text: /**
  *  $Id: md5.c,v 1.2 2008/03/24 20:59:12 mascarenhas Exp $
  *  Hash function MD5
  *  @author  Marcela Ozorio Suarez, Roberto I.
  */
  
  
  #include <string.h>
  
  #include "md5.h"
  
  
  #define WORD 32
  #define MASK 0xFFFFFFFF
  #if __STDC_VERSION__ >= 199901L
  #include <stdint.h>
  typedef uint32_t WORD32;
  #else
  typedef unsigned int WORD32;
  #endif
  
  
  /**
  *  md5 hash function.
  *  @param message: aribtary string.
  *  @param len: message length.
  *  @param output: buffer to receive the hash value. Its size must be
  *  (at least) HASHSIZE.
  */
  void md5 (const char *message, long len, char *output);
  
  
  
  /*
  ** Realiza a rotacao no sentido horario dos bits da variavel 'D' do tipo WORD32.
  ** Os bits sao deslocados de 'num' posicoes
  */
  #define rotate(D, num)  (D<<num) | (D>>(WORD-num))
  
  /*Macros que definem operacoes relizadas pelo algoritmo  md5 */
  #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))))
  
  
  /*vetor de numeros utilizados pelo algoritmo md5 para embaralhar bits */
  static const WORD32 T[64]={
          0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
          0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
          0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
          0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
          0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
          0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
          0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
          0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
          0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
          0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
          0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
          0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
          0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
          0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
          0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
          0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
  };
  
  
  static void word32tobytes (const WORD32 *input, char *output) {
      int j = 0;
      while (j<4*4) {
          WORD32 v = *input++;
          output[j++] = (char)(v & 0xff); v >>= 8;
          output[j++] = (char)(v & 0xff); v >>= 8;
          output[j++] = (char)(v & 0xff); v >>= 8;
          output[j++] = (char)(v & 0xff);
      }
  }
  
  
  static void inic_digest(WORD32 *d) {
      d[0] = 0x67452301;
      d[1] = 0xEFCDAB89;
      d[2] = 0x98BADCFE;
      d[3] = 0x10325476;
  }
  
  
  /*funcao que implemeta os quatro passos principais do algoritmo MD5 */
  static void digest(const WORD32 *m, WORD32 *d) {
      int j;
      /*MD5 PASSO1 */
      for (j=0; j<4*4; j+=4) {
          d[0] = d[0]+ F(d[1], d[2], d[3])+ m[j] + T[j];       d[0]=rotate(d[0], 7);
          d[0]+=d[1];
          d[3] = d[3]+ F(d[0], d[1], d[2])+ m[(j)+1] + T[j+1]; d[3]=rotate(d[3], 12);
          d[3]+=d[0];
          d[2] = d[2]+ F(d[3], d[0], d[1])+ m[(j)+2] + T[j+2]; d[2]=rotate(d[2], 17);
          d[2]+=d[3];
          d[1] = d[1]+ F(d[2], d[3], d[0])+ m[(j)+3] + T[j+3]; d[1]=rotate(d[1], 22);
          d[1]+=d[2];
      }
      /*MD5 PASSO2 */
      for (j=0; j<4*4; j+=4) {
          d[0] = d[0]+ G(d[1], d[2], d[3])+ m[(5*j+1)&0x0f] + T[(j-1)+17];
          d[0] = rotate(d[0],5);
          d[0]+=d[1];
          d[3] = d[3]+ G(d[0], d[1], d[2])+ m[((5*(j+1)+1)&0x0f)] + T[(j+0)+17];
          d[3] = rotate(d[3], 9);
          d[3]+=d[0];
          d[2] = d[2]+ G(d[3], d[0], d[1])+ m[((5*(j+2)+1)&0x0f)] + T[(j+1)+17];
          d[2] = rotate(d[2], 14);
          d[2]+=d[3];
          d[1] = d[1]+ G(d[2], d[3], d[0])+ m[((5*(j+3)+1)&0x0f)] + T[(j+2)+17];
          d[1] = rotate(d[1], 20);
          d[1]+=d[2];
      }
      /*MD5 PASSO3 */
      for (j=0; j<4*4; j+=4) {
          d[0] = d[0]+ H(d[1], d[2], d[3])+ m[(3*j+5)&0x0f] + T[(j-1)+33];
          d[0] = rotate(d[0], 4);
          d[0]+=d[1];
          d[3] = d[3]+ H(d[0], d[1], d[2])+ m[(3*(j+1)+5)&0x0f] + T[(j+0)+33];
          d[3] = rotate(d[3], 11);
          d[3]+=d[0];
          d[2] = d[2]+ H(d[3], d[0], d[1])+ m[(3*(j+2)+5)&0x0f] + T[(j+1)+33];
          d[2] = rotate(d[2], 16);
          d[2]+=d[3];
          d[1] = d[1]+ H(d[2], d[3], d[0])+ m[(3*(j+3)+5)&0x0f] + T[(j+2)+33];
          d[1] = rotate(d[1], 23);
          d[1]+=d[2];
      }
      /*MD5 PASSO4 */
      for (j=0; j<4*4; j+=4) {
          d[0] = d[0]+ I(d[1], d[2], d[3])+ m[(7*j)&0x0f] + T[(j-1)+49];
          d[0] = rotate(d[0], 6);
          d[0]+=d[1];
          d[3] = d[3]+ I(d[0], d[1], d[2])+ m[(7*(j+1))&0x0f] + T[(j+0)+49];
          d[3] = rotate(d[3], 10);
          d[3]+=d[0];
          d[2] = d[2]+ I(d[3], d[0], d[1])+ m[(7*(j+2))&0x0f] + T[(j+1)+49];
          d[2] = rotate(d[2], 15);
          d[2]+=d[3];
          d[1] = d[1]+ I(d[2], d[3], d[0])+ m[(7*(j+3))&0x0f] + T[(j+2)+49];
          d[1] = rotate(d[1], 21);
          d[1]+=d[2];
      }
  }
  
