org.jau.util.BitMath Class Reference

Collaboration diagram for org.jau.util.BitMath:

Static Public Member Functions
static int	getBitMask (final int n)
	Returns the 32 bit mask of n-bits, i.e. More...
static final int	bitCount (int n)
	Returns the number of set bits within given 32bit integer in O(1) using a HAKEM 169 Bit Count inspired implementation: More...
static final boolean	isPowerOf2 (final int n)
	Returns true if the given integer is a power of 2. More...
static final int	nextPowerOf2 (int n)
	Returns the next higher power of 2 of 32-bit of given n @endiliteral. More...
static final int	roundToPowerOf2 (final int n)
	If the given n is not isPowerOf2(int) return nextPowerOf2(int), otherwise return n unchanged. More...

Static Public Attributes
static final int	UNSIGNED_INT_MAX_VALUE = 0xffffffff
	Maximum 32 bit Unsigned Integer Value: 0xffffffff == {@value}. More...
static final int	MAX_POWER_OF_2 = 1 << ( Integer.SIZE - 2 )
	Maximum 32bit integer value being of isPowerOf2(int). More...

Detailed Description

Definition at line 26 of file BitMath.java.

Member Function Documentation

bitCount()

static final int org.jau.util.BitMath.bitCount ( int  n )

static

Returns the number of set bits within given 32bit integer in O(1) using a HAKEM 169 Bit Count inspired implementation:

  http://www.inwap.com/pdp10/hbaker/hakmem/hakmem.html
  http://home.pipeline.com/~hbaker1/hakmem/hacks.html#item169
  http://tekpool.wordpress.com/category/bit-count/
  http://www.hackersdelight.org/

<p<blockquote>‍

We rely on the JVM spec Integer#SIZE == 32.

Definition at line 68 of file BitMath.java.

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getBitMask()

static int org.jau.util.BitMath.getBitMask ( final int  n )

static

Returns the 32 bit mask of n-bits, i.e.

n low order 1's.

Implementation handles n == 32.

Exceptions

IndexOutOfBoundsException

if b is out of bounds, i.e. > 32

Definition at line 45 of file BitMath.java.

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isPowerOf2()

static final boolean org.jau.util.BitMath.isPowerOf2 ( final int  n )

static

Returns true if the given integer is a power of 2.

Source: bithacks: http://www.graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2

Definition at line 94 of file BitMath.java.

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nextPowerOf2()

static final int org.jau.util.BitMath.nextPowerOf2 ( int  n )

static

Returns the next higher power of 2 of 32-bit of given n @endiliteral.


Source: bithacks: http://www.graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2

We rely on the JVM spec Integer#SIZE == 32.

Definition at line 107 of file BitMath.java.

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roundToPowerOf2()

static final int org.jau.util.BitMath.roundToPowerOf2 ( final int  n )

static

If the given n is not isPowerOf2(int) return nextPowerOf2(int), otherwise return n unchanged.

return isPowerOf2(n) ? n : nextPowerOf2(n);

<p<blockquote>‍

We rely on the JVM spec Integer#SIZE == 32.

Definition at line 127 of file BitMath.java.

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Member Data Documentation

MAX_POWER_OF_2

final int org.jau.util.BitMath.MAX_POWER_OF_2 = 1 << ( Integer.SIZE - 2 )

static

Maximum 32bit integer value being of isPowerOf2(int).

We rely on the JVM spec Integer#SIZE == 32.

Definition at line 36 of file BitMath.java.

UNSIGNED_INT_MAX_VALUE

final int org.jau.util.BitMath.UNSIGNED_INT_MAX_VALUE = 0xffffffff

static

Maximum 32 bit Unsigned Integer Value: 0xffffffff == {@value}.

Definition at line 28 of file BitMath.java.

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The documentation for this class was generated from the following file:

• java_base/org/jau/util/BitMath.java