package java.util;

import java.io.Serializable;

/**
 * @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);
  }

  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 max = Math.max(bits.length, otherBits.bits.length);
    for (int i = 0; i < max; i++) {
      bits[i] &= otherBits.bits[i];
    }
  }

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

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

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

  private void enlarge(int newSize) {
    if (bits == null || bits.length <= newSize) {
      long[] newBits = new long[newSize + 1];
      if (bits != null) {
        System.arraycopy(bits, 0, newBits, 0, bits.length);
      }
      bits = newBits;
    }
  }

  public void clear(int index) {
    int pos = longPosition(index);
    if (pos < bits.length) {
      bits[pos] &= (MASK ^ bitPosition(index));
    }
  }

  public boolean get(int index) {
    int pos = longPosition(index);
    if (pos < bits.length) {
      return (bits[pos] & bitPosition(index)) != 0;
    }
    return false;
  }

  public void set(int index) {
    int pos = longPosition(index);
    enlarge(pos);
    bits[pos] |= bitPosition(index);
  }

  public void set(int start, int end) {
    for (int i = start; i < end; i++) {
      set(i);
    }
  }

  public void clear(int start, int end) {
    for (int i = start; i < end; i++) {
      clear(i);
    }
  }

  public boolean isEmpty() {
    for (int i = 0; i < bits.length; i++) {
      if (bits[i] != 0) {
        return false;
      }
    }
    return true;
  }

  public boolean intersects(BitSet otherBits) {
    int max = Math.max(bits.length, otherBits.bits.length);
    for (int i = 0; i < max; i++) {
      if ((bits[i] & otherBits.bits[i]) != 0) {
        return true;
      }
    }
    return false;
  }

  public int length() {
    return bits.length << BITS_PER_LONG_SHIFT;
  }

  public int nextSetBit(int fromIndex) {
    return nextBit(fromIndex, false);
  }

  private int nextBit(int fromIndex, boolean bitClear) {
    int pos = longPosition(fromIndex);
    if (pos >= bits.length) {
      return -1;
    }
    int current = fromIndex;
    do {
      long currValue = bits[pos];
      if (currValue == 0) {
        pos++;
        current = pos << BITS_PER_LONG_SHIFT;
      } else {
        do {
          long bitPos = bitPosition(current);
          if (((currValue & bitPos) != 0) ^ bitClear) {
            return current;
          } else {
            current++;
          }
        } while (current % BITS_PER_LONG != 0);
      }
      pos++;
    } while (pos < bits.length);

    return -1;
  }

  public int nextClearBit(int fromIndex) {
    return nextBit(fromIndex, true);
  }

}