Package org.apache.lucene.util

Class BitUtil

  • public final class BitUtil
extends java.lang.Object
    A variety of high efficiency bit twiddling routines.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static int bitCount​(byte b)
      Return the number of bits sets in b.
      static int bitList​(byte b)
      Return the list of bits which are set in b encoded as followed: (i >>> (4 * n)) & 0x0F is the offset of the n-th set bit of the given byte plus one, or 0 if there are n or less bits set in the given byte.
      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.

      • Methods inherited from class java.lang.Object

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

    • Method Detail

      • bitCount

        public static int bitCount​(byte b)
        Return the number of bits sets in b.

      • bitList

        public static int bitList​(byte b)
        Return the list of bits which are set in b encoded as followed: (i >>> (4 * n)) & 0x0F is the offset of the n-th set bit of the given byte plus one, or 0 if there are n or less bits set in the given byte. For example bitList(12) returns 0x43:
        • 0x43 & 0x0F is 3, meaning the the first bit set is at offset 3-1 = 2,
        • (0x43 >>> 4) & 0x0F is 4, meaning there is a second bit set at offset 4-1=3,
        • (0x43 >>> 8) & 0x0F is 0, meaning there is no more bit set in this byte.

      • 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