Module datarush.commons
Package com.pervasive.datarush.commons.util

Class HashUtil

java.lang.Object
com.pervasive.datarush.commons.util.HashUtil
public final class HashUtil extends Object
Utility methods for hashing different data types.

These hashes are based on C code placed in the public domain by Bob Jenkins. They are advertised as strong enough to allow the use of hash & mask instead of hash % prime for computing a hash bucket.

  • Field Details

    • NULL_HASH_CODE

      public static final int NULL_HASH_CODE
      An arbitrary nonzero constant for the hash code of null valued tokens.
      See Also:

  • Constructor Details

    • HashUtil

      public HashUtil()

  • Method Details

    • binaryHashCode

      public static final int binaryHashCode(byte[] bytes)
      Hash a binary value using Bob Jenkins' "One-at-a-Time Hash".
      Parameters:
      bytes - the value to hash
      Returns:
      the hash code

    • binaryHashCode

      public static final int binaryHashCode(byte[] bytes, int offset, int len)
      Hash a binary value using Bob Jenkins' "One-at-a-Time Hash".
      Parameters:
      bytes - the value to hash
      offset - start offset
      len - number of bytes to code
      Returns:
      the hash code

    • intHashCode

      public static final int intHashCode(int a)
      Hash a binary value using Bob Jenkins' "4-byte Integer Hashing".
      Parameters:
      a - the value to hash
      Returns:
      the hash code

    • charHashCode

      public static final int charHashCode(char c)
      Hashes a character value using the same algorithm as intHashCode(int).
      Parameters:
      c - the value to hash
      Returns:
      the hash code

    • booleanHashCode

      public static final int booleanHashCode(boolean b)
      Hashes a boolean value using the same algorithm as intHashCode(int).
      Parameters:
      b - the value to hash
      Returns:
      the hash code

    • doubleHashCode

      public static final int doubleHashCode(double d)
      Hashes a double value using the same algorithm as longHashCode(long).
      Parameters:
      d - the value to hash
      Returns:
      the hash code

    • floatHashCode

      public static final int floatHashCode(float f)
      Hashes a float value using the same algorithm as intHashCode(int).
      Parameters:
      f - the value to hash
      Returns:
      the hash code

    • longHashCode

      public static final int longHashCode(long l)
      Hashes a long value.
      Parameters:
      l - the value to hash
      Returns:
      the hash code

    • objectHashCode

      public static final int objectHashCode(Object o)
      Hashes an object using Object.hashCode(). Null values are given their own hash code.
      Parameters:
      o - the value to hash
      Returns:
      the hash code

    • timestampHashCode

      public static final int timestampHashCode(long epochSecs, int nanos)
      Hashes a timestamp decomposed in seconds and nanos parts. Note that time zone offset is deliberately not included. Equal timestamp values in different time zones must have the same hashCode.
      Parameters:
      epochSecs - the seconds-since-epoch portion of the timestamp
      nanos - the nanoseconds portion of the timestamp
      Returns:
      the hash code

    • finalMix

      public static final int finalMix(int a, int b, int c)
      Replicates the computation of Bob Jenkins' "final" macro.
      Parameters:
      a - the first input to the macro
      b - the second input to the macro
      c - the third input to the macro
      Returns:
      the resulting mix