/*
 * Copyright (c) 2000-2021 The Legion of the Bouncy Castle Inc. (https://www.bouncycastle.org)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
 * and associated documentation files (the "Software"), to deal in the Software without restriction, 
 * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 * 
 */

package net.lax1dude.eaglercraft.v1_8.crypto;

/**
 * implementation of MD5 as outlined in "Handbook of Applied Cryptography",
 * pages 346 - 347.
 */
public class MD5Digest extends GeneralDigest {
	private static final int DIGEST_LENGTH = 16;

	private int H1, H2, H3, H4; // IV's

	private int[] X = new int[16];
	private int xOff;

	/**
	 * Standard constructor
	 */
	public MD5Digest() {
		reset();
	}

	public String getAlgorithmName() {
		return "MD5";
	}

	public int getDigestSize() {
		return DIGEST_LENGTH;
	}

	protected void processWord(byte[] in, int inOff) {
		X[xOff++] = (in[inOff] & 0xff) | ((in[inOff + 1] & 0xff) << 8) | ((in[inOff + 2] & 0xff) << 16)
				| ((in[inOff + 3] & 0xff) << 24);

		if (xOff == 16) {
			processBlock();
		}
	}

	protected void processLength(long bitLength) {
		if (xOff > 14) {
			processBlock();
		}

		X[14] = (int) (bitLength & 0xffffffff);
		X[15] = (int) (bitLength >>> 32);
	}

	private void unpackWord(int word, byte[] out, int outOff) {
		out[outOff] = (byte) word;
		out[outOff + 1] = (byte) (word >>> 8);
		out[outOff + 2] = (byte) (word >>> 16);
		out[outOff + 3] = (byte) (word >>> 24);
	}

	public int doFinal(byte[] out, int outOff) {
		finish();

		unpackWord(H1, out, outOff);
		unpackWord(H2, out, outOff + 4);
		unpackWord(H3, out, outOff + 8);
		unpackWord(H4, out, outOff + 12);

		reset();

		return DIGEST_LENGTH;
	}

	/**
	 * reset the chaining variables to the IV values.
	 */
	public void reset() {
		super.reset();

		H1 = 0x67452301;
		H2 = 0xefcdab89;
		H3 = 0x98badcfe;
		H4 = 0x10325476;

		xOff = 0;

		for (int i = 0; i != X.length; i++) {
			X[i] = 0;
		}
	}

	//
	// round 1 left rotates
	//
	private static final int S11 = 7;
	private static final int S12 = 12;
	private static final int S13 = 17;
	private static final int S14 = 22;

	//
	// round 2 left rotates
	//
	private static final int S21 = 5;
	private static final int S22 = 9;
	private static final int S23 = 14;
	private static final int S24 = 20;

	//
	// round 3 left rotates
	//
	private static final int S31 = 4;
	private static final int S32 = 11;
	private static final int S33 = 16;
	private static final int S34 = 23;

	//
	// round 4 left rotates
	//
	private static final int S41 = 6;
	private static final int S42 = 10;
	private static final int S43 = 15;
	private static final int S44 = 21;

	/*
	 * rotate int x left n bits.
	 */
	private int rotateLeft(int x, int n) {
		return (x << n) | (x >>> (32 - n));
	}

	/*
	 * F, G, H and I are the basic MD5 functions.
	 */
	private int F(int u, int v, int w) {
		return (u & v) | (~u & w);
	}

	private int G(int u, int v, int w) {
		return (u & w) | (v & ~w);
	}

	private int H(int u, int v, int w) {
		return u ^ v ^ w;
	}

	private int K(int u, int v, int w) {
		return v ^ (u | ~w);
	}

	protected void processBlock() {
		int a = H1;
		int b = H2;
		int c = H3;
		int d = H4;

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

		//
		// Round 2 - G cycle, 16 times.
		//
		a = rotateLeft(a + G(b, c, d) + X[1] + 0xf61e2562, S21) + b;
		d = rotateLeft(d + G(a, b, c) + X[6] + 0xc040b340, S22) + a;
		c = rotateLeft(c + G(d, a, b) + X[11] + 0x265e5a51, S23) + d;
		b = rotateLeft(b + G(c, d, a) + X[0] + 0xe9b6c7aa, S24) + c;
		a = rotateLeft(a + G(b, c, d) + X[5] + 0xd62f105d, S21) + b;
		d = rotateLeft(d + G(a, b, c) + X[10] + 0x02441453, S22) + a;
		c = rotateLeft(c + G(d, a, b) + X[15] + 0xd8a1e681, S23) + d;
		b = rotateLeft(b + G(c, d, a) + X[4] + 0xe7d3fbc8, S24) + c;
		a = rotateLeft(a + G(b, c, d) + X[9] + 0x21e1cde6, S21) + b;
		d = rotateLeft(d + G(a, b, c) + X[14] + 0xc33707d6, S22) + a;
		c = rotateLeft(c + G(d, a, b) + X[3] + 0xf4d50d87, S23) + d;
		b = rotateLeft(b + G(c, d, a) + X[8] + 0x455a14ed, S24) + c;
		a = rotateLeft(a + G(b, c, d) + X[13] + 0xa9e3e905, S21) + b;
		d = rotateLeft(d + G(a, b, c) + X[2] + 0xfcefa3f8, S22) + a;
		c = rotateLeft(c + G(d, a, b) + X[7] + 0x676f02d9, S23) + d;
		b = rotateLeft(b + G(c, d, a) + X[12] + 0x8d2a4c8a, S24) + c;

