FixedBitSet (Lucene 10.5.1 core API)
Description: declaration: package: org.apache.lucene.util, class: FixedBitSet

Package org.apache.lucene.util

# Class FixedBitSet

java.lang.Object
org.apache.lucene.util.BitSet
org.apache.lucene.util.FixedBitSet

All Implemented Interfaces:
  `Accountable`, `Bits`

public final class FixedBitSet extends BitSet
BitSet of fixed length (numBits), backed by accessible (`getBits()`) long[], accessed with an int index, implementing `Bits` and `DocIdSet`. If you need to manage more than 2.1B bits, use `LongBitSet`.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

- ## Nested Class Summary

  ## Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits

  `Bits.MatchAllBits, Bits.MatchNoBits`

- ## Field Summary

  ### Fields inherited from interface org.apache.lucene.util.Accountable

  `NULL_ACCOUNTABLE`

  ### Fields inherited from interface org.apache.lucene.util.Bits

  `EMPTY_ARRAY`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `FixedBitSet(int numBits)`
  Creates a new FixedBitSet.
  `FixedBitSet(long[] storedBits, int numBits)`
  Creates a new FixedBitSet using the provided long[] array as backing store.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `and(FixedBitSet other)`
  this = this AND other
  `void`
  `andNot(DocIdSetIterator iter)`
  `void`
  `andNot(FixedBitSet other)`
  this = this AND NOT other
  `static long`
  `andNotCount(FixedBitSet a, FixedBitSet b)`
  Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))".
  `static void`
  `andRange(FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length)`
  And `length` bits starting at `sourceFrom` from `source` into `dest` starting at `destFrom`.
  `void`
  `applyMask(FixedBitSet bitSet, int offset)`
  Apply this `Bits` instance to the given `FixedBitSet`, which starts at the given `offset`.
  `int`
  `approximateCardinality()`
  Return an approximation of the cardinality of this set.
  `Bits`
  `asReadOnlyBits()`
  Convert this instance to read-only `Bits`.
  `static int`
  `bits2words(int numBits)`
  returns the number of 64 bit words it would take to hold numBits
  `int`
  `cardinality()`
  Returns number of set bits.
  `int`
  `cardinality(int from, int to)`
  Return the number of set bits between indexes `from` inclusive and `to` exclusive.
  `void`
  `clear()`
  Clear all the bits of the set.
  `void`
  `clear(int index)`
  Clear the bit at `i`.
  `void`
  `clear(int startIndex, int endIndex)`
  Clears a range of bits.
  `FixedBitSet`
  `clone()`
  `static FixedBitSet`
  `copyOf(Bits bits)`
  Make a copy of the given bits.
  `static FixedBitSet`
  `ensureCapacity(FixedBitSet bits, int desiredBit)`
  `static FixedBitSet`
  `ensureCapacityAndClear(FixedBitSet bits, int desiredBit)`
  `boolean`
  `equals(Object o)`
  `void`
  `flip(int index)`
  Flip the bit at the provided index.
  `void`
  `flip(int startIndex, int endIndex)`
  Flips a range of bits
  `void`
  `forEach(int from, int to, int base, CheckedIntConsumer<IOException> consumer)`
  For each set bit from `from` inclusive to `to` exclusive, add `base` to the bit index and call `consumer` on it.
  `boolean`
  `get(int index)`
  Returns the value of the bit with the specified `index`.
  `boolean`
  `getAndClear(int index)`
  `boolean`
  `getAndSet(int index)`
  Set the bit at `i`, returning `true` if it was previously set.
  `long[]`
  `getBits()`
  Expert.
  `int`
  `hashCode()`
  `static long`
  `intersectionCount(FixedBitSet a, FixedBitSet b)`
  Returns the popcount or cardinality of the intersection of the two sets.
  `boolean`
  `intersects(FixedBitSet other)`
  returns true if the sets have any elements in common
  `int`
  `intoArray(int from, int to, int base, int[] array)`
  Converts set bits in this bitset to an array of document IDs.
  `int`
  `length()`
  Returns the number of bits in this set
  `int`
  `nextClearBit(int index)`
  Returns the index of the first unset (clear) bit at or after `index`, or `DocIdSetIterator.NO_MORE_DOCS` if every bit in `[index, length())` is set.
  `int`
  `nextClearBit(int start, int upperBound)`
  Returns the first unset bit in `[start, upperBound)`, or `DocIdSetIterator.NO_MORE_DOCS` if none.
  `int`
  `nextSetBit(int index)`
  Returns the index of the first set bit starting at the index specified.
  `int`
  `nextSetBit(int start, int upperBound)`
  Returns the index of the first set bit from start (inclusive) until end (exclusive).
  `void`
  `or(DocIdSetIterator iter)`
  Does in-place OR of the bits provided by the iterator.
  `void`
  `or(FixedBitSet other)`
  this = this OR other
  `void`
  `orMask(int startBit, long mask, int maskLen)`
  ORs a small mask of consecutive bits starting at `startBit`.
  `static void`
  `orRange(FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length)`
  Or `length` bits starting at `sourceFrom` from `source` into `dest` starting at `destFrom`.
  `int`
  `prevSetBit(int index)`
  Returns the index of the last set bit before or on the index specified.
  `long`
  `ramBytesUsed()`
  Returns an estimate of the JVM heap memory used by this object in bytes.
  `boolean`
  `scanIsEmpty()`
  Scans the backing store to check if all bits are clear.
  `void`
  `set(int index)`
  Set the bit at `i`.
  `void`
  `set(int startIndex, int endIndex)`
  Sets a range of bits
  `static long`
  `unionCount(FixedBitSet a, FixedBitSet b)`
  Returns the popcount or cardinality of the union of the two sets.
  `void`
  `xor(DocIdSetIterator iter)`
  Does in-place XOR of the bits provided by the iterator.
  `void`
  `xor(FixedBitSet other)`
  this = this XOR other

