/*
* 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;
/**
* BitSet of fixed length (numBits), backed by accessible ({@link #getBits})
* long[], accessed with an int index, implementing {@link Bits} and
* {@link DocIdSet}. If you need to manage more than 2.1B bits, use
* {@link LongBitSet}.
*
* @lucene.internal
*/
public final class FixedBitSet extends BitSet implements MutableBits, Accountable {
private static final long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(FixedBitSet.class);
private final long[] bits; // Array of longs holding the bits
private final int numBits; // The number of bits in use
private final int numWords; // The exact number of longs needed to hold numBits (<= bits.length)
/**
* If the given {@link FixedBitSet} is large enough to hold {@code numBits+1},
* returns the given bits, otherwise returns a new {@link FixedBitSet} which
* can hold the requested number of bits.
* <p>
* <b>NOTE:</b> the returned bitset reuses the underlying {@code long[]} of
* the given {@code bits} if possible. Also, calling {@link #length()} on the
* returned bits may return a value greater than {@code numBits}.
*/
public static FixedBitSet ensureCapacity(FixedBitSet bits, int numBits) {
if (numBits < bits.numBits) {
return bits;
} else {
// Depends on the ghost bits being clear!
// (Otherwise, they may become visible in the new instance)
int numWords = bits2words(numBits);
long[] arr = bits.getBits();
if (numWords >= arr.length) {
arr = ArrayUtil.grow(arr, numWords + 1);
}
return new FixedBitSet(arr, arr.length << 6);
}
}
/** returns the number of 64 bit words it would take to hold numBits */
public static int bits2words(int numBits) {
return ((numBits - 1) >> 6) + 1; // I.e.: get the word-offset of the last bit and add one (make sure to use >> so 0 returns 0!)
}
/**
* Returns the popcount or cardinality of the intersection of the two sets.
* Neither set is modified.
*/
public static long intersectionCount(FixedBitSet a, FixedBitSet b) {
// Depends on the ghost bits being clear!
return BitUtil.pop_intersect(a.bits, b.bits, 0, Math.min(a.numWords, b.numWords));
}
/**
* Returns the popcount or cardinality of the union of the two sets. Neither
* set is modified.
*/
public static long unionCount(FixedBitSet a, FixedBitSet b) {
// Depends on the ghost bits being clear!
long tot = BitUtil.pop_union(a.bits, b.bits, 0, Math.min(a.numWords, b.numWords));
if (a.numWords < b.numWords) {
tot += BitUtil.pop_array(b.bits, a.numWords, b.numWords - a.numWords);
} else if (a.numWords > b.numWords) {
tot += BitUtil.pop_array(a.bits, b.numWords, a.numWords - b.numWords);
}
return tot;
}
/**
* Returns the popcount or cardinality of "a and not b" or
* "intersection(a, not(b))". Neither set is modified.
*/
public static long andNotCount(FixedBitSet a, FixedBitSet b) {
// Depends on the ghost bits being clear!
long tot = BitUtil.pop_andnot(a.bits, b.bits, 0, Math.min(a.numWords, b.numWords));
if (a.numWords > b.numWords) {
tot += BitUtil.pop_array(a.bits, b.numWords, a.numWords - b.numWords);
}
return tot;
}
/**
* Creates a new LongBitSet.
* The internally allocated long array will be exactly the size needed to accommodate the numBits specified.
* @param numBits the number of bits needed
*/
public FixedBitSet(int numBits) {
this.numBits = numBits;
bits = new long[bits2words(numBits)];
numWords = bits.length;
}
/**
* Creates a new LongBitSet using the provided long[] array as backing store.
* The storedBits array must be large enough to accommodate the numBits specified, but may be larger.
* In that case the 'extra' or 'ghost' bits must be clear (or they may provoke spurious side-effects)
* @param storedBits the array to use as backing store
* @param numBits the number of bits actually needed
*/
public FixedBitSet(long[] storedBits, int numBits) {
this.numWords = bits2words(numBits);
if (numWords > storedBits.length) {
throw new IllegalArgumentException("The given long array is too small to hold " + numBits + " bits");
}
this.numBits = numBits;
this.bits = storedBits;
assert verifyGhostBitsClear();
}
/**
* Checks if the bits past numBits are clear.
