Java Checksum Calculate generateChecksum(InputStream is)

Description

generate Checksum

License

Open Source License

Declaration

public static String generateChecksum(InputStream is) throws IOException 

Method Source Code

//package com.java2s;
/**//from   w ww .j a va2s.c  om
 * Project Wonderland
 *
 * Copyright (c) 2004-2009, Sun Microsystems, Inc., All Rights Reserved
 *
 * Redistributions in source code form must reproduce the above
 * copyright and this condition.
 *
 * The contents of this file are subject to the GNU General Public
 * License, Version 2 (the "License"); you may not use this file
 * except in compliance with the License. A copy of the License is
 * available at http://www.opensource.org/licenses/gpl-license.php.
 *
 * Sun designates this particular file as subject to the "Classpath" 
 * exception as provided by Sun in the License file that accompanied 
 * this code.
 */

import java.io.BufferedInputStream;

import java.io.IOException;
import java.io.InputStream;

import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Main {
    private static final String DEFAULT_ALGORITHM = "SHA-1";

    public static String generateChecksum(InputStream is) throws IOException {
        return generateChecksum(is, DEFAULT_ALGORITHM);
    }

    public static String generateChecksum(InputStream is, String checksumAlgorithm) throws IOException {
        MessageDigest digest;

        try {
            digest = MessageDigest.getInstance(checksumAlgorithm);
        } catch (NoSuchAlgorithmException nsae) {
            IOException ioe = new IOException("No such algorithm " + checksumAlgorithm);
            ioe.initCause(nsae);
            throw ioe;
        }

        byte[] buf = new byte[1024 * 1024];
        int bytesRead = 0;
        BufferedInputStream bis = new BufferedInputStream(is);
        InputStream in = new DigestInputStream(bis, digest);

        /* Read in the entire file */
        do {
            bytesRead = in.read(buf);
        } while (bytesRead != -1);
        in.close();

        /* Compute the checksum with the digest */
        byte[] byteChecksum = digest.digest();
        digest.reset();

        return toHexString(byteChecksum);
    }

    /**
     * Converts the checksum given as an array of bytes into a hex-encoded
     * string.
     *
     * @param bytes The checksum as an array of bytes
     * @return The checksum as a hex-encoded string
     */
    private static String toHexString(byte bytes[]) {
        StringBuffer ret = new StringBuffer();
        for (int i = 0; i < bytes.length; ++i) {
            ret.append(Integer.toHexString(0x0100 + (bytes[i] & 0x00FF)).substring(1));
        }
        return ret.toString();
    }
}

Related

1. checksum_icmpv6(byte pkt[])
2. checksumBytesToString(byte[] digestBytes)
3. checksumFile(File file)
4. checksumLength(int algorithmCode, int dataLength)
5. createChecksum(File file, String shaAlgo)
6. generateChecksum(String path, String flavor)
7. generateChecksum(String pType, String pInFile)
8. generateCheckSum(String string)
9. getChecksum(byte[] buffer, int offset, int length)