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/*
* #%L
* ImgLib2: a general-purpose, multidimensional image processing library.
* %%
* Copyright (C) 2009 - 2018 Tobias Pietzsch, Stephan Preibisch, Stephan Saalfeld,
* John Bogovic, Albert Cardona, Barry DeZonia, Christian Dietz, Jan Funke,
* Aivar Grislis, Jonathan Hale, Grant Harris, Stefan Helfrich, Mark Hiner,
* Martin Horn, Steffen Jaensch, Lee Kamentsky, Larry Lindsey, Melissa Linkert,
* Mark Longair, Brian Northan, Nick Perry, Curtis Rueden, Johannes Schindelin,
* Jean-Yves Tinevez and Michael Zinsmaier.
* %%
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
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* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
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package net.imglib2.loops;
import java.lang.reflect.Constructor;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Stream;
/**
* Helper to create multiple copies of a class.
*
* The copies of the class have individual copies of the byte code.
* The JIT compiler optimizes the class copies individually,
* which can increase performance.
*
* @author Matthias Arzt
*/
public class ClassCopyProvider< T >
{
private final Map< Object, Class< ? extends T > > map = new ConcurrentHashMap<>();
private final ClassCopier< T > copier;
private final Class< ? >[] signature;
/**
* Create a ClassCopyProvider to make copy a a given class.
*
* @param clazz Class to be copied.
* @param interfaceOfClazz Interface that's implemented by the clazz. A class copies can only be used
* through this interface.
* @param constructorSignature Constructor signature to be used
* when creating a new instance with {@link #newInstanceForKey}
*/
public ClassCopyProvider( final Class< ? extends T > clazz, final Class< T > interfaceOfClazz, final Class< ? >... constructorSignature )
{
this.copier = new ClassCopier<>( clazz, interfaceOfClazz );
this.signature = ( constructorSignature == null || constructorSignature.length == 0 ) ? assumeConstructorSignature( clazz ) : constructorSignature;
}
private static Class< ? >[] assumeConstructorSignature( final Class< ? > clazz )
{
if ( hasDefaultConstructor( clazz ) )
return new Class[ 0 ];
final Constructor< ? >[] constructors = clazz.getConstructors();
if ( constructors.length == 1 )
return constructors[ 0 ].getParameterTypes();
if ( constructors.length == 0 )
throw new IllegalArgumentException( "ClassCopyProvider: Class and it's constructor need to be public (" + clazz.getName() + ")." );
throw new IllegalArgumentException( "ClassCopyProvider: Please specify constructor signature." );
}
private static boolean hasDefaultConstructor( final Class< ? > clazz )
{
return Stream.of( clazz.getConstructors() )
.anyMatch( constructor -> constructor.getParameterCount() == 0 );
}
private Class< ? extends T > classForKey( final Object key )
{
return map.computeIfAbsent( key, k -> copier.copy() );
}
/**
* Returns true if the given list of objects,
* matches the constructor signature provided to {@link #ClassCopyProvider(Class, Class, Class[])}.
*/
public boolean matches( final Object... parameters )
{
if ( parameters.length != signature.length )
return false;
for ( int i = 0; i < signature.length; i++ )
if ( !signature[ i ].isInstance( parameters[ i ] ) )
return false;
return true;
}
/**
* Returns an instance of a copy of the original class, that has been provided to the constructor.
*
* Note: The returned object isn't an instance of the original class.
* {@link Class#isInstance(Object)} and "instanceof" will return false.
* And ClassCastException might occur if this is ignored.
*
* The returned instance has a copy of the byte code of the original class.
* This byte code is independently optimised by the JIT compiler.
* The JIT compiler will optimise the byte code, if it's only used in a specific use case.
* If used wisely a performance increase is the consequence.
*
* @param key Instances created with the same key, share their byte code.
* @param parameters Parameters that are passed to the constructor.
*/
public T newInstanceForKey( final Object key, final Object... parameters )
{
try
{
return classForKey( key ).getConstructor( signature ).newInstance( parameters );
}
catch ( final Exception e )
{
throw new RuntimeException( e );
}
}
}