MD5Encoder.java

/*
 * Copyright 1999,2004 The Apache Software Foundation.
 * 
 * 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://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 com.ejie.x38.webdav.fromcatalina;

/**
 * Encode an MD5 digest into a String.
 * <p>
 * The 128 bit MD5 hash is converted into a 32 character long String. Each
 * character of the String is the hexadecimal representation of 4 bits of the
 * digest.
 * 
 * @author Remy Maucherat
 * @version $Revision: 1.2 $ $Date: 2008-08-05 07:38:45 $
 */

public final class MD5Encoder {

    // ----------------------------------------------------- Instance Variables

    private static final char[] HEXADECIMAL = { '0', '1', '2', '3', '4', '5',
            '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    // --------------------------------------------------------- Public Methods

    /**
     * Encodes the 128 bit (16 bytes) MD5 into a 32 character String.
     * 
     * @param binaryData
     *      Array containing the digest
     * @return Encoded MD5, or null if encoding failed
     */
    public String encode(byte[] binaryData) {

        if (binaryData.length != 16)
            return null;

        char[] buffer = new char[32];

        for (int i = 0; i < 16; i++) {
            int low = (int) (binaryData[i] & 0x0f);
            int high = (int) ((binaryData[i] & 0xf0) >> 4);
            buffer[i * 2] = HEXADECIMAL[high];
            buffer[i * 2 + 1] = HEXADECIMAL[low];
        }

        return new String(buffer);

    }

}