  
  static void bytestoword32 (WORD32 *x, const char *pt) {
      int i;
      for (i=0; i<16; i++) {
          int j=i*4;
          x[i] = (((WORD32)(unsigned char)pt[j+3] << 8 |
                   (WORD32)(unsigned char)pt[j+2]) << 8 |
                  (WORD32)(unsigned char)pt[j+1]) << 8 |
                 (WORD32)(unsigned char)pt[j];
      }
  
  }
  
  
  static void put_length(WORD32 *x, long len) {
      /* in bits! */
      x[14] = (WORD32)((len<<3) & MASK);
      x[15] = (WORD32)(len>>(32-3) & 0x7);
  }
  
  
  /*
  ** returned status:
  *  0 - normal message (full 64 bytes)
  *  1 - enough room for 0x80, but not for message length (two 4-byte words)
  *  2 - enough room for 0x80 plus message length (at least 9 bytes free)
  */
  static int converte (WORD32 *x, const char *pt, int num, int old_status) {
      int new_status = 0;
      char buff[64];
      if (num<64) {
          memcpy(buff, pt, num);  /* to avoid changing original string */
          memset(buff+num, 0, 64-num);
          if (old_status == 0)
              buff[num] = '\200';
          new_status = 1;
          pt = buff;
      }
      bytestoword32(x, pt);
      if (num <= (64 - 9))
          new_status = 2;
      return new_status;
  }
  
  
  
  void md5 (const char *message, long len, char *output) {
      WORD32 d[4];
      int status = 0;
      long i = 0;
      inic_digest(d);
      while (status != 2) {
          WORD32 d_old[4];
          WORD32 wbuff[16];
          int numbytes = (len-i >= 64) ? 64 : len-i;
          /*salva os valores do vetor digest*/
          d_old[0]=d[0]; d_old[1]=d[1]; d_old[2]=d[2]; d_old[3]=d[3];
          status = converte(wbuff, message+i, numbytes, status);
          if (status == 2) put_length(wbuff, len);
          digest(wbuff, d);
          d[0]+=d_old[0]; d[1]+=d_old[1]; d[2]+=d_old[2]; d[3]+=d_old[3];
          i += numbytes;
      }
      word32tobytes(d, output);
  }
  