Package org.apache.lucene.util

Class FixedBitSet

  • All Implemented Interfaces:
    Bits
    public final class FixedBitSet
extends DocIdSet
implements Bits
    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.

    • Constructor Detail

      • FixedBitSet

        public FixedBitSet​(int numBits)

      • FixedBitSet

        public FixedBitSet​(long[] storedBits,
                   int numBits)

    • Method Detail

      • ensureCapacity

        public static FixedBitSet ensureCapacity​(FixedBitSet bits,
                                         int numBits)
        If the given FixedBitSet is large enough to hold numBits, 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.

      • bits

        public Bits bits()
        Description copied from class: DocIdSet
        Optionally provides a Bits interface for random access to matching documents.
        Overrides:
        bits in class DocIdSet
        Returns:
        null, if this DocIdSet does not support random access. In contrast to DocIdSet.iterator(), a return value of null does not imply that no documents match the filter! The default implementation does not provide random access, so you only need to implement this method if your DocIdSet can guarantee random access to every docid in O(1) time without external disk access (as Bits interface cannot throw IOException). This is generally true for bit sets like FixedBitSet, which return itself if they are used as DocIdSet.

      • length

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

      • isCacheable

        public boolean isCacheable()
        This DocIdSet implementation is cacheable.
        Overrides:
        isCacheable in class DocIdSet

      • 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!

      • get

        public boolean get​(int index)
        Description copied from interface: Bits
        Returns the value of the bit with the specified index.
        Specified by:
        get in interface Bits
        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)

      • getAndSet

        public boolean getAndSet​(int index)

      • clear

        public void clear​(int index)

      • getAndClear

        public boolean getAndClear​(int index)

      • nextSetBit

        public int nextSetBit​(int index)
        Returns the index of the first set bit starting at the index specified. -1 is returned if there are no more set bits.

      • prevSetBit

        public int prevSetBit​(int index)
        Returns the index of the last set bit before or on the index specified. -1 is returned if there are no more set bits.

      • or

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

      • xor

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

      • 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​(FixedBitSet other)
        this = this AND NOT other

      • 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

      • 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)
        Clears a range of bits.
        Parameters:
        startIndex - lower index
        endIndex - one-past the last bit to clear

      • equals

        public boolean equals​(Object o)
        returns true if both sets have the same bits set
        Overrides:
        equals in class Object

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object