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/*
 * Copyright 2012-2013 Amazon Technologies, Inc.
 *
 * Portions copyright 2006-2009 James Murty. Please see LICENSE.txt
 * for applicable license terms and NOTICE.txt for applicable notices.
 *
 * Licensed 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://aws.amazon.com/apache2.0
 *
 * This file 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 com.sinacloud.scs.util;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Utility methods for computing MD5 sums.
 */
public class Md5Utils {

    /**
     * Computes the MD5 hash of the data in the given input stream and returns
     * it as an array of bytes.
     */
    public static byte[] computeMD5Hash(InputStream is) throws NoSuchAlgorithmException, IOException {
        BufferedInputStream bis = new BufferedInputStream(is);
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("MD5");
            byte[] buffer = new byte[16384];
            int bytesRead = -1;
            while ( (bytesRead = bis.read(buffer, 0, buffer.length)) != -1 ) {
                messageDigest.update(buffer, 0, bytesRead);
            }
            return messageDigest.digest();
        } finally {
            try {
                bis.close();
            } catch ( Exception e ) {
                System.err.println("Unable to close input stream of hash candidate: " + e);
            }
        }
    }

    /**
     * Computes the MD5 hash of the given data and returns it as an array of
     * bytes.
     */
    public static byte[] computeMD5Hash(byte[] data) throws NoSuchAlgorithmException, IOException {
        return computeMD5Hash(new ByteArrayInputStream(data));
    }
}