gistfile1.c

void oct2bin(const char *oct, int n, int nbit, char *bin, int skipLast, int flip)
{
    int i, cnt = 0, skip = 0;
    const static char octlist[8][3]={{1,1,1},{1,1,-1},{1,-1,1},{1,-1,-1},{-1,1,1},{-1,1,-1},{-1,-1,1},{-1,-1,-1}}; /* 0=>1, 1=>-1 */
 
    if(n * 3 >= nbit)
        skip = skipLast ? nbit : (n * 3 - nbit);
 
    for(i = 0; i < n * 3; ++i){
        if(skipLast){
            if(!(i < skip))
                continue;
        }else{
            if(!(i >= skip))
                continue;
        }
 
        bin[cnt] = octlist[oct[i / 3] - '0'][cnt % 3];
        ++cnt;
    }
 
    if(flip) fliparrayc(bin, nbit, bin);
}