package cn.edu.buaa.nlsde.md5;
import java.lang.reflect.*;
/*************************************************
MD5 類實現了RSA Data Security, Inc.在提交給IETF
的RFC1321中的MD5 message-digest 算法。
*************************************************/
public class MD5Algorithm1 {
	/**
	 * 下面這些S11-S44實際上是一個4*4的矩陣，
	 * 在原始的C實現中是用#define 實現的，
	 * 這里把它們實現成為static final是表示了只讀，
	 * 能在同一個進程空間內的多個Instance間共享
	 */
	static final int S11 = 7;
	static final int S12 = 12;
	static final int S13 = 17;
	static final int S14 = 22;
	static final int S21 = 5;
	static final int S22 = 9;
	static final int S23 = 14;
	static final int S24 = 20;
	static final int S31 = 4;
	static final int S32 = 11;
	static final int S33 = 16;
	static final int S34 = 23;
	static final int S41 = 6;
	static final int S42 = 10;
	static final int S43 = 15;
	static final int S44 = 21;
	static final byte[] PADDING =
		{
			-128,
			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 };
	/**
	 * 下面的三個成員是MD5計算過程中用到的3個核心數據，
	 * 在原始的C實現中被定義到MD5_CTX結構中 	
	 */
	private long[] state = new long[4]; // state (ABCD)
	private long[] count = new long[2];
	// number of bits, modulo 2^64 (lsb first)
	private byte[] buffer = new byte[64]; // input buffer
	/**
	 * digestHexStr是MD5的唯一一個公共成員，
	 * 是最新一次計算結果的16進制ASCII表示.
	 */
	public String digestHexStr;
	/**
	 *  digest,是最新一次計算結果的2進制內部表示，表示128bit的MD5值.
	 */
	private byte[] digest = new byte[16];
	/**
	 * getMD5ofStr是類MD5最主要的公共方法，
	 * 入口參數是你想要進行MD5變換的字符串返回的是變換完的結果，
	 * 這個結果是從公共成員digestHexStr取得的．
	 * @param inbuf
	 * @return
	 */
	public String getMD5ofStr(String inbuf) {
		md5Init();
		md5Update(inbuf.getBytes(), inbuf.length());
		md5Final();
		digestHexStr = "";
		for (int i = 0; i < 16; i++) {
			digestHexStr += byteHEX(digest[i]);
		}
		return digestHexStr;
	}
	/**
	 * 這是MD5這個類的標準構造函數，
	 * JavaBean要求有一個public的并且沒有參數的構造函數
	 */
	public MD5Algorithm1() {
		md5Init();
		return;
	}
	/**
	 * md5Init是一個初始化函數，初始化核心變量，裝入標準的幻數
	 */
	private void md5Init() {
		count[0] = 0L;
		count[1] = 0L;
		///* Load magic initialization constants.
		state[0] = 0x67452301L;
		state[1] = 0xefcdab89L;
		state[2] = 0x98badcfeL;
		state[3] = 0x10325476L;
		return;
	}
	/**
	 * F, G, H ,I 是4個基本的MD5函數，在原始的MD5的C實現中，
	 * 由于它們是簡單的位運算，可能出于效率的考慮把它們實現成了宏，
	 * 在java中，我們把它們實現成了private方法，名字保持了原來C中的。
	 * @param x
	 * @param y
	 * @param z
	 * @return
	 */
	private long F(long x, long y, long z) {
		return (x & y) | ((~x) & z);
	}
	private long G(long x, long y, long z) {
		return (x & z) | (y & (~z));
	}
	private long H(long x, long y, long z) {
		return x ^ y ^ z;
	}
	private long I(long x, long y, long z) {
		return y ^ (x | (~z));
	}
	/**
	 * FF,GG,HH和II將調用F,G,H,I進行近一步變換
	 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4. 
	 * Rotation is separate from addition to prevent recomputation.
