rstest.c

/* Test the Reed-Solomon codecs
 * for various block sizes and with random data and random error patterns
 *
 * Copyright 2002 Phil Karn, KA9Q
 * May be used under the terms of the GNU Lesser General Public License (LGPL)
 */

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <time.h>
#include "fec.h"


struct etab {
  int symsize;
  int genpoly;
  int fcs;
  int prim;
  int nroots;
  int ntrials;
} Tab[] = {
  {2, 0x7,     1,   1, 1, 10 },
  {3, 0xb,     1,   1, 2, 10 },
  {4, 0x13,    1,   1, 4, 10 },
  {5, 0x25,    1,   1, 6, 10 },
  {6, 0x43,    1,   1, 8, 10 },
  {7, 0x89,    1,   1, 10, 10 },
  {8, 0x11d,   1,   1, 32, 10 },
  {8, 0x187,   112,11, 32, 10 }, /* Duplicates CCSDS codec */
  {9, 0x211,   1,   1, 32, 10 },
  {10,0x409,   1,   1, 32, 10 },
  {11,0x805,   1,   1, 32, 10 },
  {12,0x1053,  1,   1, 32, 5 },
  {13,0x201b,  1,   1, 32, 2 },
  {14,0x4443,  1,   1, 32, 1 },
  {15,0x8003,  1,   1, 32, 1 },
  {16,0x1100b, 1,   1, 32, 1 },
  {0, 0, 0, 0, 0},
};

int exercise_char(struct etab *e);
int exercise_int(struct etab *e);
int exercise_8(void);

int main(){
  int i;

  srandom(time(NULL));

  printf("Testing fixed CCSDS encoder...\n");
  exercise_8();
  for(i=0;Tab[i].symsize != 0;i++){
    int nn,kk;

    nn = (1<<Tab[i].symsize) - 1;
    kk = nn - Tab[i].nroots;
    printf("Testing (%d,%d) code...\n",nn,kk);
    if(Tab[i].symsize <= 8)
      exercise_char(&Tab[i]);
    else
      exercise_int(&Tab[i]);
  }
  exit(0);
}

int exercise_8(void){
  int nn = 255;
  unsigned char block[nn],tblock[nn];
  int errlocs[nn],derrlocs[nn];
  int i;
  int errors;
  int derrors,kk;
  int errval,errloc;
  int erasures;
  int decoder_errors = 0;

  /* Compute code parameters */
  kk = 223;


  /* Test up to the error correction capacity of the code */
  for(errors=0;errors<=(nn-kk)/2;errors++){

    /* Load block with random data and encode */
    for(i=0;i<kk;i++)
      block[i] = random() & nn;
    memcpy(tblock,block,sizeof(block));
    encode_rs_8(block,&block[kk],0);

    /* Make temp copy, seed with errors */
    memcpy(tblock,block,sizeof(block));
    memset(errlocs,0,sizeof(errlocs));
    memset(derrlocs,0,sizeof(derrlocs));
    erasures=0;
    for(i=0;i<errors;i++){
      do {
	errval = random() & nn;
      } while(errval == 0); /* Error value must be nonzero */
      
      do {
	errloc = random() % nn;
      } while(errlocs[errloc] != 0); /* Must not choose the same location twice */
      
      errlocs[errloc] = 1;

#if FLAG_ERASURE
      if(random() & 1) /* 50-50 chance */
	derrlocs[erasures++] = errloc;
#endif
      tblock[errloc] ^= errval;
    }

    /* Decode the errored block */
    derrors = decode_rs_8(tblock,derrlocs,erasures,0);

    if(derrors != errors){
	printf("(%d,%d) decoder says %d errors, true number is %d\n",nn,kk,derrors,errors);
	decoder_errors++;
    }
    for(i=0;i<derrors;i++){
      if(errlocs[derrlocs[i]] == 0){
	printf("(%d,%d) decoder indicates error in location %d without error\n",nn,kk,derrlocs[i]);
	decoder_errors++;
      }
    }
    if(memcmp(tblock,block,sizeof(tblock)) != 0){
      printf("(%d,%d) decoder uncorrected errors! output ^ input:",nn,kk);
      decoder_errors++;
      for(i=0;i<nn;i++)
	printf(" %02x",tblock[i] ^ block[i]);
      printf("\n");
    }
  }
  return decoder_errors;
}


int exercise_char(struct etab *e){
  int nn = (1<<e->symsize) - 1;
  unsigned char block[nn],tblock[nn];
  int errlocs[nn],derrlocs[nn];
  int i;
  int errors;
  int derrors,kk;
  int errval,errloc;
  int erasures;
  int decoder_errors = 0;
  void *rs;

  if(e->symsize > 8)
    return -1;

