libjava/java/util/BitSet.java

// BitSet - A vector of bits.

/* Copyright (C) 1998, 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

package java.util;
import java.io.Serializable;

/**
 * @author Tom Tromey <tromey@cygnus.com>
 * @date October 23, 1998.
 */

/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
 * hashCode algorithm taken from JDK 1.2 docs.
 */

public final class BitSet implements Cloneable, Serializable
{
  public void and (BitSet bs)
    {
      if (bs == null)
	throw new NullPointerException ();
      int max = Math.min(bits.length, bs.bits.length);
      int i;
      for (i = 0; i < max; ++i)
	bits[i] &= bs.bits[i];
      for ( ; i < bits.length; ++i)
	bits[i] = 0;
    }

  public BitSet ()
    {
      this (64);
    }

  public BitSet (int nbits)
    {
      if (nbits < 0)
	throw new NegativeArraySizeException ();
      int length = nbits / 64;
      if (nbits % 64 != 0)
	++length;
      bits = new long[length];
    }

  public void clear (int pos)
    {
      if (pos < 0)
	throw new IndexOutOfBoundsException ();
      int bit = pos % 64;
      int offset = pos / 64;
      ensure (offset);
      bits[offset] &= ~ (1 << bit);
    }

  public Object clone ()
    {
      BitSet bs = new BitSet (bits.length * 64);
      System.arraycopy(bits, 0, bs.bits, 0, bits.length);
      return bs;
    }

  public boolean equals (Object obj)
    {
      if (! (obj instanceof BitSet))
	return false;
      BitSet bs = (BitSet) obj;
      int max = Math.min(bits.length, bs.bits.length);
      int i;
      for (i = 0; i < max; ++i)
	if (bits[i] != bs.bits[i])
	  return false;
      // If one is larger, check to make sure all extra bits are 0.
      for (int j = i; j < bits.length; ++j)
	if (bits[j] != 0)
	  return false;
      for (int j = i; j < bs.bits.length; ++j)
	if (bs.bits[j] != 0)
	  return false;
      return true;
    }

  public boolean get (int pos)
    {
      if (pos < 0)
	throw new IndexOutOfBoundsException ();

      int bit = pos % 64;
      int offset = pos / 64;

      if (offset >= bits.length)
	return false;

      return (bits[offset] & (1 << bit)) == 0 ? false : true;
    }

  public int hashCode ()
    {
      long h = 1234;
      for (int i = bits.length - 1; i >= 0; --i)
	h ^= bits[i] * (i + 1);
      return (int) ((h >> 32) ^ h);
    }

  public void or (BitSet bs)
    {
      if (bs == null)
	throw new NullPointerException ();
      ensure (bs.bits.length - 1);
      int i;
      for (i = 0; i < bs.bits.length; ++i)
	bits[i] |= bs.bits[i];
    }

  public void set (int pos)
    {
      if (pos < 0)
	throw new IndexOutOfBoundsException ();
      int bit = pos % 64;
      int offset = pos / 64;
      ensure (offset);
      bits[offset] |= 1 << bit;
    }

  public int size ()
    {
      return bits.length * 64;
    }

  public String toString ()
    {
      StringBuffer result = new StringBuffer ("{");
      boolean first = true;
      for (int i = 0; i < bits.length; ++i)
	{
	  int bit = 1;
	  long word = bits[i];
	  for (int j = 0; j < 64; ++j)
	    {
	      if ((word & bit) != 0)
		{
		  if (! first)
		    result.append(", ");
		  result.append(64 * i + j);
		  first = false;
		}
	      bit <<= 1;
	    }
	}

      return result.append("}").toString();
    }

  public void xor (BitSet bs)
    {
      if (bs == null)
	throw new NullPointerException ();
      ensure (bs.bits.length - 1);
      int i;
      for (i = 0; i < bs.bits.length; ++i)
	bits[i] ^= bs.bits[i];
    }

  // Make sure the vector is big enough.
  private final void ensure (int lastElt)
    {
      if (lastElt + 1 > bits.length)
	{
	  long[] nd = new long[lastElt + 1];
	  System.arraycopy(bits, 0, nd, 0, bits.length);
	  bits = nd;
	}
    }

  // The actual bits.
  private long[] bits;
}