number-theoretic/primes

import {itop2} from './itop2.js';
import {ptoi2} from './ptoi2.js';

/**
 * Sieve of Eratosthenes skipping all multiples of 2.
 */

export function __eratosthenes2__(alloc, fill, get, gothrough, usqrt) {
    const first = 3;

    const eratosthenes2 = function (n, callback) {
        if (n <= 2) {
            return null;
        }

        callback(2);

        if (n <= 3) {
            return null;
        }

        const size = ptoi2(n);

        const sieve = alloc(size);
        fill(sieve, 0, size, true);

        const m = ptoi2(usqrt(n));

        for (let i = ptoi2(first); i < m; ++i) {
            if (get(sieve, i)) {
                const p = itop2(i);
                callback(p);
                gothrough(sieve, ptoi2(p * p), size, p);
            }
        }

        for (let i = m; i < size; ++i) {
            if (get(sieve, i)) {
                callback(itop2(i));
            }
        }

        return sieve;
    };

    return eratosthenes2;
}