net.jpountz.xxhash.XXHashFactory Maven / Gradle / Ivy
package net.jpountz.xxhash;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.Random;
/**
* Entry point to get {@link XXHash32} and {@link StreamingXXHash32} instances.
*/
public final class XXHashFactory {
private static XXHashFactory instance(String impl) {
try {
return new XXHashFactory(impl);
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
}
}
/** Return a {@link XXHashFactory} that returns {@link XXHash32} instances that
* are native bindings to the original C API. */
public static XXHashFactory nativeInstance() {
return instance("JNI");
}
/** Return a {@link XXHashFactory} that returns {@link XXHash32} instances that
* are written with Java's official API. */
public static XXHashFactory safeInstance() {
return instance("JavaSafe");
}
/** Return a {@link XXHashFactory} that returns {@link XXHash32} instances that
* may use {@link sun.misc.Unsafe} to speed up hashing. */
public static XXHashFactory unsafeInstance() {
return instance("JavaUnsafe");
}
/**
* Return the fastest available {@link XXHashFactory} instance. This method
* will first try to load the native instance, then the unsafe java one and
* finally the safe java one if the JVM doesn't have {@link sun.misc.Unsafe}
* support.
*/
public static XXHashFactory fastestInstance() {
try {
return nativeInstance();
} catch (Throwable t1) {
try {
return unsafeInstance();
} catch (Throwable t2) {
return safeInstance();
}
}
}
private final String impl;
private final XXHash32 hash32;
private final StreamingXXHash32Factory streamingHash32Factory;
private XXHashFactory(String impl) throws ClassNotFoundException {
this.impl = impl;
final Class xxHashEnum = Class.forName(XXHash32.class.getName() + impl);
if (!XXHash32.class.isAssignableFrom(xxHashEnum)) {
throw new AssertionError();
}
@SuppressWarnings("unchecked")
XXHash32[] xxHashs32 = ((Class) xxHashEnum).getEnumConstants();
if (xxHashs32.length != 1) {
throw new AssertionError();
}
this.hash32 = xxHashs32[0];
final Class streamingXXHashFactoryEnum = Class.forName(StreamingXXHash32Factory.class.getName() + impl);
if (!StreamingXXHash32Factory.class.isAssignableFrom(streamingXXHashFactoryEnum)) {
throw new AssertionError();
}
@SuppressWarnings("unchecked")
StreamingXXHash32Factory[] streamingXXHash32Factories = ((Class) streamingXXHashFactoryEnum).getEnumConstants();
if (streamingXXHash32Factories.length != 1) {
throw new AssertionError();
}
this.streamingHash32Factory = streamingXXHash32Factories[0];
// make sure it can run
final byte[] bytes = new byte[100];
final Random random = new Random();
random.nextBytes(bytes);
final int seed = random.nextInt();
final int h1 = hash32.hash(bytes, 0, bytes.length, seed);
final StreamingXXHash32 streamingHash32 = newStreamingHash32(seed);
streamingHash32.update(bytes, 0, bytes.length);
final int h2 = streamingHash32.getValue();
if (h1 != h2) {
throw new AssertionError();
}
}
/** Return a {@link XXHash32} instance. */
public XXHash32 hash32() {
return hash32;
}
/**
* Return a new {@link StreamingXXHash32} instance.
*/
public StreamingXXHash32 newStreamingHash32(int seed) {
return streamingHash32Factory.newStreamingHash(seed);
}
/** Prints the fastest instance. */
public static void main(String[] args) {
System.out.println("Fastest instance is " + fastestInstance());
}
@Override
public String toString() {
return getClass().getSimpleName() + ":" + impl;
}
}