/*

 * Copyright (c) 2010, Isode Limited, London, England.

 * All rights reserved.

 */

/*

 * Copyright (c) 2010, Remko Tronçon.

 * All rights reserved.

 */

package com.isode.stroke.stringcodecs;

import com.isode.stroke.base.ByteArray;

public class HMACSHA1 {

    private static final int B = 64;

    public static ByteArray getResult(ByteArray key, ByteArray data) {

        assert key.getSize() <= B;

        /* And an assert that does something */

        if (key.getSize() > B) {

            throw new IllegalStateException("Invalid key size.");

        }

        // Create the padded key

        ByteArray paddedKey = new ByteArray(key);

        for (int i = key.getSize(); i < B; ++i) {

            paddedKey.append((byte) 0x0);

        }

        // Create the first value

        ByteArray x = new ByteArray(paddedKey);

        byte[] xInner = x.getData();

        for (int i = 0; i < xInner.length; ++i) {

            xInner[i] ^= 0x36;

        }

        x.append(data);

        // Create the second value

        ByteArray y = new ByteArray(paddedKey);

        byte[] yInner = y.getData();

        for (int i = 0; i < yInner.length; ++i) {

            yInner[i] ^= 0x5c;

        }

        y.append(SHA1.getHash(x));

        return SHA1.getHash(y);

    }

}