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Ant example source code file (ChecksumAlgorithm.java)
This example Ant source code file (ChecksumAlgorithm.java) is included in the DevDaily.com
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The ChecksumAlgorithm.java source code
/*
* 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.tools.ant.types.selectors.modifiedselector;
import java.util.zip.Checksum;
import java.util.zip.CRC32;
import java.util.zip.Adler32;
import java.util.zip.CheckedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.BufferedInputStream;
import java.security.NoSuchAlgorithmException;
import org.apache.tools.ant.BuildException;
/**
* Computes a 'checksum' for the content of file using
* java.util.zip.CRC32 and java.util.zip.Adler32.
* Use of this algorithm doesn't require any additional nested <param>s.
* Supported <param>s are:
* <table>
* <tr>
* <th>name| values | description | required |
* </tr>
* <tr>
* <td> algorithm.algorithm |
* <td> ADLER | CRC ( default )
* <td> name of the algorithm the checksum should use
* <td> no, defaults to CRC
* </tr>
* </table>
*
* @version 2004-06-17
* @since Ant 1.7
*/
public class ChecksumAlgorithm implements Algorithm {
// ----- member variables -----
/**
* Checksum algorithm to be used.
*/
private String algorithm = "CRC";
/**
* Checksum interface instance
*/
private Checksum checksum = null;
// ----- Algorithm-Configuration -----
/**
* Specifies the algorithm to be used to compute the checksum.
* Defaults to "CRC". Other popular algorithms like "ADLER" may be used as well.
* @param algorithm the digest algorithm to use
*/
public void setAlgorithm(String algorithm) {
this.algorithm = algorithm;
}
/** Initialize the checksum interface. */
public void initChecksum() {
if (checksum != null) {
return;
}
if ("CRC".equalsIgnoreCase(algorithm)) {
checksum = new CRC32();
} else if ("ADLER".equalsIgnoreCase(algorithm)) {
checksum = new Adler32();
} else {
throw new BuildException(new NoSuchAlgorithmException());
}
}
// ----- Logic -----
/**
* This algorithm supports only CRC and Adler.
* @return <i>true if all is ok, otherwise false.
*/
public boolean isValid() {
return "CRC".equalsIgnoreCase(algorithm) || "ADLER".equalsIgnoreCase(algorithm);
}
/**
* Computes a value for a file content with the specified checksum algorithm.
* @param file File object for which the value should be evaluated.
* @return The value for that file
*/
public String getValue(File file) {
initChecksum();
String rval = null;
try {
if (file.canRead()) {
checksum.reset();
FileInputStream fis = new FileInputStream(file);
CheckedInputStream check = new CheckedInputStream(fis, checksum);
BufferedInputStream in = new BufferedInputStream(check);
while (in.read() != -1) {
// Read the file
}
rval = Long.toString(check.getChecksum().getValue());
in.close();
}
} catch (Exception e) {
rval = null;
}
return rval;
}
/**
* Override Object.toString().
* @return some information about this algorithm.
*/
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append("<ChecksumAlgorithm:");
buf.append("algorithm=").append(algorithm);
buf.append(">");
return buf.toString();
}
}
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