	 * @param a
	 * @param b
	 * @param c
	 * @param d
	 * @param x
	 * @param s
	 * @param ac
	 * @return
	 */
	private long FF(
		long a,
		long b,
		long c,
		long d,
		long x,
		long s,
		long ac) {
		a += F(b, c, d) + x + ac;
		a = ((int)a << s) | ((int)a >>> (32 - s));
		a += b;
		return a;
	}
	private long GG(
		long a,
		long b,
		long c,
		long d,
		long x,
		long s,
		long ac) {
		a += G(b, c, d) + x + ac;
		a = ((int)a << s) | ((int)a >>> (32 - s));
		a += b;
		return a;
	}
	private long HH(
		long a,
		long b,
		long c,
		long d,
		long x,
		long s,
		long ac) {
		a += H(b, c, d) + x + ac;
		a = ((int)a << s) | ((int)a >>> (32 - s));
		a += b;
		return a;
	}
	private long II(
		long a,
		long b,
		long c,
		long d,
		long x,
		long s,
		long ac) {
		a += I(b, c, d) + x + ac;
		a = ((int)a << s) | ((int)a >>> (32 - s));
		a += b;
		return a;
	}
	/**
	 * md5Update是MD5的主計算過程，inbuf是要變換的字節串，inputlen是長度，
	 * 這個函數由getMD5ofStr調用，調用之前需要調用md5init，因此把它設計成private的
	 * @param inbuf
	 * @param inputLen
	 */
	private void md5Update(byte[] inbuf, int inputLen) {
		int i, index, partLen;
		byte[] block = new byte[64];
		index = (int) (count[0] >>> 3) & 0x3F;
		// /* Update number of bits */
		if ((count[0] += (inputLen << 3)) < (inputLen << 3))
			count[1]++;
		count[1] += (inputLen >>> 29);
		partLen = 64 - index;
		// Transform as many times as possible.
		if (inputLen >= partLen) {
			md5Memcpy(buffer, inbuf, index, 0, partLen);
			md5Transform(buffer);
			for (i = partLen; i + 63 < inputLen; i += 64) {
				md5Memcpy(block, inbuf, 0, i, 64);
				md5Transform(block);
			}
			index = 0;
		}
		else
			i = 0;
		///* Buffer remaining input */
		md5Memcpy(buffer, inbuf, index, i, inputLen - i);
	}
	/**
	 * md5Final整理和填寫輸出結果
	 */
	private void md5Final() {
		byte[] bits = new byte[8];
		int index, padLen;
		///* Save number of bits */
		Encode(bits, count, 8);
		///* Pad out to 56 mod 64.
		index = (int) (count[0] >>> 3) & 0x3f;
		padLen = (index < 56) ? (56 - index) : (120 - index);
		md5Update(PADDING, padLen);
		///* Append length (before padding) */
		md5Update(bits, 8);
		///* Store state in digest */
		Encode(digest, state, 16);
	}
	/**
	 * md5Memcpy是一個內部使用的byte數組的塊拷貝函數，
	 * 從input的inpos開始把len長度的字節拷貝到output的outpos位置開始
	 * @param output
	 * @param input
	 * @param outpos
	 * @param inpos
	 * @param len
	 */
	private void md5Memcpy(
		byte[] output,
		byte[] input,
		int outpos,
		int inpos,
		int len) {
		int i;
		for (i = 0; i < len; i++)
			output[outpos + i] = input[inpos + i];
	}
	/**
	 * md5Transform是MD5核心變換程序，有md5Update調用，block是分塊的原始字節
	 * @param block
	 */
	private void md5Transform(byte block[]) {
		long a = state[0], b = state[1], c = state[2], d = state[3];
		long[] x = new long[16];
		Decode(x, block, 64);
		/* Round 1 */
		a = FF(a, b, c, d, x[0], S11, 0xd76aa478L); /* 1 */
		d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L); /* 2 */
		c = FF(c, d, a, b, x[2], S13, 0x242070dbL); /* 3 */
		b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL); /* 4 */
		a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL); /* 5 */
		d = FF(d, a, b, c, x[5], S12, 0x4787c62aL); /* 6 */
