A single checksum calculation for multiple files
/*
* 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.
*/
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.zip.Adler32;
import java.util.zip.CheckedInputStream;
import java.util.zip.Checksum;
/**
* Perform a single checksum calculation for multiple files
*
* @author <a href="mailto:ate@douma.nu">Ate Douma</a>
* @author <a href="mailto:taylor@apache.org">David Sean Taylor </a>
* @version $Id$
*/
public class MultiFileChecksumHelper
{
public static long getChecksum(File[] files)
{
CheckedInputStream cis = null;
FileInputStream is = null;
Checksum checksum = new Adler32();
byte[] tempBuf = new byte[128];
for ( int i = 0; i < files.length && files[i] != null && files[i].exists() && files[i].isFile(); i++ )
{
try
{
is = new FileInputStream(files[i]);
cis = new CheckedInputStream(is, checksum);
while (cis.read(tempBuf) >= 0) {}
}
catch (Exception e)
{
throw new RuntimeException(e);
}
finally
{
if (cis != null)
{
try
{
cis.close();
}
catch (IOException ioe) {}
cis = null;
}
if (is != null)
{
try
{
is.close();
}
catch (IOException ioe) {}
is = null;
}
}
}
return checksum.getValue();
}
}
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