Source code in the pari/gp programming language

#include 
#include 

#define HEX(x)  (((x) < 10)? (x)+'0': (x)-10+'a')

/*
 * PARI/GP func: MD5 hash
 *
 * gp code: install("plug_md5", "s", "MD5", "");
 */
GEN plug_md5(char *text)
{
  char md[MD5_DIGEST_LENGTH];
  char hash[sizeof(md) * 2 + 1];
  int i;

  MD5((unsigned char*)text, strlen(text), (unsigned char*)md);

  for (i = 0; i < sizeof(md); i++) {
    hash[i+i]   = HEX((md[i] >> 4) & 0x0f);
    hash[i+i+1] = HEX(md[i] & 0x0f);
  }

  hash[sizeof(md) * 2] = 0;

  return strtoGENstr(hash);
}


install("plug_md5", "s", "MD5", "~/libmd5.so");

MD5("The quick brown fox jumped over the lazy dog's back")

md5( message ) = { my( 
   a = 0x67452301, b = 0xefcdab89, c = 0x98badcfe, d = 0x10325476,
   s = [ 7, 12, 17, 22; 5, 9, 14, 20; 4, 11, 16, 23; 6, 10, 15, 21 ],
   msg = concat( Vec( concat(Vecsmall(message), Vecsmall(128)), (#message + 9) \ 64 * 64 + 56 ),
     Vecrev(digits( #message % 2^61 * 8, 256), 8)), \\ little endian !
   leftrotate(x, c) = x << c + x >> (32-c)
  );
  \\***  Process the message in successive 512-bit chunks ***
  forstep( m=1, #msg, 512/8, 
    my( \\ break chunk into 32-bit words M[j] - LITTLE ENDIAN !
       M = vector( 16, j, fromdigits( Vecrev(msg[ m + j*4 - 4 .. m + j*4 - 1 ]), 2^8 )),
       A = a, B = b, C = c, D = d); 
    for( i = 0 , 63 , [A, D, C, B] = [D, C, B, B + leftrotate( ( A + abs(sin(i+1))\2^-32 +
       if( i < 16 , bitor( bitand(B , C) , bitand( bitneg(B) , D)) + M[ i +1]
         , i < 32 , bitor( bitand(D , B) , bitand( bitneg(D) , C)) + M[ (5*i + 1) % 16 +1]
         , i < 48 , bitxor( bitxor( B , C ) , D ) + M[ (3*i + 5) % 16 +1]
         , bitxor( C , bitor( bitneg(D), B)) + M[ 7*i % 16 +1]
       )) % 2^32, s[i\16+1, i%4+1] )]
    ); \\ end for
    [a,b,c,d] = ([a,b,c,d] + [A,B,C,D]) % 2^32 ;
  ); \\ end forstep
  Strprintf("%032x",fromdigits(Vecrev(digits(fromdigits([d,c,b,a],2^32),256),16),256))
}

gp > md5("")

gp > md5("The quick brown fox jumps over lazy dogs.")