#include "md5.h"
#include <string.h>

/*
 * MD5 实现（照手表 smartwatchbootloader 的 MD5 库搬运）
 * 注意：手表原文件用 memcpy 但没 include <string.h>，这里补上。
 */

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 int 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 int 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 int 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); /* 1 */
    FF(d, a, b, c, x[ 1], 12, 0xe8c7b756); /* 2 */
    FF(c, d, a, b, x[ 2], 17, 0x242070db); /* 3 */
    FF(b, c, d, a, x[ 3], 22, 0xc1bdceee); /* 4 */
    FF(a, b, c, d, x[ 4], 7, 0xf57c0faf); /* 5 */
    FF(d, a, b, c, x[ 5], 12, 0x4787c62a); /* 6 */
    FF(c, d, a, b, x[ 6], 17, 0xa8304613); /* 7 */
    FF(b, c, d, a, x[ 7], 22, 0xfd469501); /* 8 */
    FF(a, b, c, d, x[ 8], 7, 0x698098d8); /* 9 */
    FF(d, a, b, c, x[ 9], 12, 0x8b44f7af); /* 10 */
    FF(c, d, a, b, x[10], 17, 0xffff5bb1); /* 11 */
    FF(b, c, d, a, x[11], 22, 0x895cd7be); /* 12 */
    FF(a, b, c, d, x[12], 7, 0x6b901122); /* 13 */
    FF(d, a, b, c, x[13], 12, 0xfd987193); /* 14 */
    FF(c, d, a, b, x[14], 17, 0xa679438e); /* 15 */
    FF(b, c, d, a, x[15], 22, 0x49b40821); /* 16 */

    /* Round 2 */
    GG(a, b, c, d, x[ 1], 5, 0xf61e2562); /* 17 */
    GG(d, a, b, c, x[ 6], 9, 0xc040b340); /* 18 */
    GG(c, d, a, b, x[11], 14, 0x265e5a51); /* 19 */
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa); /* 20 */
    GG(a, b, c, d, x[ 5], 5, 0xd62f105d); /* 21 */
    GG(d, a, b, c, x[10], 9, 0x2441453); /* 22 */
    GG(c, d, a, b, x[15], 14, 0xd8a1e681); /* 23 */
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8); /* 24 */
    GG(a, b, c, d, x[ 9], 5, 0x21e1cde6); /* 25 */
    GG(d, a, b, c, x[14], 9, 0xc33707d6); /* 26 */
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87); /* 27 */
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed); /* 28 */
    GG(a, b, c, d, x[13], 5, 0xa9e3e905); /* 29 */
    GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8); /* 30 */
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9); /* 31 */
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a); /* 32 */

    /* Round 3 */
    HH(a, b, c, d, x[ 5], 4, 0xfffa3942); /* 33 */
    HH(d, a, b, c, x[ 8], 11, 0x8771f681); /* 34 */
    HH(c, d, a, b, x[11], 16, 0x6d9d6122); /* 35 */
    HH(b, c, d, a, x[14], 23, 0xfde5380c); /* 36 */
    HH(a, b, c, d, x[ 1], 4, 0xa4beea44); /* 37 */
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9); /* 38 */
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60); /* 39 */
    HH(b, c, d, a, x[10], 23, 0xbebfbc70); /* 40 */
    HH(a, b, c, d, x[13], 4, 0x289b7ec6); /* 41 */
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa); /* 42 */
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085); /* 43 */
    HH(b, c, d, a, x[ 6], 23, 0x4881d05); /* 44 */
    HH(a, b, c, d, x[ 9], 4, 0xd9d4d039); /* 45 */
    HH(d, a, b, c, x[12], 11, 0xe6db99e5); /* 46 */
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8); /* 47 */
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665); /* 48 */

    /* Round 4 */
    II(a, b, c, d, x[ 0], 6, 0xf4292244); /* 49 */
    II(d, a, b, c, x[ 7], 10, 0x432aff97); /* 50 */
    II(c, d, a, b, x[14], 15, 0xab9423a7); /* 51 */
    II(b, c, d, a, x[ 5], 21, 0xfc93a039); /* 52 */
    II(a, b, c, d, x[12], 6, 0x655b59c3); /* 53 */
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92); /* 54 */
    II(c, d, a, b, x[10], 15, 0xffeff47d); /* 55 */
    II(b, c, d, a, x[ 1], 21, 0x85845dd1); /* 56 */
    II(a, b, c, d, x[ 8], 6, 0x6fa87e4f); /* 57 */
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0); /* 58 */
    II(c, d, a, b, x[ 6], 15, 0xa3014314); /* 59 */
    II(b, c, d, a, x[13], 21, 0x4e0811a1); /* 60 */
    II(a, b, c, d, x[ 4], 6, 0xf7537e82); /* 61 */
    II(d, a, b, c, x[11], 10, 0xbd3af235); /* 62 */
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb); /* 63 */
    II(b, c, d, a, x[ 9], 21, 0xeb86d391); /* 64 */

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