net.jpountz.xxhash

Class XXHashFactory

java.lang.Object

net.jpountz.xxhash.XXHashFactory

public final class XXHashFactory
extends java.lang.Object

Entry point to get XXHash32 and StreamingXXHash32 instances.

This class has 3 instances

• a native instance which is a JNI binding to the original LZ4 C implementation.
• a safe Java instance which is a pure Java port of the original C library,
• an unsafe Java instance which is a Java port using the unofficial Unsafe API.

Only the safe instance is guaranteed to work on your JVM, as a consequence it is advised to use the fastestInstance() or fastestJavaInstance() to pull a XXHashFactory instance.

All methods from this class are very costly, so you should get an instance once, and then reuse it whenever possible. This is typically done by storing a XXHashFactory instance in a static field.

Method Summary

Modifier and Type	Method and Description
static XXHashFactory	fastestInstance() Return the fastest available XXHashFactory instance.
static XXHashFactory	fastestJavaInstance() Return the fastest available XXHashFactory instance which does not rely on JNI bindings.
XXHash32	hash32() Return a XXHash32 instance.
XXHash64	hash64() Return a XXHash64 instance.
static void	main(java.lang.String[] args) Prints the fastest instance.
static XXHashFactory	nativeInstance() Return a XXHashFactory that returns XXHash32 instances that are native bindings to the original C API.
StreamingXXHash32	newStreamingHash32(int seed) Return a new StreamingXXHash32 instance.
StreamingXXHash64	newStreamingHash64(long seed) Return a new StreamingXXHash64 instance.
static XXHashFactory	safeInstance() Return a XXHashFactory that returns XXHash32 instances that are written with Java's official API.
java.lang.String	toString()
static XXHashFactory	unsafeInstance() Return a XXHashFactory that returns XXHash32 instances that may use Unsafe to speed up hashing.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

nativeInstance

public static XXHashFactory nativeInstance()

Return a XXHashFactory that returns XXHash32 instances that are native bindings to the original C API.

Please note that this instance has some traps you should be aware of:

1. Upon loading this instance, files will be written to the temporary directory of the system. Although these files are supposed to be deleted when the JVM exits, they might remain on systems that don't support removal of files being used such as Windows.
2. The instance can only be loaded once per JVM. This can be a problem if your application uses multiple class loaders (such as most servlet containers): this instance will only be available to the children of the class loader which has loaded it. As a consequence, it is advised to either not use this instance in webapps or to put this library in the lib directory of your servlet container so that it is loaded by the system class loader.

safeInstance

public static XXHashFactory safeInstance()

Return a XXHashFactory that returns XXHash32 instances that are written with Java's official API.

unsafeInstance

public static XXHashFactory unsafeInstance()

Return a XXHashFactory that returns XXHash32 instances that may use Unsafe to speed up hashing.

fastestJavaInstance

public static XXHashFactory fastestJavaInstance()

Return the fastest available XXHashFactory instance which does not rely on JNI bindings. It first tries to load the unsafe instance, and then the safe Java instance if the JVM doesn't have a working Unsafe.

fastestInstance

public static XXHashFactory fastestInstance()

Return the fastest available XXHashFactory instance. If the class loader is the system class loader and if the native instance loads successfully, then the native instance is returned, otherwise the fastest Java instance is returned.

Please read javadocs of nativeInstance() before using this method.

hash32

public XXHash32 hash32()

Return a XXHash32 instance.

hash64

public XXHash64 hash64()

Return a XXHash64 instance.

newStreamingHash32

public StreamingXXHash32 newStreamingHash32(int seed)

Return a new StreamingXXHash32 instance.

newStreamingHash64

public StreamingXXHash64 newStreamingHash64(long seed)

Return a new StreamingXXHash64 instance.

main

public static void main(java.lang.String[] args)

Prints the fastest instance.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object