Package org.apache.lucene.util

Class BitUtil

java.lang.Object
org.apache.lucene.util.BitUtil
public final class BitUtil extends Object
A variety of high efficiency bit twiddling routines.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final long
    MAGIC0
     
    private static final long
    MAGIC1
     
    private static final long
    MAGIC2
     
    private static final long
    MAGIC3
     
    private static final long
    MAGIC4
     
    private static final long
    MAGIC5
     
    private static final long
    MAGIC6
     
    private static final long
    SHIFT0
     
    private static final long
    SHIFT1
     
    private static final long
    SHIFT2
     
    private static final long
    SHIFT3
     
    private static final long
    SHIFT4
     

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
    BitUtil()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static long
    deinterleave(long b)
    Extract just the even-bits value as a long from the bit-interleaved value
    static long
    flipFlop(long b)
    flip flops odd with even bits
    static long
    interleave(int even, int odd)
    Interleaves the first 32 bits of each long value Adapted from: http://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN
    static int
    nextHighestPowerOfTwo(int v)
    returns the next highest power of two, or the current value if it's already a power of two or zero
    static long
    nextHighestPowerOfTwo(long v)
    returns the next highest power of two, or the current value if it's already a power of two or zero
    static long
    pop_andnot(long[] arr1, long[] arr2, int wordOffset, int numWords)
    Returns the popcount or cardinality of A & ~B.
    static long
    pop_array(long[] arr, int wordOffset, int numWords)
    Returns the number of set bits in an array of longs.
    static long
    pop_intersect(long[] arr1, long[] arr2, int wordOffset, int numWords)
    Returns the popcount or cardinality of the two sets after an intersection.
    static long
    pop_union(long[] arr1, long[] arr2, int wordOffset, int numWords)
    Returns the popcount or cardinality of the union of two sets.
    static long
    pop_xor(long[] arr1, long[] arr2, int wordOffset, int numWords)
    Returns the popcount or cardinality of A ^ B Neither array is modified.
    static int
    zigZagDecode(int i)
    Decode an int previously encoded with zigZagEncode(int).
    static long
    zigZagDecode(long l)
    Decode a long previously encoded with zigZagEncode(long).
    static int
    zigZagEncode(int i)
    Same as zigZagEncode(long) but on integers.
    static long
    zigZagEncode(long l)
    Zig-zag encode the provided long.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

  • Constructor Details

    • BitUtil

      private BitUtil()

  • Method Details

    • pop_array

      public static long pop_array(long[] arr, int wordOffset, int numWords)
      Returns the number of set bits in an array of longs.

    • pop_intersect

      public static long pop_intersect(long[] arr1, long[] arr2, int wordOffset, int numWords)
      Returns the popcount or cardinality of the two sets after an intersection. Neither array is modified.

    • pop_union

      public static long pop_union(long[] arr1, long[] arr2, int wordOffset, int numWords)
      Returns the popcount or cardinality of the union of two sets. Neither array is modified.

    • pop_andnot

      public static long pop_andnot(long[] arr1, long[] arr2, int wordOffset, int numWords)
      Returns the popcount or cardinality of A & ~B. Neither array is modified.

    • pop_xor

      public static long pop_xor(long[] arr1, long[] arr2, int wordOffset, int numWords)
      Returns the popcount or cardinality of A ^ B Neither array is modified.

    • nextHighestPowerOfTwo

      public static int nextHighestPowerOfTwo(int v)
      returns the next highest power of two, or the current value if it's already a power of two or zero

    • nextHighestPowerOfTwo

      public static long nextHighestPowerOfTwo(long v)
      returns the next highest power of two, or the current value if it's already a power of two or zero

    • interleave

      public static long interleave(int even, int odd)
      Interleaves the first 32 bits of each long value Adapted from: http://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN

    • deinterleave

      public static long deinterleave(long b)
      Extract just the even-bits value as a long from the bit-interleaved value

    • flipFlop

      public static long flipFlop(long b)
      flip flops odd with even bits

    • zigZagEncode

      public static int zigZagEncode(int i)
      Same as zigZagEncode(long) but on integers.

    • zigZagEncode

      public static long zigZagEncode(long l)
      Zig-zag encode the provided long. Assuming the input is a signed long whose absolute value can be stored on n bits, the returned value will be an unsigned long that can be stored on n+1 bits.

    • zigZagDecode

      public static int zigZagDecode(int i)
      Decode an int previously encoded with zigZagEncode(int).

    • zigZagDecode

      public static long zigZagDecode(long l)
      Decode a long previously encoded with zigZagEncode(long).