Class BitSet

classpath/java/util/BitSet.java:19–267

@author zsombor

 * 
 */
public class BitSet implements Serializable, Cloneable {

  final static int  BITS_PER_LONG       = 64;
  final static int  BITS_PER_LONG_SHIFT = 6;
  final static long MASK                = 0xFFFFFFFFFFFFFFFFL;

  private long[]    bits;

  private static int longPosition(int index) {
    return index >> BITS_PER_LONG_SHIFT;
  }

  private static long bitPosition(int index) {
    return 1L << (index % BITS_PER_LONG);
  }

  private static long getTrueMask(int fromIndex, int toIndex) {
    int currentRange = toIndex - fromIndex;
    return (MASK >>> (BITS_PER_LONG - currentRange)) << (fromIndex % BITS_PER_LONG);
  }

  public BitSet(int bitLength) {
    if (bitLength % BITS_PER_LONG == 0) {
      enlarge(longPosition(bitLength));
    } else {
      enlarge(longPosition(bitLength) + 1);
    }
  }

  public BitSet() {
    enlarge(1);
  }

  public void and(BitSet otherBits) {
    int min = Math.min(bits.length, otherBits.bits.length);
    for (int i = 0; i < min; i++) {
      bits[i] &= otherBits.bits[i];
    }
    for (int i = min; i < bits.length; i++) { 
      bits[i] = 0;
    }
  }

  public void andNot(BitSet otherBits) {
    int max = Math.max(bits.length, otherBits.bits.length);
    enlarge(max);
    int min = Math.min(bits.length, otherBits.bits.length);
    for (int i = 0; i < min; i++) {
      bits[i] &= ~otherBits.bits[i];
    }
  }

  public void or(BitSet otherBits) {
    int max = Math.max(bits.length, otherBits.bits.length);
    enlarge(max);
    int min = Math.min(bits.length, otherBits.bits.length);
    for (int i = 0; i < min; i++) {
      bits[i] |= otherBits.bits[i];