/*
 *  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 javax.crypto.spec;

import java.security.InvalidKeyException;
import java.security.spec.KeySpec;

/**
 * The key specification for a triple-DES (DES-EDE) key.
 */
public class DESedeKeySpec implements KeySpec {

    /**
     * The length of a DES-EDE key in bytes.
     */
    public static final int DES_EDE_KEY_LEN = 24;

    private final byte[] key;

    /**
     * Creates a new <code>DESedeKeySpec</code> instance from the first 24 (
     * {@link #DES_EDE_KEY_LEN}) bytes of the specified key data.
     *
     * @param key
     *            the key data.
     * @throws InvalidKeyException
     *             if the length of the key data is less than 24.
     * @throws NullPointerException
     *             if the key data is null.
     */
    public DESedeKeySpec(byte[] key) throws InvalidKeyException {
        if (key == null) {
            throw new NullPointerException("key == null");
        }
        if (key.length < DES_EDE_KEY_LEN) {
            throw new InvalidKeyException();
        }
        this.key = new byte[DES_EDE_KEY_LEN];
        System.arraycopy(key, 0, this.key, 0, DES_EDE_KEY_LEN);
    }

    /**
     * Creates a new <code>DESedeKeySpec</code> instance from the first 24 (
     * {@link #DES_EDE_KEY_LEN} ) bytes of the specified key data starting at
     * <code>offset</code>.
     *
     * @param key
     *            the key data
     * @param offset
     *            the offset to start at.
     * @throws InvalidKeyException
     *             if the length of the key data starting at offset is less than
     *             24.
     * @throws NullPointerException
     *             if the key data is null.
     */
    public DESedeKeySpec(byte[] key, int offset) throws InvalidKeyException {
        if (key == null) {
            throw new NullPointerException("key == null");
        }
        if (key.length - offset < DES_EDE_KEY_LEN) {
            throw new InvalidKeyException();
        }
        this.key = new byte[DES_EDE_KEY_LEN];
        System.arraycopy(key, offset, this.key, 0, DES_EDE_KEY_LEN);
    }

    /**
     * Returns a copy of the key.
     *
     * @return a copy of the key.
     */
    public byte[] getKey() {
        byte[] result = new byte [DES_EDE_KEY_LEN];
        System.arraycopy(this.key, 0, result, 0, DES_EDE_KEY_LEN);
        return result;
    }

    /**
     * Returns whether the specified key data starting at <code>offset</code> is
     * <i>parity-adjusted</i>.
     *
     * @param key
     *            the key data.
     * @param offset
     *            the offset to start checking at.
     * @return {@code true} if the specified key data is parity-adjusted,
     *            {@code false} otherwise.
     * @throws InvalidKeyException
     *             if the length of the key data starting at offset is less than
     *             24.
     */
    public static boolean isParityAdjusted(byte[] key, int offset) throws InvalidKeyException {
        if (key.length - offset < DES_EDE_KEY_LEN) {
            throw new InvalidKeyException();
        }
        for (int i=offset; i<DES_EDE_KEY_LEN+offset; i++) {
            int b = key[i];
            if ((((b & 1) + ((b & 2) >> 1) + ((b & 4) >> 2)
                + ((b & 8) >> 3) + ((b & 16) >> 4) + ((b & 32) >> 5)
                + ((b & 64) >> 6)) & 1) == ((b & 128) >> 7)) {
                return false;
            }
        }
        return true;
    }
}