bool BCH::decode(int &err_n, _64bits &orig_n, const int encoded_bits[BCH_DEFAULT_LENGTH])
{
assert(k == BCH_DEFAULT_K && length == BCH_DEFAULT_LENGTH);
int temp_bits[BCH_DEFAULT_LENGTH];
for(int i=0; i<BCH_DEFAULT_LENGTH; i++) temp_bits[i] = encoded_bits[i];
err_n = decode_bch(temp_bits);
if(err_n > t) return(false);
orig_n = fromBitPattern(&temp_bits[length - k],BCH_DEFAULT_K);
return(true);
}
main()
{
int i;
read_p(); /* Read m */
generate_gf(); /* Construct the Galois Field GF(2**m) */
gen_poly(); /* Compute the generator polynomial of BCH code */
/* Randomly generate DATA */
seed = 131073;
srandom(seed);
for (i = 0; i < k; i++)
data[i] = ( random() & 65536 ) >> 16;
encode_bch(); /* encode data */
/*
* recd[] are the coefficients of c(x) = x**(length-k)*data(x) + b(x)
*/
for (i = 0; i < length - k; i++)
recd[i] = bb[i];
for (i = 0; i < k; i++)
recd[i + length - k] = data[i];
printf("Code polynomial:\nc(x) = ");
for (i = 0; i < length; i++) {
printf("%1d", recd[i]);
if (i && ((i % 50) == 0))
printf("\n");
}
printf("\n");
printf("Enter the number of errors:\n");
scanf("%d", &numerr); /* CHANNEL errors */
printf("Enter error locations (integers between");
printf(" 0 and %d): ", length-1);
/*
* recd[] are the coefficients of r(x) = c(x) + e(x)
*/
for (i = 0; i < numerr; i++)
scanf("%d", &errpos[i]);
if (numerr)
for (i = 0; i < numerr; i++)
recd[errpos[i]] ^= 1;
printf("r(x) = ");
for (i = 0; i < length; i++) {
printf("%1d", recd[i]);
if (i && ((i % 50) == 0))
printf("\n");
}
printf("\n");
decode_bch(); /* DECODE received codeword recv[] */
/*
* print out original and decoded data
*/
printf("Results:\n");
printf("original data = ");
for (i = 0; i < k; i++) {
printf("%1d", data[i]);
if (i && ((i % 50) == 0))
printf("\n");
}
printf("\nrecovered data = ");
for (i = length - k; i < length; i++) {
printf("%1d", recd[i]);
if ((i-length+k) && (((i-length+k) % 50) == 0))
printf("\n");
}
printf("\n");
/*
* DECODING ERRORS? we compare only the data portion
*/
for (i = length - k; i < length; i++)
if (data[i - length + k] != recd[i])
decerror++;
if (decerror)
printf("There were %d decoding errors in message positions\n", decerror);
else
printf("Succesful decoding\n");
}
