/*
 * Copyright 2010 Google Inc.
 * 
 * Licensed 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.
 */

/*
 * MODIFIED BY GOOGLE
 *
 * Originally taken from org.apache.java.security.MD5 fetched from:
 * <pre>
 * http://archive.apache.org/dist/turbine/turbine-2.1/source/turbine-src-2.1b3.tar.gz
 * </pre>
 *
 * Modified by removing test data, changing style to match GWT style guide,
 * and making it better conform to MessageDigestSpi.
 *
 * Original license below:
 */

/*
 * ==================================================================== The
 * Apache Software License, Version 1.1
 * 
 * Copyright (c) 2001 The Apache Software Foundation. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any, must
 * include the following acknowledgment: "This product includes software
 * developed by the Apache Software Foundation (http://www.apache.org/)."
 * Alternately, this acknowledgment may appear in the software itself, if and
 * wherever such third-party acknowledgments normally appear.
 * 
 * 4. The names "Apache" and "Apache Software Foundation" and "Apache Turbine"
 * must not be used to endorse or promote products derived from this software
 * without prior written permission. For written permission, please contact
 * apache@apache.org.
 * 
 * 5. Products derived from this software may not be called "Apache",
 * "Apache Turbine", nor may "Apache" appear in their name, without prior
 * written permission of the Apache Software Foundation.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE APACHE
 * SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many individuals on
 * behalf of the Apache Software Foundation. For more information on the Apache
 * Software Foundation, please see <http://www.apache.org/>.
 */
/*
 * This class implements the Message Digest 5 algorithm (MD5) as defined in
 * <a href="http://tools.ietf.org/html/rfc1321">RFC-1321</a>.
 * 
 * <p><b>Note:</b> even if standard Java 1.1 APIs already provide a MD5
 * implementation, this class is used on those Java runtime environments (like
 * Kaffe) where the package <code>java.security</code> is highly improbable to
 * be found.
 * 
 * author <a href="mailto:stefano@apache.org">Stefano Mazzocchi</a>
 */
package com.google.gwt.core.client.impl;

import java.security.MessageDigest;

/**
 * GWT implementation of MD5.
 */
public final class Md5Digest extends MessageDigest {

  // 16 * 4 bytes
  static byte padding[] = {
      (byte) 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

  /**
   * Converts a long to a 8-byte array using low order first.
   * 
   * @param n A long.
   * @return A byte[].
   */
  public static byte[] toBytes(long n) {
    byte[] b = new byte[8];

    b[0] = (byte) (n);
    n >>>= 8;
    b[1] = (byte) (n);
    n >>>= 8;
    b[2] = (byte) (n);
    n >>>= 8;
    b[3] = (byte) (n);
    n >>>= 8;
    b[4] = (byte) (n);
    n >>>= 8;
    b[5] = (byte) (n);
    n >>>= 8;
    b[6] = (byte) (n);
    n >>>= 8;
    b[7] = (byte) (n);

    return b;
  }

  /**
   * Converts a 64-byte array into a 16-int array.
   * 
   * @param in A byte[].
   * @param out An int[].
   */
  private static void byte2int(byte[] in, int[] out) {
    for (int inpos = 0, outpos = 0; outpos < 16; outpos++) {
      out[outpos] = ((in[inpos++] & 0xff) | ((in[inpos++] & 0xff) << 8)
          | ((in[inpos++] & 0xff) << 16) | ((in[inpos++] & 0xff) << 24));
    }
  }

  /*
   * Method F.
   * 
   * @param x An int.
   * @param y An int.
   * @param z An int.
   * @return An int.
   */
  private static int f(int x, int y, int z) {
    return (z ^ (x & (y ^ z)));
  }

  /*
   * Method FF.
   * 
   * @param a An int.
   * @param b An int.
   * @param c An int.
   * @param d An int.
   * @param x An int.
   * @param s An int.
   * @param ac An int.
   * @return An int.
   */
  private static int ff(int a, int b, int c, int d, int x, int s, int ac) {
    a += x + ac + f(b, c, d);
    a = (a << s | a >>> -s);
    return a + b;
  }

  /*
   * Method G.
   * 
   * @param x An int.
   * @param y An int.
   * @param z An int.
   * @return An int.
   */
  private static int g(int x, int y, int z) {
    return (y ^ (z & (x ^ y)));
  }

  /*
   * Method GG.
   * 
   * @param a An int.
   * @param b An int.
   * @param c An int.
   * @param d An int.
   * @param x An int.
   * @param s An int.
   * @param ac An int.
   * @return An int.
   */
  private static int gg(int a, int b, int c, int d, int x, int s, int ac) {
    a += x + ac + g(b, c, d);
    a = (a << s | a >>> -s);
    return a + b;
  }

