LZ4 and xxHash 1.3.0 · net.jpountz.xxhash.XXHashFactory

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 sun.misc.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.

Field Summary

Modifier and Type	Field and Description
private final XXHash32	hash32
private final XXHash64	hash64
private final String	impl
private static XXHashFactory	JAVA_SAFE_INSTANCE
private static XXHashFactory	JAVA_UNSAFE_INSTANCE
private static XXHashFactory	NATIVE_INSTANCE
private final StreamingXXHash32.Factory	streamingHash32Factory
private final StreamingXXHash64.Factory	streamingHash64Factory

Constructor Summary

Access	Constructor and Description
private	XXHashFactory(String impl)

Method Summary

Modifier and Type	Method and Description
private static <T> T	classInstance(String cls)
public static XXHashFactory	fastestInstance() Return the fastest available `XXHashFactory` instance.
public static XXHashFactory	fastestJavaInstance() Return the fastest available `XXHashFactory` instance which does not rely on JNI bindings.
public XXHash32	hash32() Return a `XXHash32` instance.
public XXHash64	hash64() Return a `XXHash64` instance.
private static XXHashFactory	instance(String impl)
public static void	main(String[] args) Prints the fastest instance.
public static synchronized XXHashFactory	nativeInstance() Return a `XXHashFactory` that returns `XXHash32` instances that are native bindings to the original C API.
public StreamingXXHash32	newStreamingHash32(int seed) Return a new `StreamingXXHash32` instance.
public StreamingXXHash64	newStreamingHash64(long seed) Return a new `StreamingXXHash64` instance.
public static synchronized XXHashFactory	safeInstance() Return a `XXHashFactory` that returns `XXHash32` instances that are written with Java's official API.
public String	toString() Overrides java.lang.Object.toString. Returns a string representation of the object.
public static synchronized XXHashFactory	unsafeInstance() Return a `XXHashFactory` that returns `XXHash32` instances that may use `sun.misc.Unsafe` to speed up hashing.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll wait wait wait

Field Detail

hash32	back to summary
private final XXHash32 hash32

hash64	back to summary
private final XXHash64 hash64

impl	back to summary
private final String impl

JAVA_SAFE_INSTANCE	back to summary
private static XXHashFactory JAVA_SAFE_INSTANCE

JAVA_UNSAFE_INSTANCE	back to summary
private static XXHashFactory JAVA_UNSAFE_INSTANCE

NATIVE_INSTANCE	back to summary
private static XXHashFactory NATIVE_INSTANCE

streamingHash32Factory	back to summary
private final StreamingXXHash32.Factory streamingHash32Factory

streamingHash64Factory	back to summary
private final StreamingXXHash64.Factory streamingHash64Factory

Constructor Detail

XXHashFactory	back to summary
private XXHashFactory(String impl) throws ClassNotFoundException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException

Method Detail

classInstance	back to summary
private static <T> T classInstance(String cls) throws NoSuchFieldException, SecurityException, ClassNotFoundException, IllegalArgumentException, IllegalAccessException Annotations @SuppressWarnings:unchecked

fastestInstance back to summary

fastestInstance	back to summary
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.

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.

fastestJavaInstance	back to summary
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 `sun.misc.Unsafe`.

hash32	back to summary
public XXHash32 hash32() Return a `XXHash32` instance.

hash64	back to summary
public XXHash64 hash64() Return a `XXHash64` instance.

instance	back to summary
private static XXHashFactory instance(String impl)

main	back to summary
public static void main(String[] args) Prints the fastest instance.

nativeInstance back to summary

nativeInstance	back to summary
public static synchronized 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: 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. 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.

public static synchronized 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:

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.
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.

newStreamingHash32	back to summary
public StreamingXXHash32 newStreamingHash32(int seed) Return a new `StreamingXXHash32` instance.

newStreamingHash64	back to summary
public StreamingXXHash64 newStreamingHash64(long seed) Return a new `StreamingXXHash64` instance.

safeInstance	back to summary
public static synchronized XXHashFactory safeInstance() Return a `XXHashFactory` that returns `XXHash32` instances that are written with Java's official API.

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Doc from java.lang.Object.toString. Returns a string representation of the object. Returns:String a string representation of the object. Annotations @Override

toString

back to summary

public String toString()

Overrides java.lang.Object.toString.

Doc from java.lang.Object.toString.

Returns a string representation of the object.

Returns:String

a string representation of the object.

Annotations

@Override