/*
 * @(#)MD5.java	1.8 95/04/02  
 *
 * Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

package java.security;

import java.util.*;
import java.lang.*;


/**
 * The MD5 class is used to compute an MD5 message digest over a given
 * buffer of bytes. It is an implementation of the RSA Data Security Inc
 * MD5 algorithim as described in internet RFC 1321.
 * @version 	02 Apr 1995, 1.8
 * @author 	Chuck McManis
 */
public final class MD5 extends MessageDigest {
    /** containss the computed message digest */

    private int state[];
    private long count;
    private byte buffer[];
    private static int transformBuffer[];

    private static final int S11 = 7;
    private static final int S12 = 12;
    private static final int S13 = 17;
    private static final int S14 = 22;
    private static final int S21 = 5;
    private static final int S22 = 9;
    private static final int S23 = 14;
    private static final int S24 = 20;
    private static final int S31 = 4;
    private static final int S32 = 11;
    private static final int S33 = 16;
    private static final int S34 = 23;
    private static final int S41 = 6;
    private static final int S42 = 10;
    private static final int S43 = 15;
    private static final int S44 = 21;

    /**
     * Standard constructor, creates a new MD5 instance, allocates its
     * buffers from the heap.
     */
    public MD5() {
	state = new int[4];
	count = 0;
	if (transformBuffer == null)
	    transformBuffer = new int[16];
	buffer = new byte[64];
	digestBits = new byte[16];
	digestValid = false;
    }

    /**
     * Alternate constructor, allows you to pass in the buffer where you
     * want the resulting digest stored.
     */
    public MD5(byte mydigest[]) {
	state = new int[4];
	count = 0;
	if (transformBuffer == null)
	    transformBuffer = new int[16];
	buffer = new byte[64];
	digestBits = mydigest;
	digestValid = false;
    }

    /* **********************************************************
     * The MD5 Functions. These are copied verbatim from
     * the RFC to insure accuracy. The results of this
     * implementation were checked against the RSADSI version.
     * **********************************************************
     */

    private int F(int x, int y, int z) {
	return ((x & y) | ((~x) & z));
    }

    private int G(int x, int y, int z) {
	return ((x & z) | (y & (~z)));
    }

    private int H(int x, int y, int z) {
	return ((x ^ y) ^ z);
    }

    private int I(int x, int y, int z) {
	return (y ^ (x | (~z)));
    }

    private int rotateLeft(int a, int n) {
	return ((a << n) | (a >>> (32 - n)));
    }

    private int FF(int a, int b, int c, int d, int x, int s, int ac) {
	a += F(b, c, d) + x + ac;
	a = rotateLeft(a, s);
	a += b;
	return a;
    }

    private int GG(int a, int b, int c, int d, int x, int s, int ac) {
	a += G(b, c, d) + x + ac;
	a = rotateLeft(a, s);
	a += b;
	return a;
    }

    private int HH(int a, int b, int c, int d, int x, int s, int ac) {
	a += H(b, c, d) + x + ac;
	a = rotateLeft(a, s);
	a += b;
	return a;
    }

    private int II(int a, int b, int c, int d, int x, int s, int ac) {
	a += I(b, c, d) + x + ac;
	a = rotateLeft(a, s);
	a += b;
	return a;
    }

    /**
     * This is where the functions come together as the generic MD5
     * transformation operation, it is called by update() which is
     * synchronized (to protect transformBuffer)
     */
    void transform(byte buf[], int offset) {
	int a, b, c, d;
	int x[] = transformBuffer;
	
	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];
	
	for (int i = 0; i < 16; i++) {
	    x[i] = (int)buf[i*4+offset] & 0xff;
	    for (int j = 1; j < 4; j++) {
		x[i] += ((int)buf[i*4+j+offset] & 0xff) << (j * 8);
	    }
	}

	/* Round 1 */
	a = FF ( a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
	d = FF ( d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
	c = FF ( c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
	b = FF ( b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
	a = FF ( a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
	d = FF ( d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
	c = FF ( c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
	b = FF ( b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
	a = FF ( a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
	d = FF ( d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
	c = FF ( c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
	b = FF ( b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
	a = FF ( a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
	d = FF ( d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
	c = FF ( c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
	b = FF ( b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

	/* Round 2 */
	a = GG ( a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
	d = GG ( d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
	c = GG ( c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
	b = GG ( b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
	a = GG ( a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
	d = GG ( d, a, b, c, x[10], S22,  0x2441453); /* 22 */
	c = GG ( c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
	b = GG ( b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
	a = GG ( a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
	d = GG ( d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
	c = GG ( c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
	b = GG ( b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
	a = GG ( a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
	d = GG ( d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
	c = GG ( c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
	b = GG ( b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

	/* Round 3 */
	a = HH ( a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
	d = HH ( d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
	c = HH ( c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
	b = HH ( b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
	a = HH ( a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
	d = HH ( d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
	c = HH ( c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
	b = HH ( b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
	a = HH ( a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
	d = HH ( d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
	c = HH ( c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
	b = HH ( b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
	a = HH ( a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
	d = HH ( d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
	c = HH ( c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
	b = HH ( b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

	/* Round 4 */
	a = II ( a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
	d = II ( d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
	c = II ( c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
	b = II ( b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
	a = II ( a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
	d = II ( d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
	c = II ( c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
	b = II ( b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
	a = II ( a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
	d = II ( d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
	c = II ( c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
	b = II ( b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
	a = II ( a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
	d = II ( d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
	c = II ( c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
	b = II ( b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

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

    /**
     * Initialize the MD5 state information and reset the bit count
     * to 0. Given this implementation you are constrained to counting
     * 2^64 bits.
     */
    public void init() {
	count = 0;
 	// Load magic initialization constants.
	state[0] = 0x67452301;
	state[1] = 0xefcdab89;
	state[2] = 0x98badcfe;
	state[3] = 0x10325476;
	digestValid = false;
	for (int i = 0; i < digestBits.length; i++)
	    digestBits[i] = 0;
    }

    /**
     * update adds the passed type to the input buffer
     */
    public synchronized void update(byte b) {
	int	index;
	
	index = (int) ((count >>> 3) & 0x3f);
	count += 8;
	buffer[index] = b;
	if (index  >= 63) {
	    transform(buffer, 0);
	}
    }

    /**
     * Perform the final computations, any buffered bytes are added
     * to the digest, the count is added to the digest, and the resulting
     * digest is stored. After calling final you will need to call
     * init() again to do another digest.
     */
    public void finish() {
	byte	bits[] = new byte[8];
	byte	padding[];
	int	i, index, padLen;

	for (i = 0; i < 8; i++) {
	    bits[i] = (byte)((count >>> (i * 8)) & 0xff);
	}
	
	index = (int)(count >> 3) & 0x3f;
	padLen = (index < 56) ? (56 - index) : (120 - index);
	padding = new byte[padLen];
	padding[0] = (byte) 0x80;
	update(padding);
	update(bits);
	
	for (i = 0; i < 4; i++) {
	    for (int j = 0; j < 4; j++) {
		digestBits[i*4+j] = (byte)((state[i] >>> (j * 8)) & 0xff);
	    }
	}
	digestValid = true;
    }

}