  ### Methods inherited from class org.apache.lucene.util.BitSet

  `checkUnpositioned, of`

  ### Methods inherited from class java.lang.Object

  `finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

  ### Methods inherited from interface org.apache.lucene.util.Accountable

  `getChildResources`

- ## Constructor Details

  - ### FixedBitSet

    public FixedBitSet(int numBits)
    Creates a new FixedBitSet. The internally allocated long array will be exactly the size needed to accommodate the numBits specified.
    Parameters:
      `numBits` - the number of bits needed

  - ### FixedBitSet

    public FixedBitSet(long[] storedBits, int numBits)
    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)
    Parameters:
      `storedBits` - the array to use as backing store
      `numBits` - the number of bits actually needed

- ## Method Details

  - ### ensureCapacity

    public static FixedBitSet ensureCapacity(FixedBitSet bits, int desiredBit)

  - ### ensureCapacityAndClear

    public static FixedBitSet ensureCapacityAndClear(FixedBitSet bits, int desiredBit)

  - ### bits2words

    public static int bits2words(int numBits)
    returns the number of 64 bit words it would take to hold numBits

  - ### intersectionCount

    public static long intersectionCount(FixedBitSet a, FixedBitSet b)
    Returns the popcount or cardinality of the intersection of the two sets. Neither set is modified.

  - ### unionCount

    public static long unionCount(FixedBitSet a, FixedBitSet b)
    Returns the popcount or cardinality of the union of the two sets. Neither set is modified.

  - ### andNotCount

    public static long andNotCount(FixedBitSet a, FixedBitSet b)
    Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))". Neither set is modified.

  - ### clear

    public void clear()
    Description copied from class: `BitSet`
    Clear all the bits of the set.

    Depending on the implementation, this may be significantly faster than clear(0, length).

    Overrides:
      `clear` in class `BitSet`

  - ### length

    public int length()
    Description copied from interface: `Bits`
    Returns the number of bits in this set

  - ### ramBytesUsed

    public long ramBytesUsed()
    Description copied from interface: `Accountable`
    Returns an estimate of the JVM heap memory used by this object in bytes. The method name uses "ram" for historical reasons; only JVM heap memory should be reported. Off-heap resources such as memory-mapped files or native direct buffers should not be included. Negative values are illegal.

