Package convex.core.util

Class Bits

java.lang.Object

convex.core.util.Bits

public class Bits
extends Object

Static utility function for bitwise functions

Constructor Summary

Constructors

Constructor	Description
Bits()

Method Summary

Modifier and Type	Method	Description
static final int	hash32(long x)	32-bit salted hash function for hashtables etc.
static final long	hash64(long x)	64-bit salted hash function for hashtables etc.
static int	indexForDigit(int digit, short mask)	Returns the index from the present mask for the given hex digit (0-15), or -1 if not found
static int	leadingOnes(long value)
static int	leadingZeros(int x)	Get the number of leading zeros in the binary representation of an int
static int	leadingZeros(long x)	Get the number of leading zeros in the binary representation of a long
static int	lowBitMask(int numBits)	Gets a bit mask for the specified number of low bits in an int
static int	lowBits(int numBits, int val)	Gets the specified number of low Bits in an integer.
static int	positionForDigit(int digit, short mask)	Returns the array position for a given digit given a current mask.
static long	xorshift64(long x)	Compute XORShift64 PRNG for a given value

Methods inherited from class java.lang.Object

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

Constructor Details

Bits

public Bits()

Method Details

indexForDigit

public static int indexForDigit(int digit,
 short mask)

Returns the index from the present mask for the given hex digit (0-15), or -1 if not found

Parameters:

digit - Hex digit (0-15)

mask - Bitmask of hex digits

Returns:

The index of the appropriate child for this digit, or -1 if not found

positionForDigit

public static int positionForDigit(int digit,
 short mask)

Returns the array position for a given digit given a current mask. If not present, this is where the new array entry must be inserted.

Parameters:

digit - Hex digit (0-15)

mask - Bitmask of hex digits

Returns:

Array position for the given digit in the specified mask

leadingZeros

public static int leadingZeros(int x)

Get the number of leading zeros in the binary representation of an int

Parameters:

x - int value to check

Returns:

Number of leading zeros (0-32)

leadingZeros

public static int leadingZeros(long x)

Get the number of leading zeros in the binary representation of a long

Parameters:

x - long value to check

Returns:

Number of leading zeros (0-64)

lowBitMask

public static int lowBitMask(int numBits)

Gets a bit mask for the specified number of low bits in an int

Parameters:

numBits - Number of bits to set to 1

Returns:

int containing the specified number of set low bits

lowBits

public static int lowBits(int numBits,
 int val)

Gets the specified number of low Bits in an integer. Other bits are zeroed.

Parameters:

numBits - Number of bits to get

val - Value to extract bits from

Returns:

Masked in with the specified number of low bits

leadingOnes

public static int leadingOnes(long value)

xorshift64

public static long xorshift64(long x)

Compute XORShift64 PRNG for a given value

Parameters:

x - Input value (state)

Returns:

PRNG value for x

hash64

public static final long hash64(long x)

64-bit salted hash function for hashtables etc.

Returns:

Hash value using salted hash

hash32

public static final int hash32(long x)

32-bit salted hash function for hashtables etc.

Returns:

Hash value using salted hash