BaseOkHttp/okhttplib/src/main/java/com/benyanyi/okhttp/Md5keyUtil.java

package com.benyanyi.okhttp;

/**
 * @author myLove
 */

class Md5keyUtil {
    /**
     * 下面这些S11-S44实际上是一个4*4的矩阵，在原始的C实现中是用#define 实现的， 这里把它们实现成为static final是表示了只读，切能在同一个进程空间内的多个 Instance间共享
     */
    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;

    private 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};

    /**
     * 下面的三个成员是keyBean计算过程中用到的3个核心数据，在原始的C实现中 被定义到keyBean_CTX结构中
     * state (ABCD)
     */
    private static long[] state = new long[4];

    /**
     * number of bits, modulo 2^64 (lsb first)
     */
    private static long[] count = new long[2];

    /**
     * input buffer
     */
    private static byte[] buffer = new byte[64];

    /**
     * digestHexStr是keyBean的唯一一个公共成员，是最新一次计算结果的 16进制ASCII表示.
     * digest,是最新一次计算结果的2进制内部表示，表示128bit的keyBean值.
     */
    private byte[] digest = new byte[16];

    /**
     * getKeyBeanOfStr是类keyBean最主要的公共方法，入口参数是你想要进行keyBean变换的字符串 返回的是变换完的结果，这个结果是从公共成员digestHexStr取得的．
     */
    String getKeyBeanOfStr(String inBuf) {
        keyBeanInit();
        keyBeanUpdate(inBuf.getBytes(), inBuf.length());
        keyBeanFinal();
        StringBuilder digestHexStr = new StringBuilder();
        int size = 16;
        for (int i = 0; i < size; i++) {
            digestHexStr.append(byteHEX(digest[i]));
        }
        return digestHexStr.toString();
    }

    private static Md5keyUtil mBean = null;

    static Md5keyUtil newInstance() {
        if (mBean == null) {
            mBean = new Md5keyUtil();
        }
        keyBeanInit();
        return mBean;
    }


    /**
     * 这是keyBean这个类的标准构造函数，JavaBean要求有一个public的并且没有参数的构造函数
     */
    private Md5keyUtil() {
        keyBeanInit();
        return;
    }

    /**
     * keyBeanInit是一个初始化函数，初始化核心变量，装入标准的幻数
     */
    private static void keyBeanInit() {
        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个基本的keyBean函数，在原始的keyBean的C实现中，由于它们是 简单的位运算，可能出于效率的考虑把它们实现成了宏，在java中，我们把它们 实现成了private方法，名字保持了原来C中的。
     */
    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将调用F,g,h,I进行近一步变换 ff, gg, hh, and ii transformations for rounds 1, 2, 3, and 4. Rotation is separate
     * from addition to prevent recomputation.
     */
    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;
    }

    /**
     * keyBeanUpdate是keyBean的主计算过程，inbuf是要变换的字节串，inputlen是长度，这个 函数由getkeyBeanofStr调用，调用之前需要调用keyBeaninit，因此把它设计成private的
     */
    private void keyBeanUpdate(byte[] inbuf, int inputLen) {
        int i, index, partLen;
        byte[] block = new byte[64];
        index = (int) (count[0] >>> 3) & 0x3F;
        // /* Update number of bits */
        int num1 = 3;
        if ((count[0] += (inputLen << num1)) < (inputLen << num1)) {
            count[1]++;
        }
        count[1] += (inputLen >>> 29);
        partLen = 64 - index;
        // Transform as many times as possible.
        int num2 = 63;
        int num3 = 64;
        if (inputLen >= partLen) {
            keyBeanMemcpy(buffer, inbuf, index, 0, partLen);
            keyBeanTransform(buffer);
            for (i = partLen; i + num2 < inputLen; i += num3) {
                keyBeanMemcpy(block, inbuf, 0, i, 64);
                keyBeanTransform(block);
            }
            index = 0;
        } else {
            i = 0;
        }
        // /* Buffer remaining input */
        keyBeanMemcpy(buffer, inbuf, index, i, inputLen - i);
    }

    /**
     * keyBeanFinal整理和填写输出结果
     */
    private void keyBeanFinal() {
        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);
        keyBeanUpdate(PADDING, padLen);
        // /* Append length (before padding) */
        keyBeanUpdate(bits, 8);
        // /* Store state in digest */
        encode(digest, state, 16);
    }

