001package org.apache.maven.wagon.observers;
002
003/*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements.  See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership.  The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License.  You may obtain a copy of the License at
011 *
012 *   http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied.  See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022import org.apache.maven.wagon.events.TransferEvent;
023import org.apache.maven.wagon.events.TransferListener;
024
025import java.security.MessageDigest;
026import java.security.NoSuchAlgorithmException;
027
028/**
029 * TransferListeners which computes MD5 checksum on the fly when files are transfered.
030 *
031 * @author <a href="michal.maczka@dimatics.com">Michal Maczka</a>
032 *
033 */
034public class ChecksumObserver
035    implements TransferListener
036{
037    private MessageDigest digester = null;
038
039    private String actualChecksum;
040
041    public ChecksumObserver()
042        throws NoSuchAlgorithmException
043    {
044        this( "MD5" );
045    }
046
047    /**
048     * @param algorithm One of the algorithms supported by JDK: MD5, MD2 or SHA-1
049     */
050    public ChecksumObserver( String algorithm )
051        throws NoSuchAlgorithmException
052    {
053        digester = MessageDigest.getInstance( algorithm );
054    }
055
056    public void transferInitiated( TransferEvent transferEvent )
057    {
058        // This space left intentionally blank
059    }
060
061    /**
062     * @see org.apache.maven.wagon.events.TransferListener#transferStarted(org.apache.maven.wagon.events.TransferEvent)
063     */
064    public void transferStarted( TransferEvent transferEvent )
065    {
066        actualChecksum = null;
067
068        digester.reset();
069    }
070
071    /**
072     * @see org.apache.maven.wagon.events.TransferListener#transferProgress(org.apache.maven.wagon.events.TransferEvent, byte[], int)
073     */
074    public void transferProgress( TransferEvent transferEvent, byte[] buffer, int length )
075    {
076        digester.update( buffer, 0, length );
077    }
078
079    public void transferCompleted( TransferEvent transferEvent )
080    {
081        actualChecksum = encode( digester.digest() );
082    }
083
084    public void transferError( TransferEvent transferEvent )
085    {
086        digester.reset();
087
088        actualChecksum = null;
089    }
090
091    public void debug( String message )
092    {
093        // left intentionally blank
094    }
095
096    /**
097     * Returns md5 checksum which was computed during transfer
098     *
099     * @return
100     */
101    public String getActualChecksum()
102    {
103        return actualChecksum;
104    }
105
106    /**
107     * Encodes a 128 bit or 160-bit byte array into a String.
108     *
109     * @param binaryData Array containing the digest
110     * @return Encoded hex string, or null if encoding failed
111     */
112    protected String encode( byte[] binaryData )
113    {
114        if ( binaryData.length != 16 && binaryData.length != 20 )
115        {
116            int bitLength = binaryData.length * 8;
117            throw new IllegalArgumentException( "Unrecognised length for binary data: " + bitLength + " bits" );
118        }
119
120        StringBuilder retValue = new StringBuilder();
121
122        for ( byte b : binaryData )
123        {
124            String t = Integer.toHexString( b & 0xff );
125
126            if ( t.length() == 1 )
127            {
128                retValue.append( '0' ).append( t );
129            }
130            else
131            {
132                retValue.append( t );
133            }
134        }
135
136        return retValue.toString().trim();
137    }
138
139
140}