/* md5.c - Don Yang (uguu.org)

   Cleaned up version of reference implementation from RFC 1321.

   12/27/05
                                                                           */
/*@ -mustdefine -type @*/

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

#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 RotateLeft(x, n)   (((x) << (n)) | ((x) >> (32 - (n))))

#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 FF(a, b, c, d, x, s, ac) \
   (a) += F((b), (c), (d)) + (x) + (uint32)(ac); \
   (a) = RotateLeft((a), (s)); \
   (a) += (b);
#define GG(a, b, c, d, x, s, ac) \
   (a) += G((b), (c), (d)) + (x) + (uint32)(ac); \
   (a) = RotateLeft((a), (s)); \
   (a) += (b);
#define HH(a, b, c, d, x, s, ac) \
   (a) += H((b), (c), (d)) + (x) + (uint32)(ac); \
   (a) = RotateLeft((a), (s)); \
   (a) += (b);
#define II(a, b, c, d, x, s, ac) \
   (a) += I((b), (c), (d)) + (x) + (uint32)(ac); \
   (a) = RotateLeft((a), (s)); \
   (a) += (b);

static void Decode(/*@out@*/uint32 *output, byte *input, uint32 length)
{
   uint32 i, j;

   for(i = j = 0; j < length; i++, j += 4)
   {
      output[i] =
         ((uint32)input[j]) |
         (((uint32)input[j + 1]) << 8) |
         (((uint32)input[j + 2]) << 16) |
         (((uint32)input[j + 3]) << 24);
   }
}

static void Encode(/*@out@*/byte *output, uint32 *input, uint32 length)
{
   uint32 i, j;

   for(i = j = 0; j < length; i++, j += 4)
   {
      output[j] = (byte)(input[i] & 0xff);
      output[j + 1] = (byte)((input[i] >> 8) & 0xff);
      output[j + 2] = (byte)((input[i] >> 16) & 0xff);
      output[j + 3] = (byte)((input[i] >> 24) & 0xff);
   }
}

static void MD5Transform(uint32 *state, byte *block)
{
   uint32 a, b, c, d, x[16];

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

   Decode(x, block, 64);

   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);

   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);

   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);

   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(/*@out@*/MD5_CTX *context)
{
   context->size[0] = context->size[1] = 0;
   context->state[0] = 0x67452301;
   context->state[1] = 0xefcdab89;
   context->state[2] = 0x98badcfe;
   context->state[3] = 0x10325476;
}

void MD5Update(MD5_CTX *context, byte *input, uint32 length)
{
   uint32 i, index, plength;

   index = ((context->size[0] >> 3) & 0x3f);
   if( (context->size[0] += (length << 3)) < (length << 3) )
      context->size[1]++;
   context->size[1] += (length >> 29);

   plength = 64 - index;

   if( length >= plength )
   {
      memcpy(&context->block[index], input, (size_t)plength);
      MD5Transform(context->state, context->block);

      for(i = plength; i + 63 < length; i += 64)
         MD5Transform(context->state, input + i);
      index = 0;
   }
   else
   {
      i = 0;
   }

   memcpy(&context->block[index], input + i, (size_t)(length - i));
}

void MD5Final(/*@out@*/byte *digest, MD5_CTX *context)
{
   static byte padding[64] = {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};
   byte bits[8];
   uint32 index, padlength;

   Encode(bits, context->size, 8);

   index = ((context->size[0] >> 3) & 0x3f);
   padlength = (index < 56) ? (56 - index) : (120 - index);
   MD5Update(context, padding, padlength);
   MD5Update(context, bits, 8);

   Encode(digest, context->state, 16);
}