  - ### getBits

    public long[] getBits()
    Expert.

  - ### cardinality

    public int cardinality()
    Returns number of set bits. NOTE: this visits every long in the backing bits array, and the result is not internally cached!
    Specified by:
      `cardinality` in class `BitSet`

  - ### cardinality

    public int cardinality(int from, int to)
    Return the number of set bits between indexes `from` inclusive and `to` exclusive.

  - ### approximateCardinality

    public int approximateCardinality()
    Description copied from class: `BitSet`
    Return an approximation of the cardinality of this set. Some implementations may trade accuracy for speed if they have the ability to estimate the cardinality of the set without iterating over all the data. The default implementation returns `BitSet.cardinality()`.
    Specified by:
      `approximateCardinality` in class `BitSet`

  - ### get

    public boolean get(int index)
    Description copied from interface: `Bits`
    Returns the value of the bit with the specified `index`.
    Parameters:
      `index` - index, should be non-negative and < `Bits.length()`. The result of passing negative or out of bounds values is undefined by this interface, just don't do it!
    Returns:
      `true` if the bit is set, `false` otherwise.

  - ### set

    public void set(int index)
    Description copied from class: `BitSet`
    Set the bit at `i`.
    Specified by:
      `set` in class `BitSet`

  - ### orMask

    public void orMask(int startBit, long mask, int maskLen)
    ORs a small mask of consecutive bits starting at `startBit`. The mask must have at most `maskLen` significant bits. This is useful for bulk-setting bits from a SIMD comparison result without per-bit extraction.
    Parameters:
      `startBit` - the first bit position to set (inclusive)
      `mask` - the bitmask to OR in, where bit 0 corresponds to startBit
      `maskLen` - the number of significant bits in the mask (e.g., 2, 4, or 8)

  - ### getAndSet

    public boolean getAndSet(int index)
    Description copied from class: `BitSet`
    Set the bit at `i`, returning `true` if it was previously set.
    Specified by:
      `getAndSet` in class `BitSet`

  - ### clear

    public void clear(int index)
    Description copied from class: `BitSet`
    Clear the bit at `i`.
    Specified by:
      `clear` in class `BitSet`

  - ### getAndClear

    public boolean getAndClear(int index)

  - ### nextSetBit

    public int nextSetBit(int index)
    Description copied from class: `BitSet`
    Returns the index of the first set bit starting at the index specified. `DocIdSetIterator.NO_MORE_DOCS` is returned if there are no more set bits.
    Overrides:
      `nextSetBit` in class `BitSet`

  - ### nextSetBit

    public int nextSetBit(int start, int upperBound)
    Description copied from class: `BitSet`
    Returns the index of the first set bit from start (inclusive) until end (exclusive). `DocIdSetIterator.NO_MORE_DOCS` is returned if there are no more set bits.
    Specified by:
      `nextSetBit` in class `BitSet`

  - ### nextClearBit

    public int nextClearBit(int index)
    Description copied from class: `BitSet`
    Returns the index of the first unset (clear) bit at or after `index`, or `DocIdSetIterator.NO_MORE_DOCS` if every bit in `[index, length())` is set.
    Overrides:
      `nextClearBit` in class `BitSet`

  - ### nextClearBit

    public int nextClearBit(int start, int upperBound)
    Description copied from class: `BitSet`
    Returns the first unset bit in `[start, upperBound)`, or `DocIdSetIterator.NO_MORE_DOCS` if none.
    Specified by:
      `nextClearBit` in class `BitSet`

  - ### prevSetBit

    public int prevSetBit(int index)
    Description copied from class: `BitSet`
    Returns the index of the last set bit before or on the index specified. -1 is returned if there are no more set bits.
    Specified by:
      `prevSetBit` in class `BitSet`

  - ### or

    public void or(DocIdSetIterator iter) throws IOException
    Description copied from class: `BitSet`
    Does in-place OR of the bits provided by the iterator. The state of the iterator after this operation terminates is undefined.
    Overrides:
      `or` in class `BitSet`
    Throws:
      `IOException`

  - ### orRange

    public static void orRange(FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length)
    Or `length` bits starting at `sourceFrom` from `source` into `dest` starting at `destFrom`.

