rstest.c

Reed-Solomn code 编译码(含CCSDS鞋译） 算法

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "rs.h"


void
fill_eras(int eras_pos[],int n)
{
  int i,j,t,work[NN];

  for(i=0;i<NN;i++)
    work[i] = i;
  for(j=NN-1;j>0;j--){
    i = random() % j;	/* not really uniform, I know */
    t = work[i];
    work[i] = work[j];
    work[j] = t;
  }
#ifdef notdef
  for(i=0;i<NN;i++)
    printf(" %d",work[i]);
  printf("\n");
#endif
  for(i=0;i<n;i++)
    eras_pos[i] = work[i];
}

/* Return non-zero random number in range 0 - NN (NN power of 2 minus 1) */
int
randomnz(void)
{
  int i;
  
  while((i = random() & NN) == 0)
    ;
  return i;
}

int
main(int argc,char *argv[])
{

  dtype data[NN];
  dtype tdata[NN];
  dtype ddata[NN];
  int eras_pos[NN];
  int i,trials,k;
  long t;
  int nerrors,nerase,ntrials,verbose,timetest;
  int detfails,fails;
  extern char *optarg;
  
  nerrors = nerase = 0;
  timetest = verbose = 0;
  ntrials = 100;
  while((i = getopt(argc,argv,"e:E:n:vt")) != EOF){
    switch(i){
    case 'e':	/* Number of errors per block */
      nerrors = atoi(optarg);
      break;
    case 'E':	/* Number of erasures per block */
      nerase = atoi(optarg);
      break;
    case 'n':	/* Number of trials */
      ntrials = atoi(optarg);
      break;
    case 'v':	/* Be verbose */
      verbose = 1;
      break;
    case 't':	/* Repeatedly decode the same block */
      timetest = 1;
      break;
    default:
      printf("usage: %s [-v] [-t] [-e errors] [-E erasures] [-n ntrials]\n",argv[0]);
      exit(1);
    }
  }
  printf("Reed-Solomon code is (%d,%d) over GF(%d)\n",
	 NN,KK,NN+1);
  printf("test erasures: %d errors %d\n",nerase,nerrors);
  if(2*nerrors + nerase > NN-KK)
    printf("Warning: %d errors and %d erasures exceeds the correction ability of the code\n",nerrors,nerase);
  time(&t);
  srandom(t);
  
  if(timetest){
    printf("Speed timing test (repeated decoding of same block)\n");
    for(i=0;i<KK;i++)
      data[i] = random() & NN;
    encode_rs(data,&data[KK]);
    fill_eras(eras_pos,nerase+nerrors);
    if(verbose && nerase){
      printf("erasing:");
      for(i=0;i<nerase;i++)
	printf(" %d",eras_pos[i]);
      printf("\n");
    }
    if(verbose && nerrors){
      printf("erroring:");
      for(i=nerase;i<nerase+nerrors;i++)
	printf(" %d",eras_pos[i]);
      printf("\n");
    }
    memcpy(tdata,data,sizeof(data));
    for(i=0;i<nerase+nerrors;i++)
      tdata[eras_pos[i]] ^= randomnz();
    
    for(k=0;k<ntrials;k++){
      memcpy(ddata,tdata,sizeof(tdata));
      eras_dec_rs(ddata,eras_pos,nerase);
    }
    exit(0);
  }
  fails = detfails = 0;
  for(trials=0;trials < ntrials;trials++){
    if(verbose)
      printf("Trial %d:",trials);
    for(i=0;i<KK;i++)
      data[i] = random() & NN;
    encode_rs(data,&data[KK]);
    fill_eras(eras_pos,nerase+nerrors);
    if(verbose && nerase){
      printf(" erasing:");
      for(i=0;i<nerase;i++)
	printf(" %d",eras_pos[i]);
    }
    if(verbose && nerrors){
      printf(" erroring:");
      for(i=nerase;i<nerase+nerrors;i++)
	printf(" %d",eras_pos[i]);
    }
    if(verbose)
      printf("\n");
    memcpy(ddata,data,sizeof(data));
    for(i=0;i<nerase+nerrors;i++)
      ddata[eras_pos[i]] ^= randomnz();
    
    i = eras_dec_rs(ddata,eras_pos,nerase);
    if(verbose){
      printf("errs + erasures corrected: %d\n",i);
    }
    if(i == -1){
      detfails++;
      printf("RS decoder detected failure\n");
    } else if(memcmp(ddata,data,NN) != 0){
      fails++;
      printf("Undetected decoding failure!\n");
    }
  }
  printf("Trials: %d decoding failures: %d; not detected by decoder: %d\n",
	 ntrials,detfails,fails);
  return 0;
}