		c = FF(c, d, a, b, x[6], S13, 0xa8304613L); /* 7 */
		b = FF(b, c, d, a, x[7], S14, 0xfd469501L); /* 8 */
		a = FF(a, b, c, d, x[8], S11, 0x698098d8L); /* 9 */
		d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL); /* 10 */
		c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L); /* 11 */
		b = FF(b, c, d, a, x[11], S14, 0x895cd7beL); /* 12 */
		a = FF(a, b, c, d, x[12], S11, 0x6b901122L); /* 13 */
		d = FF(d, a, b, c, x[13], S12, 0xfd987193L); /* 14 */
		c = FF(c, d, a, b, x[14], S13, 0xa679438eL); /* 15 */
		b = FF(b, c, d, a, x[15], S14, 0x49b40821L); /* 16 */
		/* Round 2 */
		a = GG(a, b, c, d, x[1], S21, 0xf61e2562L); /* 17 */
		d = GG(d, a, b, c, x[6], S22, 0xc040b340L); /* 18 */
		c = GG(c, d, a, b, x[11], S23, 0x265e5a51L); /* 19 */
		b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL); /* 20 */
		a = GG(a, b, c, d, x[5], S21, 0xd62f105dL); /* 21 */
		d = GG(d, a, b, c, x[10], S22, 0x2441453L); /* 22 */
		c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L); /* 23 */
		b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L); /* 24 */
		a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L); /* 25 */
		d = GG(d, a, b, c, x[14], S22, 0xc33707d6L); /* 26 */
		c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L); /* 27 */
		b = GG(b, c, d, a, x[8], S24, 0x455a14edL); /* 28 */
		a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L); /* 29 */
		d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L); /* 30 */
		c = GG(c, d, a, b, x[7], S23, 0x676f02d9L); /* 31 */
		b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL); /* 32 */
		/* Round 3 */
		a = HH(a, b, c, d, x[5], S31, 0xfffa3942L); /* 33 */
		d = HH(d, a, b, c, x[8], S32, 0x8771f681L); /* 34 */
		c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L); /* 35 */
		b = HH(b, c, d, a, x[14], S34, 0xfde5380cL); /* 36 */
		a = HH(a, b, c, d, x[1], S31, 0xa4beea44L); /* 37 */
		d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L); /* 38 */
		c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L); /* 39 */
		b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L); /* 40 */
		a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L); /* 41 */
		d = HH(d, a, b, c, x[0], S32, 0xeaa127faL); /* 42 */
		c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L); /* 43 */
		b = HH(b, c, d, a, x[6], S34, 0x4881d05L); /* 44 */
		a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L); /* 45 */
		d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L); /* 46 */
		c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L); /* 47 */
		b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L); /* 48 */
		/* Round 4 */
		a = II(a, b, c, d, x[0], S41, 0xf4292244L); /* 49 */
		d = II(d, a, b, c, x[7], S42, 0x432aff97L); /* 50 */
		c = II(c, d, a, b, x[14], S43, 0xab9423a7L); /* 51 */
		b = II(b, c, d, a, x[5], S44, 0xfc93a039L); /* 52 */
		a = II(a, b, c, d, x[12], S41, 0x655b59c3L); /* 53 */
		d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L); /* 54 */
		c = II(c, d, a, b, x[10], S43, 0xffeff47dL); /* 55 */
		b = II(b, c, d, a, x[1], S44, 0x85845dd1L); /* 56 */
		a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL); /* 57 */
