getSpecialWord-additionTable.c

void getSpecialWord(uint16_t _n, char* buffer) {
    static uint16_t w;
    w = 0;
    const uint8_t* b = answers;
    static uint16_t n;
    n = _n + 1;
    static uint8_t additionTable[256];
    static uint8_t tableReady = 0;
    static uint8_t c;
    static uint8_t mask;
    
    if (!tableReady) {
        for (c=255;c;c--) {
            static uint8_t count;
            count = 0;
            for (mask = 1 ; mask ; mask <<= 1)
                if (c & mask)
                    count++;
            additionTable[c] = count;
        }
        additionTable[0] = 0;
        tableReady = 1;
    }

    for(;;) { 
        c = *b++;
        uint8_t delta = additionTable[c];
        if (n > delta) {
            n -= delta;
            w += 8;
        }
        else {
            for (mask = 1 ; mask ; mask <<= 1) {
                if (c & mask) {
                    n--;
                    if (n == 0) {
                        getWord(w, buffer);
                        return;
                    }
                }
                w++;
            }
        }
    }
}