Class JenkinsHash


  • public class JenkinsHash
    extends Object
    • Constructor Detail

      • JenkinsHash

        public JenkinsHash()
    • Method Detail

      • getInstance

        public static JenkinsHash getInstance()
      • 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 seed of -1.
        Parameters:
        bytes - input bytes
        Returns:
        hash value
      • hash

        public int hash​(byte[] key,
                        int nbytes,
                        int initval)
        taken from hashlittle() -- hash a variable-length key into a 32-bit value
        Parameters:
        key - the key (the unaligned variable-length array of bytes)
        nbytes - number of bytes to include in hash
        initval - can be any integer value
        Returns:
        a 32-bit value. Every bit of the key affects every bit of the return value. Two keys differing by one or two bits will have totally different hash values.

        The best hash table sizes are powers of 2. There is no need to do mod a prime (mod is sooo slow!). If you need less than 32 bits, use a bitmask. For example, if you need only 10 bits, do h = (h & hashmask(10)); In which case, the hash table should have hashsize(10) elements.

        If you are hashing n strings byte[][] k, do it like this: for (int i = 0, h = 0; i < n; ++i) h = hash( k[i], h);

        By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this code any way you wish, private, educational, or commercial. It's free.

        Use for hash table lookup, or anything where one collision in 2^^32 is acceptable. Do NOT use for cryptographic purposes.