org.apache.shindig.common.util.HashUtil.java Source code

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Here is the source code for org.apache.shindig.common.util.HashUtil.java

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/*
 * 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.shindig.common.util;

import com.google.common.base.Preconditions;

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

/**
 * Routines for producing hashes.
 */
public final class HashUtil {
    private static final char[] HEX_CHARS = "0123456789abcdef".toCharArray();

    private HashUtil() {
    }

    /**
     * Produces a checksum for the given input data. Currently uses a hexified
     * message digest.
     *
     * @param data
     * @return The checksum.
     */
    public static String checksum(byte[] data) {
        byte[] hashBytes = getMessageDigest().digest(Preconditions.checkNotNull(data));
        char[] hex = new char[2 * hashBytes.length];

        // Convert to hex. possibly change to base64 in the future for smaller
        // signatures.

        int offset = 0;
        for (byte b : hashBytes) {
            hex[offset++] = HEX_CHARS[(b & 0xF0) >>> 4]; // upper 4 bits
            hex[offset++] = HEX_CHARS[(b & 0x0F)]; // lower 4 bits
        }
        return new String(hex);
    }

    /**
     * Produces a raw checksum for the given input data.  Currently uses a message digest
     *
     * @param data
     * @return The checksum.
     */
    public static String rawChecksum(byte[] data) {
        return new String(getMessageDigest().digest(Preconditions.checkNotNull(data)));
    }

    private static MessageDigest getMessageDigest() {
        MessageDigest md;
        try {
            md = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException noMD5) {
            try {
                md = MessageDigest.getInstance("SHA");
            } catch (NoSuchAlgorithmException noSha) {
                throw new RuntimeException("No suitable MessageDigest found!", noSha);
            }
        }
        return md;
    }
}