001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied. See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 *
019 */
020
021 package org.apache.directory.server.ntp.io;
022
023
024 import java.nio.ByteBuffer;
025
026 import org.apache.directory.server.ntp.messages.LeapIndicatorType;
027 import org.apache.directory.server.ntp.messages.ModeType;
028 import org.apache.directory.server.ntp.messages.NtpMessage;
029 import org.apache.directory.server.ntp.messages.NtpMessageModifier;
030 import org.apache.directory.server.ntp.messages.NtpTimeStamp;
031 import org.apache.directory.server.ntp.messages.ReferenceIdentifier;
032 import org.apache.directory.server.ntp.messages.StratumType;
033
034
035 /**
036 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
037 * @version $Rev: 547539 $, $Date: 2007-06-15 09:08:06 +0300 (Fri, 15 Jun 2007) $
038 */
039 public class NtpMessageDecoder
040 {
041 /**
042 * Decodes the {@link ByteBuffer} into an {@link NtpMessage}.
043 *
044 * @param request
045 * @return The {@link NtpMessage}.
046 */
047 public NtpMessage decode( ByteBuffer request )
048 {
049 NtpMessageModifier modifier = new NtpMessageModifier();
050
051 byte header = request.get();
052 modifier.setLeapIndicator( parseLeapIndicator( header ) );
053 modifier.setVersionNumber( parseVersionNumber( header ) );
054 modifier.setMode( parseMode( header ) );
055 modifier.setStratum( parseStratum( request ) );
056 modifier.setPollInterval( parsePollInterval( request ) );
057 modifier.setPrecision( parsePrecision( request ) );
058 modifier.setRootDelay( parseRootDelay( request ) );
059 modifier.setRootDispersion( parseRootDispersion( request ) );
060 modifier.setReferenceIdentifier( parseReferenceIdentifier( request ) );
061 modifier.setReferenceTimestamp( new NtpTimeStamp( request ) );
062 modifier.setOriginateTimestamp( new NtpTimeStamp( request ) );
063
064 byte[] unneededBytes = new byte[8];
065 request.get( unneededBytes );
066
067 modifier.setReceiveTimestamp( new NtpTimeStamp() );
068 modifier.setTransmitTimestamp( new NtpTimeStamp( request ) );
069
070 return modifier.getNtpMessage();
071 }
072
073
074 private LeapIndicatorType parseLeapIndicator( byte header )
075 {
076 return LeapIndicatorType.getTypeByOrdinal( ( header & 0xc0 ) >>> 6 );
077 }
078
079
080 private int parseVersionNumber( byte header )
081 {
082 return ( header & 0x38 ) >>> 3;
083 }
084
085
086 private ModeType parseMode( byte header )
087 {
088 return ModeType.getTypeByOrdinal( header & 0x07 );
089 }
090
091
092 private StratumType parseStratum( ByteBuffer request )
093 {
094 return StratumType.getTypeByOrdinal( request.get() );
095 }
096
097
098 private byte parsePollInterval( ByteBuffer bytes )
099 {
100 return ( byte ) Math.round( Math.pow( 2, bytes.get() ) );
101 }
102
103
104 private byte parsePrecision( ByteBuffer bytes )
105 {
106 return ( byte ) ( 1000 * Math.pow( 2, bytes.get() ) );
107 }
108
109
110 private ReferenceIdentifier parseReferenceIdentifier( ByteBuffer request )
111 {
112 byte[] nextFourBytes = new byte[4];
113 request.get( nextFourBytes );
114 return ReferenceIdentifier.getTypeByName( new String( nextFourBytes ) );
115 }
116
117
118 private int parseRootDelay( ByteBuffer bytes )
119 {
120 int temp = 256 * ( 256 * ( 256 * bytes.get() + bytes.get() ) + bytes.get() ) + bytes.get();
121 return 1000 * ( temp / 0x10000 );
122 }
123
124
125 private int parseRootDispersion( ByteBuffer bytes )
126 {
127 int temp = 256 * ( 256 * ( 256 * bytes.get() + bytes.get() ) + bytes.get() ) + bytes.get();
128 return 1000 * ( temp / 0x10000 );
129 }
130 }