openbitset.java

lucene-2.4.0 是一个全文收索的工具包

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.util;

import java.util.Arrays;
import java.io.Serializable;

import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.DocIdSetIterator;

/** An "open" BitSet implementation that allows direct access to the array of words
 * storing the bits.
 * <p/>
 * Unlike java.util.bitset, the fact that bits are packed into an array of longs
 * is part of the interface.  This allows efficient implementation of other algorithms
 * by someone other than the author.  It also allows one to efficiently implement
 * alternate serialization or interchange formats.
 * <p/>
 * <code>OpenBitSet</code> is faster than <code>java.util.BitSet</code> in most operations
 * and *much* faster at calculating cardinality of sets and results of set operations.
 * It can also handle sets of larger cardinality (up to 64 * 2**32-1)
 * <p/>
 * The goals of <code>OpenBitSet</code> are the fastest implementation possible, and
 * maximum code reuse.  Extra safety and encapsulation
 * may always be built on top, but if that's built in, the cost can never be removed (and
 * hence people re-implement their own version in order to get better performance).
 * If you want a "safe", totally encapsulated (and slower and limited) BitSet
 * class, use <code>java.util.BitSet</code>.
 * <p/>
 * <h3>Performance Results</h3>
 *
 Test system: Pentium 4, Sun Java 1.5_06 -server -Xbatch -Xmx64M
<br/>BitSet size = 1,000,000
<br/>Results are java.util.BitSet time divided by OpenBitSet time.
<table border="1">
 <tr>
  <th></th> <th>cardinality</th> <th>intersect_count</th> <th>union</th> <th>nextSetBit</th> <th>get</th> <th>iterator</th>
 </tr>
 <tr>
  <th>50% full</th> <td>3.36</td> <td>3.96</td> <td>1.44</td> <td>1.46</td> <td>1.99</td> <td>1.58</td>
 </tr>
 <tr>
   <th>1% full</th> <td>3.31</td> <td>3.90</td> <td>&nbsp;</td> <td>1.04</td> <td>&nbsp;</td> <td>0.99</td>
 </tr>
</table>
<br/>
Test system: AMD Opteron, 64 bit linux, Sun Java 1.5_06 -server -Xbatch -Xmx64M
<br/>BitSet size = 1,000,000
<br/>Results are java.util.BitSet time divided by OpenBitSet time.
<table border="1">
 <tr>
  <th></th> <th>cardinality</th> <th>intersect_count</th> <th>union</th> <th>nextSetBit</th> <th>get</th> <th>iterator</th>
 </tr>
 <tr>
  <th>50% full</th> <td>2.50</td> <td>3.50</td> <td>1.00</td> <td>1.03</td> <td>1.12</td> <td>1.25</td>
 </tr>
 <tr>
   <th>1% full</th> <td>2.51</td> <td>3.49</td> <td>&nbsp;</td> <td>1.00</td> <td>&nbsp;</td> <td>1.02</td>
 </tr>
</table>

 * @version $Id$
 */

public class OpenBitSet extends DocIdSet implements Cloneable, Serializable {
  protected long[] bits;
  protected int wlen;   // number of words (elements) used in the array

  /** Constructs an OpenBitSet large enough to hold numBits.
   *
   * @param numBits
   */
  public OpenBitSet(long numBits) {
    bits = new long[bits2words(numBits)];
    wlen = bits.length;
  }

  public OpenBitSet() {
    this(64);
  }

  /** Constructs an OpenBitSet from an existing long[].
   * <br/>
   * The first 64 bits are in long[0],
   * with bit index 0 at the least significant bit, and bit index 63 at the most significant.
   * Given a bit index,
   * the word containing it is long[index/64], and it is at bit number index%64 within that word.
   * <p>
   * numWords are the number of elements in the array that contain
   * set bits (non-zero longs).
   * numWords should be &lt= bits.length, and
   * any existing words in the array at position &gt= numWords should be zero.
   *
   */
  public OpenBitSet(long[] bits, int numWords) {
    this.bits = bits;
    this.wlen = numWords;
  }
  
  public DocIdSetIterator iterator() {
    return new OpenBitSetIterator(bits, wlen);
  }

  /** Returns the current capacity in bits (1 greater than the index of the last bit) */
  public long capacity() { return bits.length << 6; }