  - ### andRange

    public static void andRange(FixedBitSet source, int sourceFrom, FixedBitSet dest, int destFrom, int length)
    And `length` bits starting at `sourceFrom` from `source` into `dest` starting at `destFrom`.

  - ### or

    public void or(FixedBitSet other)
    this = this OR other

  - ### xor

    public void xor(FixedBitSet other)
    this = this XOR other

  - ### xor

    public void xor(DocIdSetIterator iter) throws IOException
    Does in-place XOR of the bits provided by the iterator.
    Throws:
      `IOException`

  - ### intersects

    public boolean intersects(FixedBitSet other)
    returns true if the sets have any elements in common

  - ### and

    public void and(FixedBitSet other)
    this = this AND other

  - ### andNot

    public void andNot(DocIdSetIterator iter) throws IOException
    Throws:
      `IOException`

  - ### andNot

    public void andNot(FixedBitSet other)
    this = this AND NOT other

  - ### scanIsEmpty

    public boolean scanIsEmpty()
    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).
    Returns:
      true if all bits are clear.

  - ### flip

    public void flip(int startIndex, int endIndex)
    Flips a range of bits
    Parameters:
      `startIndex` - lower index
      `endIndex` - one-past the last bit to flip

  - ### flip

    public void flip(int index)
    Flip the bit at the provided index.

  - ### set

    public void set(int startIndex, int endIndex)
    Sets a range of bits
    Parameters:
      `startIndex` - lower index
      `endIndex` - one-past the last bit to set

  - ### clear

    public void clear(int startIndex, int endIndex)
    Description copied from class: `BitSet`
    Clears a range of bits.
    Specified by:
      `clear` in class `BitSet`
    Parameters:
      `startIndex` - lower index
      `endIndex` - one-past the last bit to clear

  - ### clone

    public FixedBitSet clone()
    Overrides:
      `clone` in class `Object`

  - ### equals

    public boolean equals(Object o)
    Overrides:
      `equals` in class `Object`

  - ### hashCode

    public int hashCode()
    Overrides:
      `hashCode` in class `Object`

  - ### copyOf

    public static FixedBitSet copyOf(Bits bits)
    Make a copy of the given bits.

  - ### asReadOnlyBits

    public Bits asReadOnlyBits()
    Convert this instance to read-only `Bits`. This is useful in the case that this `FixedBitSet` is returned as a `Bits` instance, to make sure that consumers may not get write access back by casting to a `FixedBitSet`. NOTE: Changes to this `FixedBitSet` will be reflected on the returned `Bits`.

  - ### applyMask

    public void applyMask(FixedBitSet bitSet, int offset)
    Description copied from interface: `Bits`
    Apply this `Bits` instance to the given `FixedBitSet`, which starts at the given `offset`.

    This should behave the same way as the default implementation, which does the following:

         for (int i = bitSet.nextSetBit(0);
             i != DocIdSetIterator.NO_MORE_DOCS;
             i = i + 1 >= bitSet.length() ? DocIdSetIterator.NO_MORE_DOCS : bitSet.nextSetBit(i + 1)) {
           if (get(offset + i) == false) {
             bitSet.clear(i);
           }
         }

  - ### forEach

    public void forEach(int from, int to, int base, CheckedIntConsumer<IOException> consumer) throws IOException
    For each set bit from `from` inclusive to `to` exclusive, add `base` to the bit index and call `consumer` on it. This is internally used by queries that use bit sets as intermediate representations of their matches.
    Throws:
      `IOException`

  - ### intoArray

    public int intoArray(int from, int to, int base, int[] array)
    Converts set bits in this bitset to an array of document IDs. Only processes bits from index `from` (inclusive) to `to` (exclusive) and returns the number of bits copied.

    Each set bit's position is converted to a document ID by adding the `base` value and stored in the provided `array`. This method stops when there are no more set bits before `to` or when there is no capacity left in the given `array`, whichever comes first.