#include "tiny_md5.h"
#include <string.h>
MD5_CTX context;

// 常量表
static const uint8_t PADDING[64] = {
  0x80
};

static void Encode(uint8_t* output, const uint32_t* input, uint32_t len) {
    for (uint32_t i = 0, j = 0; j < len; i++, j += 4) {
        output[j] = (uint8_t)(input[i] & 0xff);
        output[j+1] = (uint8_t)((input[i] >> 8) & 0xff);
        output[j+2] = (uint8_t)((input[i] >> 16) & 0xff);
        output[j+3] = (uint8_t)((input[i] >> 24) & 0xff);
    }
}

static void MD5Transform(uint32_t state[4], const uint8_t block[64]);

void MD5_Calculate(uint8_t* input, uint32_t length, uint8_t output[16]) {
    
    MD5Init(&context);
    MD5Update(&context, input, length);
    MD5Final(output, &context);
}

/* 下面是核心实现 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

#define F(x,y,z) (((x)&(y)) | ((~x)&(z)))
#define G(x,y,z) (((x)&(z)) | ((y)&(~z)))
#define H(x,y,z) ((x) ^ (y) ^ (z))
#define I(x,y,z) ((y) ^ ((x) | (~z)))

#define ROTATE_LEFT(x,n) (((x) << (n)) | ((x) >> (32-(n))))

#define FF(a,b,c,d,x,s,ac) { \
 (a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define GG(a,b,c,d,x,s,ac) { \
 (a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define HH(a,b,c,d,x,s,ac) { \
 (a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}
#define II(a,b,c,d,x,s,ac) { \
 (a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
}

static void MD5Transform(uint32_t state[4], const uint8_t block[64]) {
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];
    memcpy(x, block, 64);

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

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

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

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

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

void MD5Init(MD5_CTX* context) {
    context->count[0] = context->count[1] = 0;
    context->state[0] = 0x67452301;
    context->state[1] = 0xefcdab89;
    context->state[2] = 0x98badcfe;
    context->state[3] = 0x10325476;
}

void MD5Update(MD5_CTX* context, const uint8_t* input, uint32_t inputLen) {
    uint32_t i, index, partLen;

    index = (context->count[0] >> 3) & 0x3F;
    context->count[0] += inputLen << 3;
    if (context->count[0] < (inputLen << 3))
        context->count[1]++;
    context->count[1] += inputLen >> 29;

    partLen = 64 - index;
    if (inputLen >= partLen) {
        memcpy(&context->buffer[index], input, partLen);
        MD5Transform(context->state, context->buffer);
        for (i = partLen; i + 63 < inputLen; i += 64)
            MD5Transform(context->state, &input[i]);
        index = 0;
    } else {
        i = 0;
    }

    memcpy(&context->buffer[index], &input[i], inputLen - i);
}

void MD5Final(uint8_t digest[16], MD5_CTX* context) {
    uint8_t bits[8];
    uint32_t index, padLen;
    Encode(bits, context->count, 8);
    index = (context->count[0] >> 3) & 0x3f;
    padLen = (index < 56) ? (56 - index) : (120 - index);
    MD5Update(context, PADDING, padLen);
    MD5Update(context, bits, 8);
    Encode(digest, context->state, 16);
}