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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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 org.jboss.netty.handler.codec.http.websocketx;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.handler.codec.base64.Base64;
import org.jboss.netty.util.CharsetUtil;

/**
 * TODO Document me.
 */
final class WebSocketUtil {

    /**
     * Performs an MD5 hash
     *
     * @param buffer
     *            buffer to hash
     * @return Hashed data
     */
    static ChannelBuffer md5(ChannelBuffer buffer) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            if (buffer.hasArray()) {
                int offset = buffer.arrayOffset() + buffer.readerIndex();
                int length = buffer.readableBytes();
                md.update(buffer.array(), offset, length);
            } else {
                md.update(buffer.toByteBuffer());
            }
            return ChannelBuffers.wrappedBuffer(md.digest());
        } catch (NoSuchAlgorithmException e) {
            throw new InternalError("MD5 not supported on this platform");
        }
    }

    /**
     * Performs an SHA-1 hash
     *
     * @param buffer
     *            buffer to hash
     * @return Hashed data
     */
    static ChannelBuffer sha1(ChannelBuffer buffer) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA1");
            if (buffer.hasArray()) {
                int offset = buffer.arrayOffset() + buffer.readerIndex();
                int length = buffer.readableBytes();
                md.update(buffer.array(), offset, length);
            } else {
                md.update(buffer.toByteBuffer());
            }
            return ChannelBuffers.wrappedBuffer(md.digest());
        } catch (NoSuchAlgorithmException e) {
            throw new InternalError("SHA-1 not supported on this platform");
        }
    }

    /**
     * Base 64 encoding
     *
     * @param buffer
     *            Bytes to encode
     * @return encoded string
     */
    static String base64(ChannelBuffer buffer) {
        return Base64.encode(buffer).toString(CharsetUtil.UTF_8);
    }

    /**
     * Creates some random bytes
     *
     * @param size
     *            Number of random bytes to create
     * @return random bytes
     */
    static byte[] randomBytes(int size) {
        byte[] bytes = new byte[size];

        for (int i = 0; i < size; i++) {
            bytes[i] = (byte) randomNumber(0, 255);
        }

        return bytes;
    }

    /**
     * Generates a random number
     *
     * @param min
     *            Minimum value
     * @param max
     *            Maximum value
     * @return Random number
     */
    static int randomNumber(int min, int max) {
        return (int) (Math.random() * max + min);
    }

    private WebSocketUtil() {
        // Unused
    }
}