/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.directory.server.ntp.io;
import java.nio.ByteBuffer;
import org.apache.directory.server.ntp.messages.LeapIndicatorType;
import org.apache.directory.server.ntp.messages.ModeType;
import org.apache.directory.server.ntp.messages.NtpMessage;
import org.apache.directory.server.ntp.messages.NtpMessageModifier;
import org.apache.directory.server.ntp.messages.NtpTimeStamp;
import org.apache.directory.server.ntp.messages.ReferenceIdentifier;
import org.apache.directory.server.ntp.messages.StratumType;
/**
* @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
* @version $Rev: 547539 $, $Date: 2007-06-15 08:08:06 +0200 (Ven, 15 jui 2007) $
*/
public class NtpMessageDecoder
{
/**
* Decodes the {@link ByteBuffer} into an {@link NtpMessage}.
*
* @param request
* @return The {@link NtpMessage}.
*/
public NtpMessage decode( ByteBuffer request )
{
NtpMessageModifier modifier = new NtpMessageModifier();
byte header = request.get();
modifier.setLeapIndicator( parseLeapIndicator( header ) );
modifier.setVersionNumber( parseVersionNumber( header ) );
modifier.setMode( parseMode( header ) );
modifier.setStratum( parseStratum( request ) );
modifier.setPollInterval( parsePollInterval( request ) );
modifier.setPrecision( parsePrecision( request ) );
modifier.setRootDelay( parseRootDelay( request ) );
modifier.setRootDispersion( parseRootDispersion( request ) );
modifier.setReferenceIdentifier( parseReferenceIdentifier( request ) );
modifier.setReferenceTimestamp( new NtpTimeStamp( request ) );
modifier.setOriginateTimestamp( new NtpTimeStamp( request ) );
byte[] unneededBytes = new byte[8];
request.get( unneededBytes );
modifier.setReceiveTimestamp( new NtpTimeStamp() );
modifier.setTransmitTimestamp( new NtpTimeStamp( request ) );
return modifier.getNtpMessage();
}
private LeapIndicatorType parseLeapIndicator( byte header )
{
return LeapIndicatorType.getTypeByOrdinal( ( header & 0xc0 ) >>> 6 );
}
private int parseVersionNumber( byte header )
{
return ( header & 0x38 ) >>> 3;
}
private ModeType parseMode( byte header )
{
return ModeType.getTypeByOrdinal( header & 0x07 );
}
private StratumType parseStratum( ByteBuffer request )
{
return StratumType.getTypeByOrdinal( request.get() );
}
private byte parsePollInterval( ByteBuffer bytes )
{
return ( byte ) Math.round( Math.pow( 2, bytes.get() ) );
}
private byte parsePrecision( ByteBuffer bytes )
{
return ( byte ) ( 1000 * Math.pow( 2, bytes.get() ) );
}
private ReferenceIdentifier parseReferenceIdentifier( ByteBuffer request )
{
byte[] nextFourBytes = new byte[4];
request.get( nextFourBytes );
return ReferenceIdentifier.getTypeByName( new String( nextFourBytes ) );
}
private int parseRootDelay( ByteBuffer bytes )
{
int temp = 256 * ( 256 * ( 256 * bytes.get() + bytes.get() ) + bytes.get() ) + bytes.get();
return 1000 * ( temp / 0x10000 );
}
private int parseRootDispersion( ByteBuffer bytes )
{
int temp = 256 * ( 256 * ( 256 * bytes.get() + bytes.get() ) + bytes.get() ) + bytes.get();
return 1000 * ( temp / 0x10000 );
}
}