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/*
* 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 java.util.Objects;
import org.apache.lucene.search.CheckedIntConsumer;
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 {
private static final long BASE_RAM_BYTES_USED =
RamUsageEstimator.shallowSizeOfInstance(FixedBitSet.class);
// An array that is small enough to use reasonable amounts of RAM and large enough to allow
// Arrays#mismatch to use SIMD instructions and multiple registers under the hood.
private static final long[] ZEROES = new long[32];
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.
*
* NOTE: 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) {
// I.e.: get the word-offset of the last bit and add one (make sure to use >> so 0
// returns 0!)
return ((numBits - 1) >> 6) + 1;
}
/**
* 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!
long tot = 0;
final int numCommonWords = Math.min(a.numWords, b.numWords);
for (int i = 0; i < numCommonWords; ++i) {
tot += Long.bitCount(a.bits[i] & b.bits[i]);
}
return tot;
}
/** 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 = 0;
final int numCommonWords = Math.min(a.numWords, b.numWords);
for (int i = 0; i < numCommonWords; ++i) {
tot += Long.bitCount(a.bits[i] | b.bits[i]);
}
for (int i = numCommonWords; i < a.numWords; ++i) {
tot += Long.bitCount(a.bits[i]);
}
for (int i = numCommonWords; i < b.numWords; ++i) {
tot += Long.bitCount(b.bits[i]);
}
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 = 0;
final int numCommonWords = Math.min(a.numWords, b.numWords);
for (int i = 0; i < numCommonWords; ++i) {
tot += Long.bitCount(a.bits[i] & ~b.bits[i]);
}
for (int i = numCommonWords; i < a.numWords; ++i) {
tot += Long.bitCount(a.bits[i]);
}
return tot;
}
/**
* Creates a new FixedBitSet. 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 FixedBitSet 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();
}
@Override
public void clear() {
Arrays.fill(bits, 0L);
}
/**
* 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!
long tot = 0;
for (int i = 0; i < numWords; ++i) {
tot += Long.bitCount(bits[i]);
}
return Math.toIntExact(tot);
}
/**
* Return the number of set bits between indexes {@code from} inclusive and {@code to} exclusive.
*/
public int cardinality(int from, int to) {
Objects.checkFromToIndex(from, to, length());
int cardinality = 0;
// First, align `from` with a word start, ie. a multiple of Long.SIZE (64)
if ((from & 0x3F) != 0) {
long bits = this.bits[from >> 6] >>> from;
int numBitsTilNextWord = -from & 0x3F;
if (to - from < numBitsTilNextWord) {
bits &= (1L << (to - from)) - 1L;
return Long.bitCount(bits);
}
cardinality += Long.bitCount(bits);
from += numBitsTilNextWord;
assert (from & 0x3F) == 0;
}
for (int i = from >> 6, end = to >> 6; i < end; ++i) {
cardinality += Long.bitCount(bits[i]);
}
// Now handle bits between the last complete word and to
if ((to & 0x3F) != 0) {
long bits = this.bits[to >> 6] << -to;
cardinality += Long.bitCount(bits);
}
return cardinality;
}
@Override
public int approximateCardinality() {
// Naive sampling: compute the number of bits that are set on the first 16 longs every 1024
// longs and scale the result by 1024/16.
// This computes the pop count on ranges instead of single longs in order to take advantage of
// vectorization.
final int rangeLength = 16;
final int interval = 1024;
if (numWords <= interval) {
return cardinality();
}
long popCount = 0;
int maxWord;
for (maxWord = 0; maxWord + interval < numWords; maxWord += interval) {
for (int i = 0; i < rangeLength; ++i) {
popCount += Long.bitCount(bits[maxWord + i]);
}
}
popCount *= (interval / rangeLength) * numWords / maxWord;
return (int) popCount;
}
@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;
}
@Override
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;
}
@Override
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) {
// Override with a version that skips the bound check on the result since we know it will not
// go OOB:
return nextSetBitInRange(index, numBits);
}
@Override
public int nextSetBit(int start, int upperBound) {
int res = nextSetBitInRange(start, upperBound);
return res < upperBound ? res : DocIdSetIterator.NO_MORE_DOCS;
}
/**
* Returns the next set bit in the specified range, but treats `upperBound` as a best-effort hint
* rather than a hard requirement. Note that this may return a result that is >= upperBound in
* some cases, so callers must add their own check if `upperBound` is a hard requirement.
