net.imglib2.loops.ClassCopier Maven / Gradle / Ivy
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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.
* %%
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* modification, are permitted provided that the following conditions are met:
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package net.imglib2.loops;
import java.io.DataInputStream;
import java.io.IOException;
/**
* {@link ClassCopier} helps copying a class. The resulting class works as the
* original.
*
* Why would you want to copy a class?
*
* The problem is described in https://github.com/tpietzsch/none/.
* The solution suggested there is to copy a specific method of a class, but
* copying a whole class is easier.
*
* @author Matthias Arzt
*/
class ClassCopier< T >
{
private final Class< ? extends T > original;
private final byte[] bytes;
public ClassCopier( final Class< ? extends T > original, final Class< T > interfaceOfOriginal )
{
if ( !interfaceOfOriginal.isAssignableFrom( original ) || interfaceOfOriginal.equals( original ) )
throw new IllegalArgumentException( "\"original\" must be a implementation of interface \"interfaceOfOriginal\"" );
this.original = original;
this.bytes = classToBytes( original );
}
public Class< ? extends T > copy()
{
@SuppressWarnings( "unchecked" )
final Class< ? extends T > copy = ( Class< ? extends T > ) new ClassCopyLoader( original.getClassLoader() ).bytesToClass( original.getName(), bytes );
return copy;
}
private byte[] classToBytes( final Class< ? > aClass )
{
final String className = aClass.getName();
final String classAsPath = className.replace( '.', '/' ) + ".class";
try (DataInputStream stream = new DataInputStream( aClass.getClassLoader().getResourceAsStream( classAsPath ) ))
{
final byte[] bytes = new byte[ stream.available() ];
stream.readFully( bytes );
return bytes;
}
catch ( final IOException e )
{
throw new RuntimeException( e );
}
}
private static class ClassCopyLoader extends ClassLoader
{
public ClassCopyLoader( ClassLoader parent )
{
super( parent );
}
private Class< ? > bytesToClass( final String className, final byte[] bytes )
{
final Class< ? > copiedClass = super.defineClass( className, bytes, 0, bytes.length );
super.resolveClass( copiedClass );
return copiedClass;
}
}
}