content: /**
   * 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.io.IOException;
  import java.util.Arrays;
  
  import org.apache.lucene.search.DocIdSet;
  import org.apache.lucene.search.DocIdSetIterator;
  
  // TODO: maybe merge with BitVector?  Problem is BitVector
  // caches its cardinality...
  
  /** BitSet of fixed length (numBits), backed by accessible
   *  ({@link #getBits}) long[], accessed with an int index,
   *  implementing Bits and DocIdSet.  Unlike {@link
   *  OpenBitSet} this bit set does not auto-expand, cannot
   *  handle long index, and does not have fastXX/XX variants
   *  (just X).
   *
   * @lucene.internal
   **/
  
  public final class FixedBitSet extends DocIdSet implements Bits {
    private final long[] bits;
    private int numBits;
  
    /** returns the number of 64 bit words it would take to hold numBits */
    public static int bits2words(int numBits) {
      int numLong = numBits >>> 6;
      if ((numBits & 63) != 0) {
        numLong++;
      }
      return numLong;
    }
  
    public FixedBitSet(int numBits) {
      this.numBits = numBits;
      bits = new long[bits2words(numBits)];
    }
  
    /** Makes full copy. */
    public FixedBitSet(FixedBitSet other) {
      bits = new long[other.bits.length];
      System.arraycopy(other.bits, 0, bits, 0, bits.length);
      numBits = other.numBits;
    }
  
    @Override
    public DocIdSetIterator iterator() {
      return new OpenBitSetIterator(bits, bits.length);
    }
  
    public int length() {
      return numBits;
    }
  
    /** This DocIdSet implementation is cacheable. */
    @Override
    public boolean isCacheable() {
      return true;
    }
  
    /** Expert. */
    public long[] getBits() {
      return bits;
    }
  
    /** Returns number of set bits.  NOTE: this visits every
     *  long in the backing bits array, and the result is not
     *  internally cached! */
    public int cardinality() {
      return (int) BitUtil.pop_array(bits, 0, bits.length);
    }
  
    public boolean get(int index) {
      assert index >= 0 && index < numBits;
      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;
    }
  
    public void set(int index) {
      assert index >= 0 && index < numBits;
      int wordNum = index >> 6;      // div 64
      int bit = index & 0x3f;     // mod 64
      long bitmask = 1L << bit;
      bits[wordNum] |= bitmask;
    }
  
    public boolean getAndSet(int index) {
      assert index >= 0 && index < numBits;
      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;
    }
  
    public void clear(int index) {
      assert index >= 0 && index < numBits;
      int wordNum = index >> 6;
      int bit = index & 0x03f;
      long bitmask = 1L << bit;
      bits[wordNum] &= ~bitmask;
    }
  
    public boolean getAndClear(int index) {
      assert index >= 0 && index < numBits;
      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;
    }
  
    /** Returns the index of the first set bit starting at the index specified.
     *  -1 is returned if there are no more set bits.
     */
    public int nextSetBit(int index) {
      assert index >= 0 && index < numBits;
      int i = index >> 6;
      final int subIndex = index & 0x3f;      // index within the word
      long word = bits[i] >> subIndex;  // skip all the bits to the right of index
  
      if (word!=0) {
        return (i<<6) + subIndex + BitUtil.ntz(word);
      }
  
      while(++i < bits.length) {
        word = bits[i];
        if (word != 0) {
          return (i<<6) + BitUtil.ntz(word);
        }
      }
  
      return -1;
    }
  
    /** Returns the index of the last set bit before or on the index specified.
     *  -1 is returned if there are no more set bits.
     */
    public int prevSetBit(int index) {
      assert index >= 0 && index < numBits: "index=" + index + " numBits=" + numBits;
      int i = index >> 6;
      final int subIndex = index & 0x3f;  // index within the word
      long word = (bits[i] << (63-subIndex));  // skip all the bits to the left of index
  
      if (word != 0) {
        return (i << 6) + subIndex - Long.numberOfLeadingZeros(word); // See LUCENE-3197
      }
  
      while (--i >= 0) {
        word = bits[i];
        if (word !=0 ) {
          return (i << 6) + 63 - Long.numberOfLeadingZeros(word);
        }
      }
  
      return -1;
    }
  
    /** Does in-place OR of the bits provided by the
     *  iterator. */
    public void or(DocIdSetIterator iter) throws IOException {
      if (iter instanceof OpenBitSetIterator && iter.docID() == -1) {
        final OpenBitSetIterator obs = (OpenBitSetIterator) iter;
        or(obs.arr, obs.words);
        // advance after last doc that would be accepted if standard
        // iteration is used (to exhaust it):
        obs.advance(numBits);
      } else {
        int doc;
        while ((doc = iter.nextDoc()) < numBits) {
          set(doc);
        }
      }
    }
  
    /** this = this OR other */
    public void or(FixedBitSet other) {
      or(other.bits, other.bits.length);
    }
    
    private void or(final long[] otherArr, final int otherLen) {
      final long[] thisArr = this.bits;
      int pos = Math.min(thisArr.length, otherLen);
      while (--pos >= 0) {
        thisArr[pos] |= otherArr[pos];
      }
    }
  
