       return ((b == 4 || b == 6) && (buf.get() == 77));
036    }
037
038    private boolean validateRemainingLength(ByteBuffer buffer) {
039       byte msb = (byte) 0b10000000;
040       for (byte i = 0; i < 4; i++) {
041          if ((buffer.get() & msb) != msb) {
042             return true;
043          }
044       }
045       return false;
046    }
047}