java.lang.Object
- org.apache.lucene.util.BitUtil

```
public final class BitUtil
extends Object
```
A variety of high efficiency bit twiddling routines.

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

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static int`	`countBits(long[] bits, int numLongs)`	Counts all bits set in the provided longs.
`static int`	`countBitsUpTo(long[] bits, int numLongs, int bitIndex)`	Counts the bits set up to the given bit zero-based index, exclusive.
`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 boolean`	`isBitSet(long[] bits, int numLongs, int bitIndex)`	Returns whether the bit at given zero-based index is set.
`static int`	`nextBitSet(long[] bits, int numLongs, int bitIndex)`	Returns the index of the next bit set following the given bit zero-based index.
`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`	`previousBitSet(long[] bits, int numLongs, int bitIndex)`	Returns the index of the previous bit set preceding the given bit zero-based index.
`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

- Method Detail
  - 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 final 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).
  - isBitSet
```
public static boolean isBitSet(long[] bits,
                               int numLongs,
                               int bitIndex)
```
    Returns whether the bit at given zero-based index is set.
    Example: bitIndex 66 means the third bit on the right of the second long.
    
    Parameters:
    
    bits - The bits stored in an array of long for efficiency.
    
    numLongs - The number of longs in bits to consider.
    
    bitIndex - The bit zero-based index. It must be greater than or equal to 0, and strictly less than numLongs * Long.SIZE.
  - countBits
```
public static int countBits(long[] bits,
                            int numLongs)
```
    Counts all bits set in the provided longs.
    
    Parameters:
    
    bits - The bits stored in an array of long for efficiency.
    
    numLongs - The number of longs in bits to consider.
  - countBitsUpTo
```
public static int countBitsUpTo(long[] bits,
                                int numLongs,
                                int bitIndex)
```
    Counts the bits set up to the given bit zero-based index, exclusive.
    In other words, how many 1s there are up to the bit at the given index excluded.
    Example: bitIndex 66 means the third bit on the right of the second long.
    
    Parameters:
    
    bits - The bits stored in an array of long for efficiency.
    
    numLongs - The number of longs in bits to consider.
    
    bitIndex - The bit zero-based index, exclusive. It must be greater than or equal to 0, and less than or equal to numLongs * Long.SIZE.
  - nextBitSet
```
public static int nextBitSet(long[] bits,
                             int numLongs,
                             int bitIndex)
```
    Returns the index of the next bit set following the given bit zero-based index.
    For example with bits 100011: the next bit set after index=-1 is at index=0; the next bit set after index=0 is at index=1; the next bit set after index=1 is at index=5; there is no next bit set after index=5.
    
    Parameters:
    
    bits - The bits stored in an array of long for efficiency.
    
    numLongs - The number of longs in bits to consider.
    
    bitIndex - The bit zero-based index. It must be greater than or equal to -1, and strictly less than numLongs * Long.SIZE.
    
    Returns:
    
    The zero-based index of the next bit set after the provided bitIndex; or -1 if none.
  - previousBitSet
```
public static int previousBitSet(long[] bits,
                                 int numLongs,
                                 int bitIndex)
```
    Returns the index of the previous bit set preceding the given bit zero-based index.
    For example with bits 100011: there is no previous bit set before index=0. the previous bit set before index=1 is at index=0; the previous bit set before index=5 is at index=1; the previous bit set before index=64 is at index=5;
    
    Parameters:
    
    bits - The bits stored in an array of long for efficiency.
    
    numLongs - The number of longs in bits to consider.
    
    bitIndex - The bit zero-based index. It must be greater than or equal to 0, and less than or equal to numLongs * Long.SIZE.
    
    Returns:
    
    The zero-based index of the previous bit set before the provided bitIndex; or -1 if none.

Class BitUtil

Method Summary

Methods inherited from class java.lang.Object

Method Detail

pop_array

pop_intersect

pop_union

pop_andnot

pop_xor

nextHighestPowerOfTwo

nextHighestPowerOfTwo

interleave

deinterleave

flipFlop

zigZagEncode

zigZagEncode

zigZagDecode

zigZagDecode

isBitSet

countBits

countBitsUpTo

nextBitSet

previousBitSet