    /** Does in-place AND of the bits provided by the
     *  iterator. */
    public void and(DocIdSetIterator iter) throws IOException {
      if (iter instanceof OpenBitSetIterator && iter.docID() == -1) {
        final OpenBitSetIterator obs = (OpenBitSetIterator) iter;
        and(obs.arr, obs.words);
        // advance after last doc that would be accepted if standard
        // iteration is used (to exhaust it):
        obs.advance(numBits);
      } else {
        if (numBits == 0) return;
        int disiDoc, bitSetDoc = nextSetBit(0);
        while (bitSetDoc != -1 && (disiDoc = iter.advance(bitSetDoc)) < numBits) {
          clear(bitSetDoc, disiDoc);
          disiDoc++;
          bitSetDoc = (disiDoc < numBits) ? nextSetBit(disiDoc) : -1;
        }
        if (bitSetDoc != -1) {
          clear(bitSetDoc, numBits);
        }
      }
    }
  
    /** this = this AND other */
    public void and(FixedBitSet other) {
      and(other.bits, other.bits.length);
    }
    
    private void and(final long[] otherArr, final int otherLen) {
      final long[] thisArr = this.bits;
      int pos = Math.min(thisArr.length, otherLen);
      while(--pos >= 0) {
        thisArr[pos] &= otherArr[pos];
      }
      if (thisArr.length > otherLen) {
        Arrays.fill(thisArr, otherLen, thisArr.length, 0L);
      }
    }
  
    /** Does in-place AND NOT of the bits provided by the
     *  iterator. */
    public void andNot(DocIdSetIterator iter) throws IOException {
      if (iter instanceof OpenBitSetIterator && iter.docID() == -1) {
        final OpenBitSetIterator obs = (OpenBitSetIterator) iter;
        andNot(obs.arr, obs.words);
        // advance after last doc that would be accepted if standard
        // iteration is used (to exhaust it):
        obs.advance(numBits);
      } else {
        int doc;
        while ((doc = iter.nextDoc()) < numBits) {
          clear(doc);
        }
      }
    }
  
    /** this = this AND NOT other */
    public void andNot(FixedBitSet other) {
      andNot(other.bits, other.bits.length);
    }
    
    private void andNot(final long[] otherArr, final int otherLen) {
      final long[] thisArr = this.bits;
      int pos = Math.min(thisArr.length, otherLen);
      while(--pos >= 0) {
        thisArr[pos] &= ~otherArr[pos];
      }
    }
  
    // NOTE: no .isEmpty() here because that's trappy (ie,
    // typically isEmpty is low cost, but this one wouldn't
    // be)
  
    /** Flips a range of bits
     *
     * @param startIndex lower index
     * @param endIndex one-past the last bit to flip
     */
    public void flip(int startIndex, int endIndex) {
      assert startIndex >= 0 && startIndex < numBits;
      assert endIndex >= 0 && endIndex <= numBits;
      if (endIndex <= startIndex) {
        return;
      }
  
      int startWord = startIndex >> 6;
      int endWord = (endIndex-1) >> 6;
  
      /*** Grrr, java shifting wraps around so -1L>>>64 == -1
       * for that reason, make sure not to use endmask if the bits to flip will
       * be zero in the last word (redefine endWord to be the last changed...)
      long startmask = -1L << (startIndex & 0x3f);     // example: 11111...111000
      long endmask = -1L >>> (64-(endIndex & 0x3f));   // example: 00111...111111
      ***/
  
      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;
  
      for (int i=startWord+1; i<endWord; i++) {
        bits[i] = ~bits[i];
      }
  
      bits[endWord] ^= endmask;
    }
  
    /** Sets a range of bits
     *
     * @param startIndex lower index
     * @param endIndex one-past the last bit to set
     */
    public void set(int startIndex, int endIndex) {
      assert startIndex >= 0 && startIndex < numBits;
      assert endIndex >= 0 && endIndex <= numBits;
      if (endIndex <= startIndex) {
        return;
      }
  
      int startWord = startIndex >> 6;
      int endWord = (endIndex-1) >> 6;
  
      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;
    }
  
    /** Clears a range of bits.
     *
     * @param startIndex lower index
     * @param endIndex one-past the last bit to clear
     */
    public void clear(int startIndex, int endIndex) {
      assert startIndex >= 0 && startIndex < numBits;
      assert endIndex >= 0 && endIndex <= numBits;
      if (endIndex <= startIndex) {
        return;
      }
  
      int startWord = startIndex >> 6;
      int endWord = (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;
      Arrays.fill(bits, startWord+1, endWord, 0L);
      bits[endWord] &= endmask;
    }
  
    @Override
    public Object clone() {
      return new FixedBitSet(this);
    }
  
    /** returns true if both sets have the same bits set */
    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (!(o instanceof FixedBitSet)) {
        return false;
      }
      FixedBitSet other = (FixedBitSet) o;
      if (numBits != other.length()) {
        return false;
      }
      return Arrays.equals(bits, other.bits);
    }
  
    @Override
    public int hashCode() {
      long h = 0;
      for (int i = bits.length; --i>=0;) {
        h ^= bits[i];
        h = (h << 1) | (h >>> 63); // rotate left
      }
      // fold leftmost bits into right and add a constant to prevent
      // empty sets from returning 0, which is too common.
      return (int) ((h>>32) ^ h) + 0x98761234;
    }
  }
  