  /*
   * Method H.
   * 
   * @param x An int.
   * @param y An int.
   * @param z An int.
   * @return An int.
   */
  private static int h(int x, int y, int z) {
    return (x ^ y ^ z);
  }

  /*
   * Method HH.
   * 
   * @param a An int.
   * @param b An int.
   * @param c An int.
   * @param d An int.
   * @param x An int.
   * @param s An int.
   * @param ac An int.
   * @return An int.
   */
  private static int hh(int a, int b, int c, int d, int x, int s, int ac) {
    a += x + ac + h(b, c, d);
    a = (a << s | a >>> -s);
    return a + b;
  }

  /*
   * Method I.
   * 
   * @param x An int.
   * @param y An int.
   * @param z An int.
   * @return An int.
   */
  private static int i(int x, int y, int z) {
    return (y ^ (x | ~z));
  }

  /*
   * Method II.
   * 
   * @param a An int.
   * @param b An int.
   * @param c An int.
   * @param d An int.
   * @param x An int.
   * @param s An int.
   * @param ac An int.
   * @return An int.
   */
  private static int ii(int a, int b, int c, int d, int x, int s, int ac) {
    a += x + ac + i(b, c, d);
    a = (a << s | a >>> -s);
    return a + b;
  }

  /**
   * Converts a 4-int array into a 16-byte array.
   * 
   * @param in An int[].
   * @param out A byte[].
   */
  private static void int2byte(int[] in, byte[] out) {
    for (int inpos = 0, outpos = 0; inpos < 4; inpos++) {
      out[outpos++] = (byte) (in[inpos] & 0xff);
      out[outpos++] = (byte) ((in[inpos] >>> 8) & 0xff);
      out[outpos++] = (byte) ((in[inpos] >>> 16) & 0xff);
      out[outpos++] = (byte) ((in[inpos] >>> 24) & 0xff);
    }
  }

  private byte buffer[];

  // TODO(jat): consider doing away with long math
  private long counter;

  private final byte[] oneByte = new byte[1];

  private int remainder;

  private int state[];

  private int x[];

  public Md5Digest() {
    super("MD5");
    engineReset();
  }

  @Override
  protected byte[] engineDigest() {
    byte[] bits = toBytes(counter << 3);
    byte[] digest = new byte[16];

    if (remainder > 8) {
      engineUpdate(padding, 0, remainder - 8);
    } else {
      engineUpdate(padding, 0, 64 + (remainder - 8));
    }

    engineUpdate(bits, 0, 8);

    int2byte(state, digest);

    this.reset();
    return digest;
  }

  @Override
  protected int engineGetDigestLength() {
    return 16;
  }

  @Override
  protected void engineReset() {
    buffer = new byte[64];
    state = new int[4];
    x = new int[16];

    state[0] = 0x67452301;
    state[1] = 0xefcdab89;
    state[2] = 0x98badcfe;
    state[3] = 0x10325476;

    counter = 0;
    remainder = 64;
  }

  @Override
  protected void engineUpdate(byte input) {
    // TODO(jat): better implementation
    oneByte [0] = input;
    engineUpdate(oneByte, 0, 1);
  }

  @Override
  protected void engineUpdate(byte[] input, int offset, int len) {
    while (true) {
      if (len >= remainder) {
        System.arraycopy(input, offset, buffer, (int) (counter & 63L),
            remainder);
        transform(buffer);
        counter += remainder;
        offset += remainder;
        len -= remainder;
        remainder = 64;
      } else {
        System.arraycopy(input, offset, buffer, (int) (counter & 63L), len);
        counter += len;
        remainder -= len;
        break;
      }
    }
  }

  /*
   * TODO: Document.
   * 
   * @param buffer A byte[].
   */
  private void transform(byte[] buffer) {
    int a, b, c, d;

    byte2int(buffer, x);

