BCH_32_21_5.rar_BCH 32_bch_bch 32_bch code_bch c语言

package com.zeph.j2se.bch; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Random; public class BCH_32_21_5 { private int m = 5, n = 31, k = 21, d = 5; private int length = 31; private int p[] = new int[6]; private int alpha_to[] = new int[32]; private int index_of[] = new int[32]; private int g[] = new int[11]; private int recd[] = new int[31]; private int data[] = new int[21]; private int bb[] = new int[11]; private int numerr, decerror = 0; private int errpos[] = new int[32]; private int seed; public void read_p() { p[0] = p[2] = p[5] = 1; p[1] = p[3] = p[4] = 0; } public void generate_gf() { int i, mask; mask = 1; alpha_to[m] = 0; for (i = 0; i < m; i++) { alpha_to[i] = mask; index_of[alpha_to[i]] = i; if (p[i] != 0) alpha_to[m] ^= mask; mask <<= 1; } index_of[alpha_to[m]] = m; mask >>= 1; for (i = m + 1; i < n; i++) { if (alpha_to[i - 1] >= mask) alpha_to[i] = alpha_to[m] ^ ((alpha_to[i - 1] ^ mask) << 1); else alpha_to[i] = alpha_to[i - 1] << 1; index_of[alpha_to[i]] = i; } index_of[0] = -1; } public void gen_poly() { int ii, jj, ll, kaux; int test, aux, nocycles, root, noterms, rdncy; int cycle[][] = new int[15][6]; int size[] = new int[15]; int min[] = new int[11]; int zeros[] = new int[11]; cycle[0][0] = 0; size[0] = 1; cycle[1][0] = 1; size[1] = 1; jj = 1; do { ii = 0; do { ii++; cycle[jj][ii] = (cycle[jj][ii - 1] * 2) % n; size[jj]++; aux = (cycle[jj][ii] * 2) % n; } while (aux != cycle[jj][0]); ll = 0; do { ll++; test = 0; // (!test) for (ii = 1; ((ii <= jj) && (test == 0)); ii++) // (!test) for (kaux = 0; ((kaux < size[ii]) && (test == 0)); kaux++) if (ll == cycle[ii][kaux]) test = 1; } while ((test != 0) && (ll < (n - 1)));// test if (test == 0) {// (!test) jj++; /* next cycle set index */ cycle[jj][0] = ll; size[jj] = 1; } } while (ll < (n - 1)); nocycles = jj; /* number of cycle sets modulo n */ kaux = 0; rdncy = 0; for (ii = 1; ii <= nocycles; ii++) { min[kaux] = 0; for (jj = 0; jj < size[ii]; jj++) for (root = 1; root < d; root++) if (root == cycle[ii][jj]) min[kaux] = ii; if (min[kaux] != 0) { rdncy += size[min[kaux]]; kaux++; } } noterms = kaux; kaux = 1; for (ii = 0; ii < noterms; ii++) for (jj = 0; jj < size[min[ii]]; jj++) { zeros[kaux] = cycle[min[ii]][jj]; kaux++; } System.out.printf("This is a (%d, %d, %d) binary BCH code\n", length, k, d); g[0] = alpha_to[zeros[1]]; g[1] = 1; /* g(x) = (X + zeros[1]) initially */ for (ii = 2; ii <= rdncy; ii++) { g[ii] = 1; for (jj = ii - 1; jj > 0; jj--) if (g[jj] != 0) g[jj] = g[jj - 1] ^ alpha_to[(index_of[g[jj]] + zeros[ii]) % n]; else g[jj] = g[jj - 1]; g[0] = alpha_to[(index_of[g[0]] + zeros[ii]) % n]; } System.out.printf("g(x) = "); for (ii = 0; ii <= rdncy; ii++) { System.out.printf("%d", g[ii]); if ((ii != 0) && ((ii % 70) == 0)) System.out.printf("\n"); } System.out.printf("\n"); } public void encode_bch() { int i, j; int feedback; for (i = 0; i < length - k; i++) bb[i] = 0; for (i = k - 1; i >= 0; i--) { feedback = data[i] ^ bb[length - k - 1]; if (feedback != 0) { for (j = length - k - 1; j > 0; j--) if (g[j] != 0) bb[j] = bb[j - 1] ^ feedback; else bb[j] = bb[j - 1]; bb[0] = g[0] & feedback;// g[0] && feedback } else { for (j = length - k - 1; j > 0; j--) bb[j] = bb[j - 1]; bb[0] = 0; } } } public void decode_bch() { int i, j, q; int elp[] = new int[3], s[] = new int[5], s3; int count = 0, syn_error = 0; int loc[] = new