 /**
  * Returns the current capacity of this set.  Included for
  * compatibility.  This is *not* equal to {@link #cardinality}
  */
  public long size() {
      return capacity();
  }

  /** Returns true if there are no set bits */
  public boolean isEmpty() { return cardinality()==0; }

  /** Expert: returns the long[] storing the bits */
  public long[] getBits() { return bits; }

  /** Expert: sets a new long[] to use as the bit storage */
  public void setBits(long[] bits) { this.bits = bits; }

  /** Expert: gets the number of longs in the array that are in use */
  public int getNumWords() { return wlen; }

  /** Expert: sets the number of longs in the array that are in use */
  public void setNumWords(int nWords) { this.wlen=nWords; }



  /** Returns true or false for the specified bit index. */
  public boolean get(int index) {
    int i = index >> 6;               // div 64
    // signed shift will keep a negative index and force an
    // array-index-out-of-bounds-exception, removing the need for an explicit check.
    if (i>=bits.length) return false;

    int bit = index & 0x3f;           // mod 64
    long bitmask = 1L << bit;
    return (bits[i] & bitmask) != 0;
  }


 /** Returns true or false for the specified bit index.
   * The index should be less than the OpenBitSet size
   */
  public boolean fastGet(int index) {
    int i = index >> 6;               // div 64
    // signed shift will keep a negative index and force an
    // array-index-out-of-bounds-exception, removing the need for an explicit check.
    int bit = index & 0x3f;           // mod 64
    long bitmask = 1L << bit;
    return (bits[i] & bitmask) != 0;
  }



 /** Returns true or false for the specified bit index
  */
  public boolean get(long index) {
    int i = (int)(index >> 6);             // div 64
    if (i>=bits.length) return false;
    int bit = (int)index & 0x3f;           // mod 64
    long bitmask = 1L << bit;
    return (bits[i] & bitmask) != 0;
  }

  /** Returns true or false for the specified bit index.
   * The index should be less than the OpenBitSet size.
   */
  public boolean fastGet(long index) {
    int i = (int)(index >> 6);               // div 64
    int bit = (int)index & 0x3f;           // mod 64
    long bitmask = 1L << bit;
    return (bits[i] & bitmask) != 0;
  }

  /*
  // alternate implementation of get()
  public boolean get1(int index) {
    int i = index >> 6;                // div 64
    int bit = index & 0x3f;            // mod 64
    return ((bits[i]>>>bit) & 0x01) != 0;
    // this does a long shift and a bittest (on x86) vs
    // a long shift, and a long AND, (the test for zero is prob a no-op)
    // testing on a P4 indicates this is slower than (bits[i] & bitmask) != 0;
  }
  */


  /** returns 1 if the bit is set, 0 if not.
   * The index should be less than the OpenBitSet size
   */
  public int getBit(int index) {
    int i = index >> 6;                // div 64
    int bit = index & 0x3f;            // mod 64
    return ((int)(bits[i]>>>bit)) & 0x01;
  }


  /*
  public boolean get2(int index) {
    int word = index >> 6;            // div 64
    int bit = index & 0x0000003f;     // mod 64
    return (bits[word] << bit) < 0;   // hmmm, this would work if bit order were reversed
    // we could right shift and check for parity bit, if it was available to us.
  }
  */

  /** sets a bit, expanding the set size if necessary */
  public void set(long index) {
    int wordNum = expandingWordNum(index);
    int bit = (int)index & 0x3f;
    long bitmask = 1L << bit;
    bits[wordNum] |= bitmask;
  }


 /** Sets the bit at the specified index.
  * The index should be less than the OpenBitSet size.
  */
  public void fastSet(int index) {
    int wordNum = index >> 6;      // div 64
    int bit = index & 0x3f;     // mod 64
    long bitmask = 1L << bit;
    bits[wordNum] |= bitmask;
  }

 /** Sets the bit at the specified index.
  * The index should be less than the OpenBitSet size.
  */
  public void fastSet(long index) {
    int wordNum = (int)(index >> 6);
    int bit = (int)index & 0x3f;
    long bitmask = 1L << bit;
    bits[wordNum] |= bitmask;
  }