*/
private int nextSetBitInRange(int start, int upperBound) {
// Depends on the ghost bits being clear!
assert start >= 0 && start < numBits : "index=" + start + ", numBits=" + numBits;
assert start < upperBound : "index=" + start + ", upperBound=" + upperBound;
assert upperBound <= numBits : "upperBound=" + upperBound + ", numBits=" + numBits;
int i = start >> 6;
long word = bits[i] >> start; // skip all the bits to the right of index
if (word != 0) {
return start + Long.numberOfTrailingZeros(word);
}
int limit = upperBound == numBits ? numWords : bits2words(upperBound);
while (++i < limit) {
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 {
checkUnpositioned(iter);
iter.nextDoc();
iter.intoBitSet(DocIdSetIterator.NO_MORE_DOCS, this, 0);
}
/** Read {@code numBits} (between 1 and 63) bits from {@code bitSet} at {@code from}. */
private static long readNBits(long[] bitSet, int from, int numBits) {
assert numBits > 0 && numBits < Long.SIZE;
long bits = bitSet[from >> 6] >>> from;
int numBitsSoFar = Long.SIZE - (from & 0x3F);
if (numBitsSoFar < numBits) {
bits |= bitSet[(from >> 6) + 1] << -from;
}
return bits & ((1L << numBits) - 1);
}
/**
* Or {@code length} bits starting at {@code sourceFrom} from {@code source} into {@code dest}
* starting at {@code destFrom}.
*/
public static void orRange(
FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length) {
assert length >= 0;
Objects.checkFromIndexSize(sourceFrom, length, source.length());
Objects.checkFromIndexSize(destFrom, length, dest.length());
if (length == 0) {
return;
}
long[] sourceBits = source.getBits();
long[] destBits = dest.getBits();
// First, align `destFrom` with a word start, ie. a multiple of Long.SIZE (64)
if ((destFrom & 0x3F) != 0) {
int numBitsNeeded = Math.min(-destFrom & 0x3F, length);
long bits = readNBits(sourceBits, sourceFrom, numBitsNeeded) << destFrom;
destBits[destFrom >> 6] |= bits;
sourceFrom += numBitsNeeded;
destFrom += numBitsNeeded;
length -= numBitsNeeded;
}
if (length == 0) {
return;
}
assert (destFrom & 0x3F) == 0;
// Now OR at the word level
int numFullWords = length >> 6;
int sourceWordFrom = sourceFrom >> 6;
int destWordFrom = destFrom >> 6;
// Note: these two for loops auto-vectorize
if ((sourceFrom & 0x3F) == 0) {
// sourceFrom and destFrom are both aligned with a long[]
for (int i = 0; i < numFullWords; ++i) {
destBits[destWordFrom + i] |= sourceBits[sourceWordFrom + i];
}
} else {
for (int i = 0; i < numFullWords; ++i) {
destBits[destWordFrom + i] |=
(sourceBits[sourceWordFrom + i] >>> sourceFrom)
| (sourceBits[sourceWordFrom + i + 1] << -sourceFrom);
}
}
sourceFrom += numFullWords << 6;
destFrom += numFullWords << 6;
length -= numFullWords << 6;
// Finally handle tail bits
if (length > 0) {
long bits = readNBits(sourceBits, sourceFrom, length);
destBits[destFrom >> 6] |= bits;
}
}
/**
* And {@code length} bits starting at {@code sourceFrom} from {@code source} into {@code dest}
* starting at {@code destFrom}.
*/
public static void andRange(
FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length) {
assert length >= 0 : length;
Objects.checkFromIndexSize(sourceFrom, length, source.length());
Objects.checkFromIndexSize(destFrom, length, dest.length());
if (length == 0) {
return;
}
long[] sourceBits = source.getBits();
long[] destBits = dest.getBits();
// First, align `destFrom` with a word start, ie. a multiple of Long.SIZE (64)
if ((destFrom & 0x3F) != 0) {
int numBitsNeeded = Math.min(-destFrom & 0x3F, length);
long bits = readNBits(sourceBits, sourceFrom, numBitsNeeded) << destFrom;
bits |= ~(((1L << numBitsNeeded) - 1) << destFrom);
destBits[destFrom >> 6] &= bits;
sourceFrom += numBitsNeeded;
destFrom += numBitsNeeded;
length -= numBitsNeeded;
}
if (length == 0) {
return;
}
assert (destFrom & 0x3F) == 0;
// Now AND at the word level
int numFullWords = length >> 6;
int sourceWordFrom = sourceFrom >> 6;
int destWordFrom = destFrom >> 6;
// Note: these two for loops auto-vectorize
if ((sourceFrom & 0x3F) == 0) {
// sourceFrom and destFrom are both aligned with a long[]
for (int i = 0; i < numFullWords; ++i) {
destBits[destWordFrom + i] &= sourceBits[sourceWordFrom + i];
}
} else {
for (int i = 0; i < numFullWords; ++i) {
destBits[destWordFrom + i] &=
(sourceBits[sourceWordFrom + i] >>> sourceFrom)
| (sourceBits[sourceWordFrom + i + 1] << -sourceFrom);
}
}
sourceFrom += numFullWords << 6;
destFrom += numFullWords << 6;
length -= numFullWords << 6;
// Finally handle tail bits
if (length > 0) {
long bits = readNBits(sourceBits, sourceFrom, length);
