org.h2.util

Class MathUtils

java.lang.Object

org.h2.util.MathUtils

public class MathUtils
extends java.lang.Object

This is a utility class with mathematical helper functions.

Method Summary

Modifier and Type	Method and Description
static short	convertIntToShort(int i) Convert an int value to a short value.
static int	convertLongToInt(long l) Convert a long value to an int value.
static byte[]	generateAlternativeSeed() Generate a seed value, using as much unpredictable data as possible.
static int	nextPowerOf2(int x) Get the value that is equal to or higher than this value, and that is a power of two.
static void	randomBytes(byte[] bytes) Get a number of pseudo random bytes.
static int	randomInt(int lowerThan) Get a pseudo random int value between 0 (including and the given value (excluding).
static int	roundUpInt(int x, int blockSizePowerOf2) Round the value up to the next block size.
static long	roundUpLong(long x, long blockSizePowerOf2) Round the value up to the next block size.
static byte[]	secureRandomBytes(int len) Get a number of cryptographically secure pseudo random bytes.
static int	secureRandomInt(int lowerThan) Get a cryptographically secure pseudo random int value between 0 (including and the given value (excluding).
static long	secureRandomLong() Get a cryptographically secure pseudo random long value.

Methods inherited from class java.lang.Object

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

Method Detail

roundUpInt

public static int roundUpInt(int x,
                             int blockSizePowerOf2)

Round the value up to the next block size. The block size must be a power of two. As an example, using the block size of 8, the following rounding operations are done: 0 stays 0; values 1..8 results in 8, 9..16 results in 16, and so on.

Parameters:

x - the value to be rounded

blockSizePowerOf2 - the block size

Returns:

the rounded value

roundUpLong

public static long roundUpLong(long x,
                               long blockSizePowerOf2)

Round the value up to the next block size. The block size must be a power of two. As an example, using the block size of 8, the following rounding operations are done: 0 stays 0; values 1..8 results in 8, 9..16 results in 16, and so on.

Parameters:

x - the value to be rounded

blockSizePowerOf2 - the block size

Returns:

the rounded value

generateAlternativeSeed

public static byte[] generateAlternativeSeed()

Generate a seed value, using as much unpredictable data as possible.

Returns:

the seed

nextPowerOf2

public static int nextPowerOf2(int x)
                        throws java.lang.IllegalArgumentException

Get the value that is equal to or higher than this value, and that is a power of two.

Parameters:

x - the original value

Returns:

the next power of two value

Throws:

java.lang.IllegalArgumentException - if x < 0 or x > 0x40000000

convertLongToInt

public static int convertLongToInt(long l)

Convert a long value to an int value. Values larger than the biggest int value are converted to the biggest int value, and values smaller than the smallest int value are converted to the smallest int value.

Parameters:

l - the value to convert

Returns:

the converted int value

convertIntToShort

public static short convertIntToShort(int i)

Convert an int value to a short value. Values larger than the biggest short value are converted to the biggest short value, and values smaller than the smallest short value are converted to the smallest short value.

Parameters:

i - the value to convert

Returns:

the converted short value

secureRandomLong

public static long secureRandomLong()

Get a cryptographically secure pseudo random long value.

Returns:

the random long value

randomBytes

public static void randomBytes(byte[] bytes)

Get a number of pseudo random bytes.

Parameters:

bytes - the target array

secureRandomBytes

public static byte[] secureRandomBytes(int len)

Get a number of cryptographically secure pseudo random bytes.

Parameters:

len - the number of bytes

Returns:

the random bytes

randomInt

public static int randomInt(int lowerThan)

Get a pseudo random int value between 0 (including and the given value (excluding). The value is not cryptographically secure.

Parameters:

lowerThan - the value returned will be lower than this value

Returns:

the random long value

secureRandomInt

public static int secureRandomInt(int lowerThan)

Get a cryptographically secure pseudo random int value between 0 (including and the given value (excluding).

Parameters:

lowerThan - the value returned will be lower than this value

Returns:

the random long value