  /** Sets a range of bits, expanding the set size if necessary
   *
   * @param startIndex lower index
   * @param endIndex one-past the last bit to set
   */
  public void set(long startIndex, long endIndex) {
    if (endIndex <= startIndex) return;

    int startWord = (int)(startIndex>>6);

    // since endIndex is one past the end, this is index of the last
    // word to be changed.
    int endWord   = expandingWordNum(endIndex-1);

    long startmask = -1L << startIndex;
    long endmask = -1L >>> -endIndex;  // 64-(endIndex&0x3f) is the same as -endIndex due to wrap

    if (startWord == endWord) {
      bits[startWord] |= (startmask & endmask);
      return;
    }

    bits[startWord] |= startmask;
    Arrays.fill(bits, startWord+1, endWord, -1L);
    bits[endWord] |= endmask;
  }



  protected int expandingWordNum(long index) {
    int wordNum = (int)(index >> 6);
    if (wordNum>=wlen) {
      ensureCapacity(index+1);
      wlen = wordNum+1;
    }
    return wordNum;
  }


  /** clears a bit.
   * The index should be less than the OpenBitSet size.
   */
  public void fastClear(int index) {
    int wordNum = index >> 6;
    int bit = index & 0x03f;
    long bitmask = 1L << bit;
    bits[wordNum] &= ~bitmask;
    // hmmm, it takes one more instruction to clear than it does to set... any
    // way to work around this?  If there were only 63 bits per word, we could
    // use a right shift of 10111111...111 in binary to position the 0 in the
    // correct place (using sign extension).
    // Could also use Long.rotateRight() or rotateLeft() *if* they were converted
    // by the JVM into a native instruction.
    // bits[word] &= Long.rotateLeft(0xfffffffe,bit);
  }

  /** clears a bit.
   * The index should be less than the OpenBitSet size.
   */
  public void fastClear(long index) {
    int wordNum = (int)(index >> 6); // div 64
    int bit = (int)index & 0x3f;     // mod 64
    long bitmask = 1L << bit;
    bits[wordNum] &= ~bitmask;
  }

  /** clears a bit, allowing access beyond the current set size without changing the size.*/
  public void clear(long index) {
    int wordNum = (int)(index >> 6); // div 64
    if (wordNum>=wlen) return;
    int bit = (int)index & 0x3f;     // mod 64
    long bitmask = 1L << bit;
    bits[wordNum] &= ~bitmask;
  }

  /** Clears a range of bits.  Clearing past the end does not change the size of the set.
   *
   * @param startIndex lower index
   * @param endIndex one-past the last bit to clear
   */
  public void clear(long startIndex, long endIndex) {
    if (endIndex <= startIndex) return;

    int startWord = (int)(startIndex>>6);
    if (startWord >= wlen) return;

    // since endIndex is one past the end, this is index of the last
    // word to be changed.
    int endWord   = (int)((endIndex-1)>>6);

    long startmask = -1L << startIndex;
    long endmask = -1L >>> -endIndex;  // 64-(endIndex&0x3f) is the same as -endIndex due to wrap

    // invert masks since we are clearing
    startmask = ~startmask;
    endmask = ~endmask;

    if (startWord == endWord) {
      bits[startWord] &= (startmask | endmask);
      return;
    }

    bits[startWord] &= startmask;

    int middle = Math.min(wlen, endWord);
    Arrays.fill(bits, startWord+1, middle, 0L);
    if (endWord < wlen) {
      bits[endWord] &= endmask;
    }
  }



  /** Sets a bit and returns the previous value.
   * The index should be less than the OpenBitSet size.
   */
  public boolean getAndSet(int index) {
    int wordNum = index >> 6;      // div 64
    int bit = index & 0x3f;     // mod 64
    long bitmask = 1L << bit;
    boolean val = (bits[wordNum] & bitmask) != 0;
    bits[wordNum] |= bitmask;
    return val;
  }

  /** Sets a bit and returns the previous value.
   * The index should be less than the OpenBitSet size.
   */
  public boolean getAndSet(long index) {
    int wordNum = (int)(index >> 6);      // div 64
    int bit = (int)index & 0x3f;     // mod 64
    long bitmask = 1L << bit;
    boolean val = (bits[wordNum] & bitmask) != 0;