Package org.h2.util

Class MathUtils

  • public class MathUtils
extends java.lang.Object
    This is a utility class with mathematical helper functions.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method 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