bits |= (~0L << length);
destBits[destFrom >> 6] &= bits;
}
}
/** this = this OR other */
public void or(FixedBitSet other) {
orRange(other, 0, this, 0, other.length());
}
/** 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 {
checkUnpositioned(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);
}
}
public void andNot(DocIdSetIterator iter) throws IOException {
if (BitSetIterator.getFixedBitSetOrNull(iter) != null) {
checkUnpositioned(iter);
final FixedBitSet bits = BitSetIterator.getFixedBitSetOrNull(iter);
assert bits != null;
andNot(bits);
} else if (iter instanceof DocBaseBitSetIterator) {
checkUnpositioned(iter);
DocBaseBitSetIterator baseIter = (DocBaseBitSetIterator) iter;
andNot(baseIter.getDocBase() >> 6, baseIter.getBitSet());
} else {
checkUnpositioned(iter);
for (int doc = iter.nextDoc(); doc != DocIdSetIterator.NO_MORE_DOCS; doc = iter.nextDoc()) {
clear(doc);
}
}
}
/** this = this AND NOT other */
public void andNot(FixedBitSet other) {
andNot(0, other.bits, other.numWords);
}
private void andNot(final int otherOffsetWords, FixedBitSet other) {
andNot(otherOffsetWords, other.bits, other.numWords);
}
private void andNot(final int otherOffsetWords, final long[] otherArr, final int otherNumWords) {
int pos = Math.min(numWords - otherOffsetWords, otherNumWords);
final long[] thisArr = this.bits;
while (--pos >= 0) {
thisArr[pos + otherOffsetWords] &= ~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 += ZEROES.length) {
int cmpLen = Math.min(ZEROES.length, bits.length - i);
if (Arrays.equals(bits, i, i + cmpLen, ZEROES, 0, cmpLen) == false) {
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;
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;
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;
// 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;
}
/** Make a copy of the given bits. */
public static FixedBitSet copyOf(Bits bits) {
if (bits instanceof FixedBits fixedBits) {
// restore the original FixedBitSet
bits = fixedBits.bitSet;
}
if (bits instanceof FixedBitSet) {
return ((FixedBitSet) bits).clone();
} else {
int length = bits.length();
FixedBitSet bitSet = new FixedBitSet(length);
bitSet.set(0, length);
for (int i = 0; i < length; ++i) {
if (bits.get(i) == false) {
bitSet.clear(i);
}
}
return bitSet;
}
}
/**
* Convert this instance to read-only {@link Bits}. This is useful in the case that this {@link
* FixedBitSet} is returned as a {@link Bits} instance, to make sure that consumers may not get
* write access back by casting to a {@link FixedBitSet}. NOTE: Changes to this {@link
* FixedBitSet} will be reflected on the returned {@link Bits}.
*/
public Bits asReadOnlyBits() {
return new FixedBits(bits, numBits);
}
@Override
public void applyMask(FixedBitSet bitSet, int offset) {
// Note: Some scorers don't track maxDoc and may thus call this method with an offset that is
// beyond bitSet.length()
int length = Math.min(bitSet.length(), length() - offset);
if (length >= 0) {
andRange(this, offset, bitSet, 0, length);
}
if (length < bitSet.length()
&& bitSet.nextSetBit(Math.max(0, length)) != DocIdSetIterator.NO_MORE_DOCS) {
throw new IllegalArgumentException("Some bits are set beyond the end of live docs");
}
}
/**
* For each set bit from {@code from} inclusive to {@code to} exclusive, add {@code base} to the
* bit index and call {@code consumer} on it. This is internally used by queries that use bit sets
* as intermediate representations of their matches.
*/
public void forEach(int from, int to, int base, CheckedIntConsumer consumer)
throws IOException {
Objects.checkFromToIndex(from, to, length());
// First, align `from` with a word start, ie. a multiple of Long.SIZE (64)
if ((from & 0x3F) != 0) {
long bits = this.bits[from >> 6] >>> from;
int numBitsTilNextWord = -from & 0x3F;
if (to - from < numBitsTilNextWord) {
// All bits are in a single word
bits &= (1L << (to - from)) - 1L;
forEach(bits, from + base, consumer);
return;
}
forEach(bits, from + base, consumer);
from += numBitsTilNextWord;
assert (from & 0x3F) == 0;
}
for (int i = from >> 6, end = to >> 6; i < end; ++i) {
forEach(bits[i], base + (i << 6), consumer);
}
// Now handle remaining bits in the last partial word
if ((to & 0x3F) != 0) {
long bits = this.bits[to >> 6] & ((1L << to) - 1);
forEach(bits, base + (to & ~0x3F), consumer);
}
}
private static void forEach(long bits, int base, CheckedIntConsumer consumer)
throws IOException {
while (bits != 0L) {
int ntz = Long.numberOfTrailingZeros(bits);
consumer.accept(base + ntz);
bits ^= 1L << ntz;
}
}
}