  /* Compute code parameters */
  kk = nn - e->nroots;

  rs = init_rs_char(e->symsize,e->genpoly,e->fcs,e->prim,e->nroots,0);
  if(rs == NULL){
    printf("init_rs_char failed!\n");
    return -1;
  }
  /* Test up to the error correction capacity of the code */
  for(errors=0;errors <= e->nroots/2;errors++){

    /* Load block with random data and encode */
    for(i=0;i<kk;i++)
      block[i] = random() & nn;
    memcpy(tblock,block,sizeof(block));
    encode_rs_char(rs,block,&block[kk]);

    /* Make temp copy, seed with errors */
    memcpy(tblock,block,sizeof(block));
    memset(errlocs,0,sizeof(errlocs));
    memset(derrlocs,0,sizeof(derrlocs));
    erasures=0;
    for(i=0;i<errors;i++){
      do {
	errval = random() & nn;
      } while(errval == 0); /* Error value must be nonzero */
      
      do {
	errloc = random() % nn;
      } while(errlocs[errloc] != 0); /* Must not choose the same location twice */
      
      errlocs[errloc] = 1;

#if FLAG_ERASURE
      if(random() & 1) /* 50-50 chance */
	derrlocs[erasures++] = errloc;
#endif
      tblock[errloc] ^= errval;
    }

    /* Decode the errored block */
    derrors = decode_rs_char(rs,tblock,derrlocs,erasures);

    if(derrors != errors){
	printf("(%d,%d) decoder says %d errors, true number is %d\n",nn,kk,derrors,errors);
	decoder_errors++;
    }
    for(i=0;i<derrors;i++){
      if(errlocs[derrlocs[i]] == 0){
	printf("(%d,%d) decoder indicates error in location %d without error\n",nn,kk,derrlocs[i]);
	decoder_errors++;
      }
    }
    if(memcmp(tblock,block,sizeof(tblock)) != 0){
      printf("(%d,%d) decoder uncorrected errors! output ^ input:",nn,kk);
      decoder_errors++;
      for(i=0;i<nn;i++)
	printf(" %02x",tblock[i] ^ block[i]);
      printf("\n");
    }
  }

  free_rs_char(rs);
  return 0;
}

int exercise_int(struct etab *e){
  int nn = (1<<e->symsize) - 1;
  int block[nn],tblock[nn];
  int errlocs[nn],derrlocs[nn];
  int i;
  int errors;
  int derrors,kk;
  int errval,errloc;
  int erasures;
  int decoder_errors = 0;
  void *rs;

  /* Compute code parameters */
  kk = nn - e->nroots;

  rs = init_rs_int(e->symsize,e->genpoly,e->fcs,e->prim,e->nroots,0);
  if(rs == NULL){
    printf("init_rs_int failed!\n");
    return -1;
  }
  /* Test up to the error correction capacity of the code */
  for(errors=0;errors <= e->nroots/2;errors++){

    /* Load block with random data and encode */
    for(i=0;i<kk;i++)
      block[i] = random() & nn;
    memcpy(tblock,block,sizeof(block));
    encode_rs_int(rs,block,&block[kk]);

    /* Make temp copy, seed with errors */
    memcpy(tblock,block,sizeof(block));
    memset(errlocs,0,sizeof(errlocs));
    memset(derrlocs,0,sizeof(derrlocs));
    erasures=0;
    for(i=0;i<errors;i++){
      do {
	errval = random() & nn;
      } while(errval == 0); /* Error value must be nonzero */
      
      do {
	errloc = random() % nn;
      } while(errlocs[errloc] != 0); /* Must not choose the same location twice */
      
      errlocs[errloc] = 1;

#if FLAG_ERASURE
      if(random() & 1) /* 50-50 chance */
	derrlocs[erasures++] = errloc;
#endif
      tblock[errloc] ^= errval;
    }

    /* Decode the errored block */
    derrors = decode_rs_int(rs,tblock,derrlocs,erasures);

    if(derrors != errors){
	printf("(%d,%d) decoder says %d errors, true number is %d\n",nn,kk,derrors,errors);
	decoder_errors++;
    }
    for(i=0;i<derrors;i++){
      if(errlocs[derrlocs[i]] == 0){
	printf("(%d,%d) decoder indicates error in location %d without error\n",nn,kk,derrlocs[i]);
	decoder_errors++;
      }
    }
    if(memcmp(tblock,block,sizeof(tblock)) != 0){
      printf("(%d,%d) decoder uncorrected errors! output ^ input:",nn,kk);
      decoder_errors++;
      for(i=0;i<nn;i++)
	printf(" %02x",tblock[i] ^ block[i]);
      printf("\n");
    }
  }

  free_rs_int(rs);
  return 0;
}