for (i = 1; i <= t2; i++) {
s[i] = 0;
for (j = 0; j < length; j++)
if (cx[j] != 0)
s[i] ^= alpha_to[(i * j) % n];
if (s[i] != 0)
syn_error = 1;
s[i] = index_of[s[i]];
//printf("%3d ", s[i]);
}
得到s alpha和index是形参 t2大概在6000，length大概在16383，n和length相等