Digest.java

/**
 * Copyright 2005-2014 Restlet
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet.data;

import java.util.Arrays;

import org.restlet.representation.Representation;

/**
 * Describes a digest value and the digest algorithm used. Digests can have
 * several use cases such as ensuring the integrity of representations exchanges
 * between resources, or for authentication purpose.
 * 
 * @see Representation#getDigest()
 * @author Jerome Louvel
 */
public class Digest {

    /** Digest algorithm defined in RFC 1319. */
    public static final String ALGORITHM_MD2 = "MD2";

    /** Digest algorithm defined in RFC 1321. */
    public static final String ALGORITHM_MD5 = "MD5";

    /** No digest algorithm defined. */
    public static final String ALGORITHM_NONE = "NONE";

    /** Digest algorithm defined in Secure Hash Standard, NIST FIPS 180-1. */
    public static final String ALGORITHM_SHA_1 = "SHA-1";

    /** NIST approved digest algorithm from SHA-2 family. */
    public static final String ALGORITHM_SHA_256 = "SHA-256";

    /** NIST approved digest algorithm from SHA-2 family. */
    public static final String ALGORITHM_SHA_384 = "SHA-384";

    /** NIST approved digest algorithm from SHA-2 family. */
    public static final String ALGORITHM_SHA_512 = "SHA-512";

    /**
     * Digest algorithm for the HTTP DIGEST scheme. This is exactly the A1 value
     * specified in RFC2617 which is a MD5 hash of the user name, realm and
     * password, separated by a colon character.
     */
    public static final String ALGORITHM_HTTP_DIGEST = "HTTP-DIGEST-A1";

    /** The digest algorithm. */
    private final String algorithm;

    /** The digest value. */
    private final byte[] value;

    /**
     * Constructor using the MD5 algorithm by default.
     * 
     * @param value
     *            The digest value.
     */
    public Digest(byte[] value) {
        this(ALGORITHM_MD5, value);
    }

    /**
     * Constructor.
     * 
     * @param algorithm
     *            The digest algorithm.
     * @param value
     *            The digest value.
     */
    public Digest(String algorithm, byte[] value) {
        this.algorithm = algorithm;

        // In Java 6, use Arrays.copyOf.
        this.value = new byte[value.length];
        for (int i = 0; i < value.length; i++) {
            this.value[i] = value[i];
        }
    }

    @Override
    public boolean equals(Object obj) {
        boolean result = (obj instanceof Digest);

        if (result) {
            Digest d = (Digest) obj;
            result = getAlgorithm().equals(d.getAlgorithm());
            result = result && Arrays.equals(getValue(), d.getValue());
        }
        return result;
    }

    /**
     * Returns the digest algorithm.
     * 
     * @return The digest algorithm.
     */
    public String getAlgorithm() {
        return algorithm;
    }

    /**
     * Returns the digest value.
     * 
     * @return The digest value.
     */
    public byte[] getValue() {
        // In Java 6, use Arrays.copyOf.
        byte[] result = new byte[this.value.length];
        for (int i = 0; i < this.value.length; i++) {
            result[i] = this.value[i];
        }

        return result;
    }

    @Override
    public String toString() {
        return "Digest [algorithm=" + algorithm + ", value="
                + Arrays.toString(value) + "]";
    }

}