#include "md5.h"

unsigned char PADDING[] = {
    0x80, 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 };

void MD5Init(MD5_CTX *context)
{
    context->count[0] = 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, unsigned char *input, unsigned long inputlen)
{
    unsigned int i = 0, index = 0, partlen = 0;
    index = (context->count[0] >> 3) & 0x3F;
    partlen = 64 - index;
    context->count[0] += inputlen << 3;
    if (context->count[0] < (inputlen << 3))
        context->count[1]++;
    context->count[1] += inputlen >> 29;
    
    if (inputlen >= partlen)
    {
        memcpy(&context->buffer[index], input, partlen);
        MD5Transform(context->state, context->buffer);
        for (i = partlen; i + 64 <= inputlen; i += 64)
            MD5Transform(context->state, &input[i]);
        index = 0;
    }
    else
    {
        i = 0;
    }
    memcpy(&context->buffer[index], &input[i], inputlen - i);
}

void MD5Final(MD5_CTX *context, unsigned char digest[16])
{
    unsigned int index = 0, padlen = 0;
    unsigned char bits[8];
    index = (context->count[0] >> 3) & 0x3F;
    padlen = (index < 56) ? (56 - index) : (120 - index);
    MD5Encode(bits, context->count, 8);
    MD5Update(context, PADDING, padlen);
    MD5Update(context, bits, 8);
    MD5Encode(digest, context->state, 16);
}

void MD5Encode(unsigned char *output, unsigned int *input, unsigned long len)
{
    unsigned int i = 0, j = 0;
    while (j < len)
    {
        output[j] = input[i] & 0xFF;
        output[j + 1] = (input[i] >> 8) & 0xFF;
        output[j + 2] = (input[i] >> 16) & 0xFF;
        output[j + 3] = (input[i] >> 24) & 0xFF;
        i++;
        j += 4;
    }
}

void MD5Decode(unsigned int *output, unsigned char *input, unsigned long len)
{
    unsigned int i = 0, j = 0;
    while (j < len)
    {
        output[i] = (input[j]) |
        (input[j + 1] << 8) |
        (input[j + 2] << 16) |
        (input[j + 3] << 24);
        i++;
        j += 4;
    }
}

void MD5Transform(unsigned int state[4], unsigned char block[64])
{
    unsigned int a = state[0];
    unsigned int b = state[1];
    unsigned int c = state[2];
    unsigned int d = state[3];
    unsigned int x[64];
    
    MD5Decode(x, block, 64);
    FF(a, b, c, d, x[0], 7, 0xd76aa478);
    FF(d, a, b, c, x[1], 12, 0xe8c7b756);
    FF(c, d, a, b, x[2], 17, 0x242070db);
    FF(b, c, d, a, x[3], 22, 0xc1bdceee);
    FF(a, b, c, d, x[4], 7, 0xf57c0faf);
    FF(d, a, b, c, x[5], 12, 0x4787c62a);
    FF(c, d, a, b, x[6], 17, 0xa8304613);
    FF(b, c, d, a, x[7], 22, 0xfd469501);
    FF(a, b, c, d, x[8], 7, 0x698098d8);
    FF(d, a, b, c, x[9], 12, 0x8b44f7af);
    FF(c, d, a, b, x[10], 17, 0xffff5bb1);
    FF(b, c, d, a, x[11], 22, 0x895cd7be);
    FF(a, b, c, d, x[12], 7, 0x6b901122);
    FF(d, a, b, c, x[13], 12, 0xfd987193);
    FF(c, d, a, b, x[14], 17, 0xa679438e);
    FF(b, c, d, a, x[15], 22, 0x49b40821);
    
    
    GG(a, b, c, d, x[1], 5, 0xf61e2562);
    GG(d, a, b, c, x[6], 9, 0xc040b340);
    GG(c, d, a, b, x[11], 14, 0x265e5a51);
    GG(b, c, d, a, x[0], 20, 0xe9b6c7aa);
    GG(a, b, c, d, x[5], 5, 0xd62f105d);
    GG(d, a, b, c, x[10], 9, 0x2441453);
    GG(c, d, a, b, x[15], 14, 0xd8a1e681);
    GG(b, c, d, a, x[4], 20, 0xe7d3fbc8);
    GG(a, b, c, d, x[9], 5, 0x21e1cde6);
    GG(d, a, b, c, x[14], 9, 0xc33707d6);
    GG(c, d, a, b, x[3], 14, 0xf4d50d87);
    GG(b, c, d, a, x[8], 20, 0x455a14ed);
    GG(a, b, c, d, x[13], 5, 0xa9e3e905);
    GG(d, a, b, c, x[2], 9, 0xfcefa3f8);
    GG(c, d, a, b, x[7], 14, 0x676f02d9);
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);
    
    
    HH(a, b, c, d, x[5], 4, 0xfffa3942);
    HH(d, a, b, c, x[8], 11, 0x8771f681);
    HH(c, d, a, b, x[11], 16, 0x6d9d6122);
    HH(b, c, d, a, x[14], 23, 0xfde5380c);
    HH(a, b, c, d, x[1], 4, 0xa4beea44);
    HH(d, a, b, c, x[4], 11, 0x4bdecfa9);
    HH(c, d, a, b, x[7], 16, 0xf6bb4b60);
    HH(b, c, d, a, x[10], 23, 0xbebfbc70);
    HH(a, b, c, d, x[13], 4, 0x289b7ec6);
    HH(d, a, b, c, x[0], 11, 0xeaa127fa);
    HH(c, d, a, b, x[3], 16, 0xd4ef3085);
    HH(b, c, d, a, x[6], 23, 0x4881d05);
    HH(a, b, c, d, x[9], 4, 0xd9d4d039);
    HH(d, a, b, c, x[12], 11, 0xe6db99e5);
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
    HH(b, c, d, a, x[2], 23, 0xc4ac5665);
    
    
    II(a, b, c, d, x[0], 6, 0xf4292244);
    II(d, a, b, c, x[7], 10, 0x432aff97);
    II(c, d, a, b, x[14], 15, 0xab9423a7);
    II(b, c, d, a, x[5], 21, 0xfc93a039);
    II(a, b, c, d, x[12], 6, 0x655b59c3);
    II(d, a, b, c, x[3], 10, 0x8f0ccc92);
    II(c, d, a, b, x[10], 15, 0xffeff47d);
    II(b, c, d, a, x[1], 21, 0x85845dd1);
    II(a, b, c, d, x[8], 6, 0x6fa87e4f);
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
    II(c, d, a, b, x[6], 15, 0xa3014314);
    II(b, c, d, a, x[13], 21, 0x4e0811a1);
    II(a, b, c, d, x[4], 6, 0xf7537e82);
    II(d, a, b, c, x[11], 10, 0xbd3af235);
    II(c, d, a, b, x[2], 15, 0x2ad7d2bb);
    II(b, c, d, a, x[9], 21, 0xeb86d391);
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}