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package com.oracle.truffle.regex.util;

import java.util.PrimitiveIterator;

public final class Abstract64BitSet {

    private static long toBit(int b) {
        return 1L << b;
    }

    public static boolean isEmpty(long bs) {
        return bs == 0;
    }

    public static boolean isFull(long bs) {
        return bs == ~0L;
    }

    public static int size(long bs) {
        return Long.bitCount(bs);
    }

    public static boolean get(long bs, int b) {
        return b < 64 && (bs & toBit(b)) != 0;
    }

    public static long set(long bs, int b) {
        assert b < 64;
        return bs | toBit(b);
    }

    public static long clear(long bs, int b) {
        assert b < 64;
        return bs & ~toBit(b);
    }

    public static boolean intersects(long bs1, long bs2) {
        return !isDisjoint(bs1, bs2);
    }

    public static boolean isDisjoint(long bs1, long bs2) {
        return (bs1 & bs2) == 0;
    }

    public static boolean contains(long bs1, long bs2) {
        return (bs1 & bs2) == bs2;
    }

    /**
     * Compatible with {@link BitSets#hashCode(long[])}.
     */
    public static int hashCode(long bs) {
        long h = 1234 ^ bs;
        return (int) ((h >> 32) ^ h);
    }

    public static boolean equals(long bs1, long bs2) {
        return bs1 == bs2;
    }

    public static PrimitiveIterator.OfInt iterator(long bs) {
        return new Abstract64BitSetIterator(bs);
    }

    private static final class Abstract64BitSetIterator implements PrimitiveIterator.OfInt {

        private long bs;
        private int i = -1;

        Abstract64BitSetIterator(long bs) {
            this.bs = bs;
        }

        @Override
        public boolean hasNext() {
            return bs != 0;
        }

        @Override
        public int nextInt() {
            assert hasNext();
            int trailingZeros = Long.numberOfTrailingZeros(bs);
            bs >>>= trailingZeros;
            bs >>>= 1;
            i += trailingZeros + 1;
            return i;
        }
    }
}