    /**
     * keyBeanMemcpy是一个内部使用的byte数组的块拷贝函数，从input的inpos开始把len长度的 字节拷贝到output的outpos位置开始
     */
    private void keyBeanMemcpy(byte[] output, byte[] input, int outpos, int inpos, int len) {
        int i;
        for (i = 0; i < len; i++) {
            output[outpos + i] = input[inpos + i];
        }
    }

    /**
     * keyBeanTransform是keyBean核心变换程序，有keyBeanUpdate调用，block是分块的原始字节
     */
    private void keyBeanTransform(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 */
        /* 1 */
        a = ff(a, b, c, d, x[0], S11, 0xd76aa478L);
        /* 2 */
        d = ff(d, a, b, c, x[1], S12, 0xe8c7b756L);
        /* 3 */
        c = ff(c, d, a, b, x[2], S13, 0x242070dbL);
        /* 4 */
        b = ff(b, c, d, a, x[3], S14, 0xc1bdceeeL);
        /* 5 */
        a = ff(a, b, c, d, x[4], S11, 0xf57c0fafL);
        /* 6 */
        d = ff(d, a, b, c, x[5], S12, 0x4787c62aL);
        /* 7 */
        c = ff(c, d, a, b, x[6], S13, 0xa8304613L);
        /* 8 */
        b = ff(b, c, d, a, x[7], S14, 0xfd469501L);
        /* 9 */
        a = ff(a, b, c, d, x[8], S11, 0x698098d8L);
        /* 10 */
        d = ff(d, a, b, c, x[9], S12, 0x8b44f7afL);
        /* 11 */
        c = ff(c, d, a, b, x[10], S13, 0xffff5bb1L);
        /* 12 */
        b = ff(b, c, d, a, x[11], S14, 0x895cd7beL);
        /* 13 */
        a = ff(a, b, c, d, x[12], S11, 0x6b901122L);
        /* 14 */
        d = ff(d, a, b, c, x[13], S12, 0xfd987193L);
        /* 15 */
        c = ff(c, d, a, b, x[14], S13, 0xa679438eL);
        /* 16 */
        b = ff(b, c, d, a, x[15], S14, 0x49b40821L);
        /* Round 2 */
        /* 17 */
        a = gg(a, b, c, d, x[1], S21, 0xf61e2562L);
        /* 18 */
        d = gg(d, a, b, c, x[6], S22, 0xc040b340L);
        /* 19 */
        c = gg(c, d, a, b, x[11], S23, 0x265e5a51L);
        /* 20 */
        b = gg(b, c, d, a, x[0], S24, 0xe9b6c7aaL);
        /* 21 */
        a = gg(a, b, c, d, x[5], S21, 0xd62f105dL);
        /* 22 */
        d = gg(d, a, b, c, x[10], S22, 0x2441453L);
        /* 23 */
        c = gg(c, d, a, b, x[15], S23, 0xd8a1e681L);
        /* 24 */
        b = gg(b, c, d, a, x[4], S24, 0xe7d3fbc8L);
        /* 25 */
        a = gg(a, b, c, d, x[9], S21, 0x21e1cde6L);
        /* 26 */
        d = gg(d, a, b, c, x[14], S22, 0xc33707d6L);
        /* 27 */
        c = gg(c, d, a, b, x[3], S23, 0xf4d50d87L);
        /* 28 */
        b = gg(b, c, d, a, x[8], S24, 0x455a14edL);
        /* 29 */
        a = gg(a, b, c, d, x[13], S21, 0xa9e3e905L);
        /* 30 */
        d = gg(d, a, b, c, x[2], S22, 0xfcefa3f8L);
        /* 31 */
        c = gg(c, d, a, b, x[7], S23, 0x676f02d9L);
        /* 32 */
        b = gg(b, c, d, a, x[12], S24, 0x8d2a4c8aL);
        /* Round 3 */
        /* 33 */
        a = hh(a, b, c, d, x[5], S31, 0xfffa3942L);
        /* 34 */
        d = hh(d, a, b, c, x[8], S32, 0x8771f681L);
        /* 35 */
        c = hh(c, d, a, b, x[11], S33, 0x6d9d6122L);
        /* 36 */
        b = hh(b, c, d, a, x[14], S34, 0xfde5380cL);
        /* 37 */
        a = hh(a, b, c, d, x[1], S31, 0xa4beea44L);
