suneido.runtime.DynamicIndy.java Source code

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Here is the source code for suneido.runtime.DynamicIndy.java

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/* Copyright 2012 (c) Suneido Software Corp. All rights reserved.
 * Licensed under GPLv2.
 */

package suneido.runtime;

import static org.objectweb.asm.Opcodes.*;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;

/**
 * Modified from the code published by Remi Forax, as attachment to this blog
 * post:
 * <http://weblogs.java.net/blog/forax/archive/2011/01/07/call-invokedynamic
 * -java>
 *
 * @author Attila Szegedi
 */
public class DynamicIndy extends ClassLoader {
    private int ID_GENERATOR = 0;

    public MethodHandle invokeDynamic(String name, MethodType desc, Class<?> bsmClass, String bsmName,
            MethodType bsmType, Object... bsmArgs) {
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
        cw.visit(V1_7, ACC_PUBLIC | ACC_SUPER, "Gen" + (ID_GENERATOR++), null, "java/lang/Object", null);

        MethodVisitor init = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        init.visitCode();
        init.visitVarInsn(ALOAD, 0);
        init.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
        init.visitInsn(RETURN);
        init.visitMaxs(-1, -1);
        init.visitEnd();

        String descriptor = desc.toMethodDescriptorString();

        MethodVisitor mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "invokedynamic", descriptor, null, null);
        int slot = 0;
        for (Type parameterType : Type.getArgumentTypes(descriptor)) {
            mv.visitVarInsn(parameterType.getOpcode(ILOAD), slot);
            slot += parameterType.getSize();
        }

        mv.visitInvokeDynamicInsn(name, descriptor, new org.objectweb.asm.Handle(H_INVOKESTATIC,
                bsmClass.getName().replace('.', '/'), bsmName, bsmType.toMethodDescriptorString(), false), bsmArgs);

        Type returnType = Type.getReturnType(descriptor);
        mv.visitInsn(returnType.getOpcode(IRETURN));

        mv.visitMaxs(-1, -1);
        mv.visitEnd();

        cw.visitEnd();

        byte[] array = cw.toByteArray();
        Class<?> clazz = defineClass(null, array, 0, array.length);

        try {
            return MethodHandles.lookup().findStatic(clazz, "invokedynamic", desc);
        } catch (IllegalAccessException | NoSuchMethodException e) {
            throw (AssertionError) new AssertionError().initCause(e);
        }
    }
}