		//
		// Round 3 - H cycle, 16 times.
		//
		a = rotateLeft(a + H(b, c, d) + X[5] + 0xfffa3942, S31) + b;
		d = rotateLeft(d + H(a, b, c) + X[8] + 0x8771f681, S32) + a;
		c = rotateLeft(c + H(d, a, b) + X[11] + 0x6d9d6122, S33) + d;
		b = rotateLeft(b + H(c, d, a) + X[14] + 0xfde5380c, S34) + c;
		a = rotateLeft(a + H(b, c, d) + X[1] + 0xa4beea44, S31) + b;
		d = rotateLeft(d + H(a, b, c) + X[4] + 0x4bdecfa9, S32) + a;
		c = rotateLeft(c + H(d, a, b) + X[7] + 0xf6bb4b60, S33) + d;
		b = rotateLeft(b + H(c, d, a) + X[10] + 0xbebfbc70, S34) + c;
		a = rotateLeft(a + H(b, c, d) + X[13] + 0x289b7ec6, S31) + b;
		d = rotateLeft(d + H(a, b, c) + X[0] + 0xeaa127fa, S32) + a;
		c = rotateLeft(c + H(d, a, b) + X[3] + 0xd4ef3085, S33) + d;
		b = rotateLeft(b + H(c, d, a) + X[6] + 0x04881d05, S34) + c;
		a = rotateLeft(a + H(b, c, d) + X[9] + 0xd9d4d039, S31) + b;
		d = rotateLeft(d + H(a, b, c) + X[12] + 0xe6db99e5, S32) + a;
		c = rotateLeft(c + H(d, a, b) + X[15] + 0x1fa27cf8, S33) + d;
		b = rotateLeft(b + H(c, d, a) + X[2] + 0xc4ac5665, S34) + c;

		//
		// Round 4 - K cycle, 16 times.
		//
		a = rotateLeft(a + K(b, c, d) + X[0] + 0xf4292244, S41) + b;
		d = rotateLeft(d + K(a, b, c) + X[7] + 0x432aff97, S42) + a;
		c = rotateLeft(c + K(d, a, b) + X[14] + 0xab9423a7, S43) + d;
		b = rotateLeft(b + K(c, d, a) + X[5] + 0xfc93a039, S44) + c;
		a = rotateLeft(a + K(b, c, d) + X[12] + 0x655b59c3, S41) + b;
		d = rotateLeft(d + K(a, b, c) + X[3] + 0x8f0ccc92, S42) + a;
		c = rotateLeft(c + K(d, a, b) + X[10] + 0xffeff47d, S43) + d;
		b = rotateLeft(b + K(c, d, a) + X[1] + 0x85845dd1, S44) + c;
		a = rotateLeft(a + K(b, c, d) + X[8] + 0x6fa87e4f, S41) + b;
		d = rotateLeft(d + K(a, b, c) + X[15] + 0xfe2ce6e0, S42) + a;
		c = rotateLeft(c + K(d, a, b) + X[6] + 0xa3014314, S43) + d;
		b = rotateLeft(b + K(c, d, a) + X[13] + 0x4e0811a1, S44) + c;
		a = rotateLeft(a + K(b, c, d) + X[4] + 0xf7537e82, S41) + b;
		d = rotateLeft(d + K(a, b, c) + X[11] + 0xbd3af235, S42) + a;
		c = rotateLeft(c + K(d, a, b) + X[2] + 0x2ad7d2bb, S43) + d;
		b = rotateLeft(b + K(c, d, a) + X[9] + 0xeb86d391, S44) + c;

		H1 += a;
		H2 += b;
		H3 += c;
		H4 += d;

		//
		// reset the offset and clean out the word buffer.
		//
		xOff = 0;
		for (int i = 0; i != X.length; i++) {
			X[i] = 0;
		}
	}

}