* Some methods rely on this implicit assumption: search for "Depends on the ghost bits being clear!"
* @return true if the bits past numBits are clear.
*/
private boolean verifyGhostBitsClear() {
for (int i = numWords; i < bits.length; i++) {
if (bits[i] != 0) return false;
}
if ((numBits & 0x3f) == 0) return true;
long mask = -1L << numBits;
return (bits[numWords - 1] & mask) == 0;
}
@Override
public int length() {
return numBits;
}
@Override
public long ramBytesUsed() {
return BASE_RAM_BYTES_USED + RamUsageEstimator.sizeOf(bits);
}
/** 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!
*/
@Override
public int cardinality() {
// Depends on the ghost bits being clear!
return (int) BitUtil.pop_array(bits, 0, numWords);
}
@Override
public boolean get(int index) {
assert index >= 0 && index < numBits: "index=" + index + ", numBits=" + 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.
long bitmask = 1L << index;
return (bits[i] & bitmask) != 0;
}
public void set(int index) {
assert index >= 0 && index < numBits: "index=" + index + ", numBits=" + numBits;
int wordNum = index >> 6; // div 64
long bitmask = 1L << index;
bits[wordNum] |= bitmask;
}
public boolean getAndSet(int index) {
assert index >= 0 && index < numBits: "index=" + index + ", numBits=" + numBits;
int wordNum = index >> 6; // div 64
long bitmask = 1L << index;
boolean val = (bits[wordNum] & bitmask) != 0;
bits[wordNum] |= bitmask;
return val;
}
@Override
public void clear(int index) {
assert index >= 0 && index < numBits: "index=" + index + ", numBits=" + numBits;
int wordNum = index >> 6;
long bitmask = 1L << index;
bits[wordNum] &= ~bitmask;
}
public boolean getAndClear(int index) {
assert index >= 0 && index < numBits: "index=" + index + ", numBits=" + numBits;
int wordNum = index >> 6; // div 64
long bitmask = 1L << index;
boolean val = (bits[wordNum] & bitmask) != 0;
bits[wordNum] &= ~bitmask;
return val;
}
@Override
public int nextSetBit(int index) {
// Depends on the ghost bits being clear!
assert index >= 0 && index < numBits : "index=" + index + ", numBits=" + numBits;
int i = index >> 6;
long word = bits[i] >> index; // skip all the bits to the right of index
if (word!=0) {
return index + Long.numberOfTrailingZeros(word);
}
while(++i < numWords) {
word = bits[i];
if (word != 0) {
return (i<<6) + Long.numberOfTrailingZeros(word);
}
}
return DocIdSetIterator.NO_MORE_DOCS;
}
@Override
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;
}
@Override
public void or(DocIdSetIterator iter) throws IOException {
if (BitSetIterator.getFixedBitSetOrNull(iter) != null) {
assertUnpositioned(iter);
final FixedBitSet bits = BitSetIterator.getFixedBitSetOrNull(iter);
or(bits);
} else {
super.or(iter);
}
}
/** this = this OR other */
public void or(FixedBitSet other) {
or(other.bits, other.numWords);
}
private void or(final long[] otherArr, final int otherNumWords) {
assert otherNumWords <= numWords : "numWords=" + numWords + ", otherNumWords=" + otherNumWords;
final long[] thisArr = this.bits;
int pos = Math.min(numWords, otherNumWords);
while (--pos >= 0) {
thisArr[pos] |= otherArr[pos];
}
}
/** this = this XOR other */
public void xor(FixedBitSet other) {
xor(other.bits, other.numWords);
}
/** Does in-place XOR of the bits provided by the iterator. */
public void xor(DocIdSetIterator iter) throws IOException {
assertUnpositioned(iter);
if (BitSetIterator.getFixedBitSetOrNull(iter) != null) {
final FixedBitSet bits = BitSetIterator.getFixedBitSetOrNull(iter);
xor(bits);
} else {
int doc;
while ((doc = iter.nextDoc()) < numBits) {
flip(doc);
}
}
}
private void xor(long[] otherBits, int otherNumWords) {
assert otherNumWords <= numWords : "numWords=" + numWords + ", other.numWords=" + otherNumWords;
final long[] thisBits = this.bits;
int pos = Math.min(numWords, otherNumWords);
while (--pos >= 0) {
thisBits[pos] ^= otherBits[pos];
}
}
/** returns true if the sets have any elements in common */
public boolean intersects(FixedBitSet other) {
// Depends on the ghost bits being clear!
