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/*
 * Copyright (c) 2011, 2020 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.glassfish.grizzly.websockets;

import java.security.SecureRandom;

import org.glassfish.grizzly.Buffer;

public class Masker {
    private Buffer buffer;
    private byte[] mask;
    private int index = 0;

    public Masker(Buffer buffer) {
        this.buffer = buffer;
    }

    public Masker() {
        generateMask();
    }

    public byte get() {
        return buffer.get();
    }

    public byte[] get(final int size) {
        byte[] bytes = new byte[size];
        buffer.get(bytes);
        return bytes;
    }

    public byte unmask() {
        final byte b = get();
        return mask == null ? b : (byte) (b ^ mask[index++ % Constants.MASK_SIZE]);
    }

    public byte[] unmask(int count) {
        byte[] bytes = get(count);
        if (mask != null) {
            for (int i = 0; i < bytes.length; i++) {
                bytes[i] ^= mask[index++ % Constants.MASK_SIZE];
            }
        }

        return bytes;
    }

    public void generateMask() {
        mask = new byte[Constants.MASK_SIZE];
        new SecureRandom().nextBytes(mask);
    }

    public void mask(byte[] bytes, int location, byte b) {
        bytes[location] = mask == null ? b : (byte) (b ^ mask[index++ % Constants.MASK_SIZE]);
    }

    public void mask(byte[] target, int location, byte[] bytes) {
        if (bytes != null && target != null) {
            for (int i = 0; i < bytes.length; i++) {
                target[location + i] = mask == null ? bytes[i] : (byte) (bytes[i] ^ mask[index++ % Constants.MASK_SIZE]);
            }
        }
    }

    public byte[] maskAndPrepend(byte[] packet) {
        byte[] masked = new byte[packet.length + Constants.MASK_SIZE];
        System.arraycopy(getMask(), 0, masked, 0, Constants.MASK_SIZE);
        mask(masked, Constants.MASK_SIZE, packet);
        return masked;
    }

    public void setBuffer(Buffer buffer) {
        this.buffer = buffer;
    }

    public byte[] getMask() {
        return mask;
    }

    public void readMask() {
        mask = get(Constants.MASK_SIZE);
    }
}