    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];

    a = ff(a, b, c, d, x[0], 7, 0xd76aa478);
    d = ff(d, a, b, c, x[1], 12, 0xe8c7b756);
    c = ff(c, d, a, b, x[2], 17, 0x242070db);
    b = ff(b, c, d, a, x[3], 22, 0xc1bdceee);
    a = ff(a, b, c, d, x[4], 7, 0xf57c0faf);
    d = ff(d, a, b, c, x[5], 12, 0x4787c62a);
    c = ff(c, d, a, b, x[6], 17, 0xa8304613);
    b = ff(b, c, d, a, x[7], 22, 0xfd469501);
    a = ff(a, b, c, d, x[8], 7, 0x698098d8);
    d = ff(d, a, b, c, x[9], 12, 0x8b44f7af);
    c = ff(c, d, a, b, x[10], 17, 0xffff5bb1);
    b = ff(b, c, d, a, x[11], 22, 0x895cd7be);
    a = ff(a, b, c, d, x[12], 7, 0x6b901122);
    d = ff(d, a, b, c, x[13], 12, 0xfd987193);
    c = ff(c, d, a, b, x[14], 17, 0xa679438e);
    b = ff(b, c, d, a, x[15], 22, 0x49b40821);

    a = gg(a, b, c, d, x[1], 5, 0xf61e2562);
    d = gg(d, a, b, c, x[6], 9, 0xc040b340);
    c = gg(c, d, a, b, x[11], 14, 0x265e5a51);
    b = gg(b, c, d, a, x[0], 20, 0xe9b6c7aa);
    a = gg(a, b, c, d, x[5], 5, 0xd62f105d);
    d = gg(d, a, b, c, x[10], 9, 0x2441453);
    c = gg(c, d, a, b, x[15], 14, 0xd8a1e681);
    b = gg(b, c, d, a, x[4], 20, 0xe7d3fbc8);
    a = gg(a, b, c, d, x[9], 5, 0x21e1cde6);
    d = gg(d, a, b, c, x[14], 9, 0xc33707d6);
    c = gg(c, d, a, b, x[3], 14, 0xf4d50d87);
    b = gg(b, c, d, a, x[8], 20, 0x455a14ed);
    a = gg(a, b, c, d, x[13], 5, 0xa9e3e905);
    d = gg(d, a, b, c, x[2], 9, 0xfcefa3f8);
    c = gg(c, d, a, b, x[7], 14, 0x676f02d9);
    b = gg(b, c, d, a, x[12], 20, 0x8d2a4c8a);

    a = hh(a, b, c, d, x[5], 4, 0xfffa3942);
    d = hh(d, a, b, c, x[8], 11, 0x8771f681);
    c = hh(c, d, a, b, x[11], 16, 0x6d9d6122);
    b = hh(b, c, d, a, x[14], 23, 0xfde5380c);
    a = hh(a, b, c, d, x[1], 4, 0xa4beea44);
    d = hh(d, a, b, c, x[4], 11, 0x4bdecfa9);
    c = hh(c, d, a, b, x[7], 16, 0xf6bb4b60);
    b = hh(b, c, d, a, x[10], 23, 0xbebfbc70);
    a = hh(a, b, c, d, x[13], 4, 0x289b7ec6);
    d = hh(d, a, b, c, x[0], 11, 0xeaa127fa);
    c = hh(c, d, a, b, x[3], 16, 0xd4ef3085);
    b = hh(b, c, d, a, x[6], 23, 0x4881d05);
    a = hh(a, b, c, d, x[9], 4, 0xd9d4d039);
    d = hh(d, a, b, c, x[12], 11, 0xe6db99e5);
    c = hh(c, d, a, b, x[15], 16, 0x1fa27cf8);
    b = hh(b, c, d, a, x[2], 23, 0xc4ac5665);

    a = ii(a, b, c, d, x[0], 6, 0xf4292244);
    d = ii(d, a, b, c, x[7], 10, 0x432aff97);
    c = ii(c, d, a, b, x[14], 15, 0xab9423a7);
    b = ii(b, c, d, a, x[5], 21, 0xfc93a039);
    a = ii(a, b, c, d, x[12], 6, 0x655b59c3);
    d = ii(d, a, b, c, x[3], 10, 0x8f0ccc92);
    c = ii(c, d, a, b, x[10], 15, 0xffeff47d);
    b = ii(b, c, d, a, x[1], 21, 0x85845dd1);
    a = ii(a, b, c, d, x[8], 6, 0x6fa87e4f);
    d = ii(d, a, b, c, x[15], 10, 0xfe2ce6e0);
    c = ii(c, d, a, b, x[6], 15, 0xa3014314);
    b = ii(b, c, d, a, x[13], 21, 0x4e0811a1);
    a = ii(a, b, c, d, x[4], 6, 0xf7537e82);
    d = ii(d, a, b, c, x[11], 10, 0xbd3af235);
    c = ii(c, d, a, b, x[2], 15, 0x2ad7d2bb);
    b = ii(b, c, d, a, x[9], 21, 0xeb86d391);

    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
  }
}