int[3], reg[] = new int[3]; int aux; /* first form the syndromes */ System.out.printf("s[] = ("); for (i = 1; i <= 4; i++) { s[i] = 0; for (j = 0; j < length; j++) if (recd[j] != 0) s[i] ^= alpha_to[(i * j) % n]; if (s[i] != 0) syn_error = 1; /* set flag if non-zero syndrome */ /* * NOTE: If only error detection is needed, then exit the program * here... */ /* convert syndrome from polynomial form to index form */ s[i] = index_of[s[i]]; System.out.printf("%3d ", s[i]); } System.out.printf(")\n"); if (syn_error != 0) { /* If there are errors, try to correct them */ if (s[1] != -1) { s3 = (s[1] * 3) % n; if (s[3] == s3) /* Was it a single error ? */ { System.out.printf("One error at %d\n", s[1]); recd[s[1]] ^= 1; /* Yes: Correct it */ } else { /* * Assume two errors occurred and solve for the * coefficients of sigma(x), the error locator * polynomail */ if (s[3] != -1) aux = alpha_to[s3] ^ alpha_to[s[3]]; else aux = alpha_to[s3]; elp[0] = 0; elp[1] = (s[2] - index_of[aux] + n) % n; elp[2] = (s[1] - index_of[aux] + n) % n; System.out.printf("sigma(x) = "); for (i = 0; i <= 2; i++) System.out.printf("%3d ", elp[i]); System.out.printf("\n"); System.out.printf("Roots: "); /* find roots of the error location polynomial */ for (i = 1; i <= 2; i++) reg[i] = elp[i]; count = 0; for (i = 1; i <= n; i++) { /* Chien search */ q = 1; for (j = 1; j <= 2; j++) if (reg[j] != -1) { reg[j] = (reg[j] + j) % n; q ^= alpha_to[reg[j]]; } if (q == 0) { /* store error location number indices */ loc[count] = i % n; count++; System.out.printf("%3d ", (i % n)); } } System.out.printf("\n"); if (count == 2) /* no. roots = degree of elp hence 2 errors */ for (i = 0; i < 2; i++) recd[loc[i]] ^= 1; else /* Cannot solve: Error detection */ System.out.printf("incomplete decoding\n"); } } else if (s[2] != -1) /* Error detection */ System.out.printf("incomplete decoding\n"); } } public void run() { int i; read_p(); /* read generator polynomial g(x) */ generate_gf(); /* generate the Galois Field GF(2**m) */ gen_poly(); /* Compute the generator polynomial of BCH code */ seed = 1; Random random = new Random(seed); /* Randomly generate DATA */ for (i = 0; i < k; i++) data[i] = (random.nextInt() & 67108864) >> 26; /* ENCODE */ encode_bch(); /* encode data */ for (i = 0; i < length - k; i++) recd[i] = bb[i]; /* first (length-k) bits are redundancy */ for (i = 0; i < k; i++) recd[i + length - k] = data[i]; /* last k bits are data */ System.out.printf("c(x) = "); for (i = 0; i < length; i++) { System.out.printf("%1d", recd[i]); if ((i != 0) && ((i % 70) == 0)) System.out.printf("\n"); } System.out.printf("\n"); /* ERRORS */ System.out.printf("Enter the number of errors and their positions: "); BufferedReader wt = new BufferedReader(new InputStreamReader(System.in)); String numerrStr = null; try { numerrStr = wt.readLine(); } catch (IOException e) { e.printStackTrace(); } numerr = Integer.valueOf(numerrStr); for (i = 0; i < numerr; i++) { String errposStr = null; try { errposStr = wt.readLine(); } catch (IOException e) { e.printStackTrace(); } errpos[i] = Integer.valueOf(errposStr); recd[errpos[i]] ^= 1; } System.out.printf("r(x) = "); for (i = 0; i < length; i++) System.out.printf("%1d", recd[i]); System.out.printf("\n"); /* DECODE */ decode_bch(); /* * print out original and decoded data */ System.out.printf("Results:\n"); System.out.printf("original data = "); for (i = 0; i < k; i++)