        /* 38 */
        d = hh(d, a, b, c, x[4], S32, 0x4bdecfa9L);
        /* 39 */
        c = hh(c, d, a, b, x[7], S33, 0xf6bb4b60L);
        b = hh(b, c, d, a, x[10], S34, 0xbebfbc70L);
        /* 41 */
        a = hh(a, b, c, d, x[13], S31, 0x289b7ec6L);
        /* 42 */
        d = hh(d, a, b, c, x[0], S32, 0xeaa127faL);
        /* 43 */
        c = hh(c, d, a, b, x[3], S33, 0xd4ef3085L);
        /* 44 */
        b = hh(b, c, d, a, x[6], S34, 0x4881d05L);
        /* 45 */
        a = hh(a, b, c, d, x[9], S31, 0xd9d4d039L);
        /* 46 */
        d = hh(d, a, b, c, x[12], S32, 0xe6db99e5L);
        /* 47 */
        c = hh(c, d, a, b, x[15], S33, 0x1fa27cf8L);
        /* 48 */
        b = hh(b, c, d, a, x[2], S34, 0xc4ac5665L);
        /* Round 4 */
        /* 49 */
        a = ii(a, b, c, d, x[0], S41, 0xf4292244L);
        /* 50 */
        d = ii(d, a, b, c, x[7], S42, 0x432aff97L);
        /* 51 */
        c = ii(c, d, a, b, x[14], S43, 0xab9423a7L);
        /* 52 */
        b = ii(b, c, d, a, x[5], S44, 0xfc93a039L);
        /* 53 */
        a = ii(a, b, c, d, x[12], S41, 0x655b59c3L);
        /* 54 */
        d = ii(d, a, b, c, x[3], S42, 0x8f0ccc92L);
        /* 55 */
        c = ii(c, d, a, b, x[10], S43, 0xffeff47dL);
        /* 56 */
        b = ii(b, c, d, a, x[1], S44, 0x85845dd1L);
        /* 57 */
        a = ii(a, b, c, d, x[8], S41, 0x6fa87e4fL);
        /* 58 */
        d = ii(d, a, b, c, x[15], S42, 0xfe2ce6e0L);
        /* 59 */
        c = ii(c, d, a, b, x[6], S43, 0xa3014314L);
        /* 60 */
        b = ii(b, c, d, a, x[13], S44, 0x4e0811a1L);
        /* 61 */
        a = ii(a, b, c, d, x[4], S41, 0xf7537e82L);
        /* 62 */
        d = ii(d, a, b, c, x[11], S42, 0xbd3af235L);
        /* 63 */
        c = ii(c, d, a, b, x[2], S43, 0x2ad7d2bbL);
        /* 64 */
        b = ii(b, c, d, a, x[9], S44, 0xeb86d391L);
        state[0] += a;
        state[1] += b;
        state[2] += c;
        state[3] += d;
    }

    /**
     * Encode把long数组按顺序拆成byte数组，因为java的long类型是64bit的， 只拆低32bit，以适应原始C实现的用途
     */
    private void encode(byte[] output, long[] input, int len) {
        int i, j;
        int num = 4;
        for (i = 0, j = 0; j < len; i++, j += num) {
            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数组按顺序合成成long数组，因为java的long类型是64bit的， 只合成低32bit，高32bit清零，以适应原始C实现的用途
     */
    private void decode(long[] output, byte[] input, int len) {
        int i, j;
        int num = 4;
        for (i = 0, j = 0; j < len; i++, j += num) {
            output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8) | (b2iu(input[j + 2]) << 16) | (b2iu(input[j + 3]) << 24);
        }
        return;
    }

    /**
     * b2iu是我写的一个把byte按照不考虑正负号的原则的＂升位＂程序，因为java没有unsigned运算
     */
    private static long b2iu(byte b) {
        return b < 0 ? b & 0x7F + 128 : b;
    }

    /**
     * byteHEX()，用来把一个byte类型的数转换成十六进制的ASCII表示， 因为java中的byte的toString无法实现这一点，我们又没有C语言中的 sprintf(outbuf,"%02X",ib)
     */
    private 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];
        return new String(ob);
    }
}