		d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L); /* 58 */
		c = II(c, d, a, b, x[6], S43, 0xa3014314L); /* 59 */
		b = II(b, c, d, a, x[13], S44, 0x4e0811a1L); /* 60 */
		a = II(a, b, c, d, x[4], S41, 0xf7537e82L); /* 61 */
		d = II(d, a, b, c, x[11], S42, 0xbd3af235L); /* 62 */
		c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL); /* 63 */
		b = II(b, c, d, a, x[9], S44, 0xeb86d391L); /* 64 */
		state[0] += a;
		state[1] += b;
		state[2] += c;
		state[3] += d;
	}
	/**
	 * Encode把long數組按順序拆成byte數組，因為java的long類型是64bit的，
	 * 只拆低32bit，以適應原始C實現的用途
	 * @param output
	 * @param input
	 * @param len
	 */
	private void Encode(byte[] output, long[] input, int len) {
		int i, j;
		for (i = 0, j = 0; j < len; i++, j += 4) {
			output[j] = (byte) (input[i] & 0xffL);
			output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);
			output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);
			output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);
		}
	}
	/**
	 * Decode把byte數組按順序合成成long數組，因為java的long類型是64bit的，
	 * 只合成低32bit，高32bit清零，以適應原始C實現的用途
	 * @param output
	 * @param input
	 * @param len
	 */
	private void Decode(long[] output, byte[] input, int len) {
		int i, j;
		for (i = 0, j = 0; j < len; i++, j += 4)
			output[i] =
				b2iu(input[j])
					| (b2iu(input[j + 1]) << 8)
					| (b2iu(input[j + 2]) << 16)
					| (b2iu(input[j + 3]) << 24);
		return;
	}
	/**
	 * b2iu是一個把byte按照不考慮正負號的原則的＂升位＂程序，
	 * 因為java沒有unsigned運算
	 * @param b
	 * @return
	 */
	public static long b2iu(byte b) {
		return b < 0 ? b & 0x7F + 128 : b;
	}
	/**
	 * byteHEX()，用來把一個byte類型的數轉換成十六進制的ASCII表示，
	 * 因為java中的byte的toString無法實現這一點，
	 * 我們又沒有C語言中的sprintf(outbuf,"%02X",ib)
	 * @param ib
	 * @return
	 */
	public static String byteHEX(byte ib) {
		char[] Digit =
			{
				'0',
				'1',
				'2',
				'3',
				'4',
				'5',
				'6',
				'7',
				'8',
				'9',
				'A',
				'B',
				'C',
				'D',
				'E',
				'F' };
		char[] ob = new char[2];
		ob[0] = Digit[(ib >>> 4) & 0X0F];
		ob[1] = Digit[ib & 0X0F];
		String s = new String(ob);
		return s;
	}
	public String toMD5(String source) {
		return this.getMD5ofStr(source);
	}
	public static void main(String args[]) {
		MD5Algorithm1 m = new MD5Algorithm1();
		if (Array.getLength(args) == 0) { //如果沒有參數，執行標準的Test Suite
			System.out.println("MD5 Test suite:");
			System.out.println("MD5(\"\"):" + m.getMD5ofStr(""));
			System.out.println("MD5(\"a\"):" + m.getMD5ofStr("a"));
			System.out.println(
				"MD5(\"\"):" + m.getMD5ofStr("").length());
			System.out.println(
				"MD5(\"a\"):" + m.getMD5ofStr("a").length());
			System.out.println(
				"MD5(\"abc\"):" + m.getMD5ofStr("abc"));
			System.out.println(
				"MD5(\"message digest\"):"
					+ m.getMD5ofStr("message digest"));
			System.out.println(
				"MD5(\"abcdefghijklmnopqrstuvwxyz\"):"
					+ m.getMD5ofStr("abcdefghijklmnopqrstuvwxyz"));
			System.out.println(
				"MD5(\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\"):"
					+ m.getMD5ofStr(
						"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"));
		}
		else
			System.out.println(
				"MD5(" + args[0] + ")=" + m.getMD5ofStr(args[0]));
	}
}