org.apache.datasketches.memory

Class XxHash

java.lang.Object

org.apache.datasketches.memory.XxHash

public final class XxHash
extends Object

The XxHash is a fast, non-cryptographic, 64-bit hash function that has excellent avalanche and 2-way bit independence properties. This java version adapted the C++ version and the OpenHFT/Zero-Allocation-Hashing implementation referenced below as inspiration.

The C++ source repository: https://github.com/Cyan4973/xxHash. It has a BSD 2-Clause License: http://www.opensource.org/licenses/bsd-license.php. See LICENSE.

Portions of this code were adapted from OpenHFT/Zero-Allocation-Hashing, which has an Apache 2 license as does this site. See LICENSE.

Author:

Lee Rhodes

Method Summary

Modifier and Type	Method and Description
static long	hashByteArr(byte[] arr, long offsetBytes, long lengthBytes, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashCharArr(char[] arr, long offsetChars, long lengthChars, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashDoubleArr(double[] arr, long offsetDoubles, long lengthDoubles, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashFloatArr(float[] arr, long offsetFloats, long lengthFloats, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashIntArr(int[] arr, long offsetInts, long lengthInts, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashLong(long in, long seed) Returns a 64-bit hash from a single long.
static long	hashLongArr(long[] arr, long offsetLongs, long lengthLongs, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashShortArr(short[] arr, long offsetShorts, long lengthShorts, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.
static long	hashString(String str, long offsetChars, long lengthChars, long seed) Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Methods inherited from class java.lang.Object

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

Method Detail

hashByteArr

public static long hashByteArr(byte[] arr,
                               long offsetBytes,
                               long lengthBytes,
                               long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetBytes - starting at this offset

lengthBytes - continuing for this length

seed - the given seed

Returns:

the hash

hashShortArr

public static long hashShortArr(short[] arr,
                                long offsetShorts,
                                long lengthShorts,
                                long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetShorts - starting at this offset

lengthShorts - continuing for this length

seed - the given seed

Returns:

the hash

hashCharArr

public static long hashCharArr(char[] arr,
                               long offsetChars,
                               long lengthChars,
                               long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetChars - starting at this offset

lengthChars - continuing for this length

seed - the given seed

Returns:

the hash

hashIntArr

public static long hashIntArr(int[] arr,
                              long offsetInts,
                              long lengthInts,
                              long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetInts - starting at this offset

lengthInts - continuing for this length

seed - the given seed

Returns:

the hash

hashLongArr

public static long hashLongArr(long[] arr,
                               long offsetLongs,
                               long lengthLongs,
                               long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetLongs - starting at this offset

lengthLongs - continuing for this length

seed - the given seed

Returns:

the hash

hashLong

public static long hashLong(long in,
                            long seed)

Returns a 64-bit hash from a single long. This method has been optimized for speed when only a single hash of a long is required.

Parameters:

in - A long.

seed - A long valued seed.

Returns:

the hash.

hashFloatArr

public static long hashFloatArr(float[] arr,
                                long offsetFloats,
                                long lengthFloats,
                                long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetFloats - starting at this offset

lengthFloats - continuing for this length

seed - the given seed

Returns:

the hash

hashDoubleArr

public static long hashDoubleArr(double[] arr,
                                 long offsetDoubles,
                                 long lengthDoubles,
                                 long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

arr - the given array

offsetDoubles - starting at this offset

lengthDoubles - continuing for this length

seed - the given seed

Returns:

the hash

hashString

public static long hashString(String str,
                              long offsetChars,
                              long lengthChars,
                              long seed)

Hash the given arr starting at the given offset and continuing for the given length using the given seed.

Parameters:

str - the given string

offsetChars - starting at this offset

lengthChars - continuing for this length

seed - the given seed

Returns:

the hash