int pos = Math.min(numWords, other.numWords);
while (--pos>=0) {
if ((bits[pos] & other.bits[pos]) != 0) return true;
}
return false;
}
/** this = this AND other */
public void and(FixedBitSet other) {
and(other.bits, other.numWords);
}
private void and(final long[] otherArr, final int otherNumWords) {
final long[] thisArr = this.bits;
int pos = Math.min(this.numWords, otherNumWords);
while(--pos >= 0) {
thisArr[pos] &= otherArr[pos];
}
if (this.numWords > otherNumWords) {
Arrays.fill(thisArr, otherNumWords, this.numWords, 0L);
}
}
/** this = this AND NOT other */
public void andNot(FixedBitSet other) {
andNot(other.bits, other.numWords);
}
private void andNot(final long[] otherArr, final int otherNumWords) {
final long[] thisArr = this.bits;
int pos = Math.min(this.numWords, otherNumWords);
while(--pos >= 0) {
thisArr[pos] &= ~otherArr[pos];
}
}
/**
* Scans the backing store to check if all bits are clear.
* The method is deliberately not called "isEmpty" to emphasize it is not low cost (as isEmpty usually is).
* @return true if all bits are clear.
*/
public boolean scanIsEmpty() {
// This 'slow' implementation is still faster than any external one could be
// (e.g.: (bitSet.length() == 0 || bitSet.nextSetBit(0) == -1))
// especially for small BitSets
// Depends on the ghost bits being clear!
final int count = numWords;
for (int i = 0; i < count; i++) {
if (bits[i] != 0) return false;
}
return true;
}
/** 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 uses only the lower 6 bits of the count 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 since only the lowest 6 bits are used
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;
}
/** Flip the bit at the provided index. */
public void flip(int index) {
assert index >= 0 && index < numBits: "index=" + index + " numBits=" + numBits;
int wordNum = index >> 6; // div 64
long bitmask = 1L << index; // mod 64 is implicit
bits[wordNum] ^= bitmask;
}
/** 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 : "startIndex=" + startIndex + ", numBits=" + numBits;
assert endIndex >= 0 && endIndex <= numBits : "endIndex=" + endIndex + ", numBits=" + 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 since only the lowest 6 bits are used
if (startWord == endWord) {
bits[startWord] |= (startmask & endmask);
return;
}
bits[startWord] |= startmask;
Arrays.fill(bits, startWord+1, endWord, -1L);
bits[endWord] |= endmask;
}
@Override
public void clear(int startIndex, int endIndex) {
assert startIndex >= 0 && startIndex < numBits : "startIndex=" + startIndex + ", numBits=" + numBits;
assert endIndex >= 0 && endIndex <= numBits : "endIndex=" + endIndex + ", numBits=" + 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 since only the lowest 6 bits are used
// 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 FixedBitSet clone() {
long[] bits = new long[this.bits.length];
System.arraycopy(this.bits, 0, bits, 0, numWords);
return new FixedBitSet(bits, numBits);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof FixedBitSet)) {
return false;
}
FixedBitSet other = (FixedBitSet) o;
if (numBits != other.numBits) {
return false;
}
// Depends on the ghost bits being clear!
return Arrays.equals(bits, other.bits);
}
@Override
public int hashCode() {
// Depends on the ghost bits being clear!
long h = 0;
for (int i = numWords; --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;
}
}