arithtst.c

常用的无损压缩算法源代码

/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */

/*     A R I T H M E T I C   C O D E   I M P L E M E N T A T I O N     */

/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */
/*     > > > > >    ANSI C version  4.03  -  05/30/95    < < < < <     */

/*   Amir Said - [e-mail]                            */
/*   Faculty of Electrical Engineering                                 */
/*   University of Campinas (UNICAMP) - Campinas, SP 13081, Brazil     */

/*   William A. Pearlman - [e-mail]                       */
/*   Dept. of Electrical, Computer, and Systems Engineering            */
/*   Rensselaer Polytechnic Institute - Troy, NY 12180, USA            */


/* - - Inclusion - - - - - - - - - - - - - - - - - - - - - - - - - - - */

#include "arithm.h"


/* - - Definitions - - - - - - - - - - - - - - - - - - - - - - - - - - */

int Random(int n);    /* Portable pseudo-random numbers generator      */
                      /* returns integer in the interval [0,n-1]       */
                      /* nonuniform distribution                       */

void SRand(long);

long seed_1, seed_2;


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* - - Main function - - - - - - - - - - - - - - - - - - - - - - - - - */

int main(void)
{

  Adaptive_Model model1, model2;
  Encoder enc;
  Decoder dec;

  int i, j, k;
  long  nb;


/* Random message coding */


  Create_Model(&model1, 5);      /* initialize statistics and define */
  Create_Model(&model2, 15);     /* alphabet size = 5 and 15         */

  Start_Encoder(&enc, "test.cod");  /* initialize encoder, open file */

  SRand(111);         /* set random number generator for coding test */

  for (i = 0; i < 500; i++) {
    k = Random(5);                    /* get random data symbol      */
    Write_Symbol(&enc, &model1, k);   /* code symbol with "model1"   */
    k = Random(15);                   /* get random data symbol      */
    Write_Symbol(&enc, &model2, k);   /* code symbol with "model2"   */
    k = Random(32);                   /* get random data symbol      */
    Write_Bits(&enc, 5, k); }         /* code 5 bits (uniform model) */


  Set_New_Model(&model1, 2);         /* reset models and define new  */
  Set_New_Model(&model2, 4);         /* alphabet size = 2 and 4      */

  for (i = 0; i < 500; i++) {        /* code new random data symbols */
    k = Random(2);
    Write_Symbol(&enc, &model1, k);
    k = Random(4);
    Write_Symbol(&enc, &model2, k); }

  Stop_Encoder(&enc);                  /* close encoded message file */

  nb = Bytes_Used(&enc);                /* bytes used in the message */

  printf(" Coded message has %ld bytes.",  nb);


/* Message decoding and testing */

  Start_Decoder(&dec, "test.cod"); /* initialize decoder, open file */

  Set_New_Model(&model1, 5);      /* duplicate encoder's definitions */
  Set_New_Model(&model2, 15);

  SRand(111);       /* set random number generator for decoding test */

  for (i = 0; i < 500; i++) {
    k = Random(5);
    j = Read_Symbol(&dec, &model1);   /* decode symbol with "model1" */

    if (j != k)                       /* test decoded symbol         */
      puts("\aDecoding error!");

    k = Random(15);
    j = Read_Symbol(&dec, &model2);   /* decode symbol with "model2" */

    if (j != k)                       /* test decoded symbol         */
      puts("\aDecoding error!"); 

    k = Random(32);
    j = Read_Bits(&dec, 5);           /* decode 5 bits               */

    if (j != k)                       /* test decoded symbol         */
      puts("\aDecoding error!"); }


  Set_New_Model(&model1, 2);          /* reset and define new models */
  Set_New_Model(&model2, 4);

  for (i = 0; i < 500; i++) { /* decode next symbols with new models */
    k = Random(2);
    j = Read_Symbol(&dec, &model1);

    if (j != k)
      puts("\aDecoding error!");

    k = Random(4);
    j = Read_Symbol(&dec, &model2);
    if (j != k)
      puts("\aDecoding error!"); }

  printf("\n\n End of the arithmetic coding test.\n\n");

  return 0;
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* - - Implementations of the random generator - - - - - - - - - - - - */

int Random(int n)
{
  long z, k;
  double t;
  k = seed_1 / 53668L;
  seed_1 = 40014L * (seed_1 - k * 53668L) - k * 12211L;
  if (seed_1 < 0L) seed_1 += 2147483563L;
  k = seed_2 / 52774L;
  seed_2 = 40692L * (seed_2 - k * 52774L) - k * 3791L;
  if (seed_2 < 0L) seed_2 += 2147483399L;
  z = seed_1 - seed_2;
  if (z < 1) z += 2147483562L;
  t = 4.656613e-10 * z;
  return (int) (n * t * t);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

void SRand(long s)
{
  seed_1 = s;  seed_2 = 2147483399L - s;
}

/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */

/* end of file < arithtst.c > */