Package org.apache.hadoop.util.hash

Class Hash

java.lang.Object
org.apache.hadoop.util.hash.Hash
Direct Known Subclasses:
JenkinsHash, MurmurHash
@Private @Unstable public abstract class Hash extends Object
This class represents a common API for hashing functions.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    INVALID_HASH
    Constant to denote invalid hash type.
    static final int
    JENKINS_HASH
    Constant to denote JenkinsHash.
    static final int
    MURMUR_HASH
    Constant to denote MurmurHash.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Hash()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static int
    getHashType(Configuration conf)
    This utility method converts the name of the configured hash type to a symbolic constant.
    static Hash
    getInstance(int type)
    Get a singleton instance of hash function of a given type.
    static Hash
    getInstance(Configuration conf)
    Get a singleton instance of hash function of a type defined in the configuration.
    int
    hash(byte[] bytes)
    Calculate a hash using all bytes from the input argument, and a seed of -1.
    int
    hash(byte[] bytes, int initval)
    Calculate a hash using all bytes from the input argument, and a provided seed value.
    abstract int
    hash(byte[] bytes, int length, int initval)
    Calculate a hash using bytes from 0 to length, and the provided seed value
    static int
    parseHashType(String name)
    This utility method converts String representation of hash function name to a symbolic constant.

    Methods inherited from class java.lang.Object

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

  • Field Details

  • Constructor Details

    • Hash

      public Hash()

  • Method Details

    • parseHashType

      public static int parseHashType(String name)
      This utility method converts String representation of hash function name to a symbolic constant. Currently two function types are supported, "jenkins" and "murmur".
      Parameters:
      name - hash function name
      Returns:
      one of the predefined constants

    • getHashType

      public static int getHashType(Configuration conf)
      This utility method converts the name of the configured hash type to a symbolic constant.
      Parameters:
      conf - configuration
      Returns:
      one of the predefined constants

    • getInstance

      public static Hash getInstance(int type)
      Get a singleton instance of hash function of a given type.
      Parameters:
      type - predefined hash type
      Returns:
      hash function instance, or null if type is invalid

    • getInstance

      public static Hash getInstance(Configuration conf)
      Get a singleton instance of hash function of a type defined in the configuration.
      Parameters:
      conf - current configuration
      Returns:
      defined hash type, or null if type is invalid

    • hash

      public int hash(byte[] bytes)
      Calculate a hash using all bytes from the input argument, and a seed of -1.
      Parameters:
      bytes - input bytes
      Returns:
      hash value

    • hash

      public int hash(byte[] bytes, int initval)
      Calculate a hash using all bytes from the input argument, and a provided seed value.
      Parameters:
      bytes - input bytes
      initval - seed value
      Returns:
      hash value

    • hash

      public abstract int hash(byte[] bytes, int length, int initval)
      Calculate a hash using bytes from 0 to length, and the provided seed value
      Parameters:
      bytes - input bytes
      length - length of the valid bytes to consider
      initval - seed value
      Returns:
      hash value