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.

  • Constructor Details

    • FixedBitSet

      public FixedBitSet(int numBits)
      Creates a new LongBitSet. 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 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)
      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 numBits)
      If the given FixedBitSet is large enough to hold numBits+1, returns the given bits, otherwise returns a new FixedBitSet which can hold the requested number of bits.

      NOTE: the returned bitset reuses the underlying long[] of the given bits if possible. Also, calling length() on the returned bits may return a value greater than numBits.

    • 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.

    • 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
      Return the memory usage of this object in bytes. 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

    • 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

    • 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.
      Specified by:
      nextSetBit 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

    • 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.