plugins/org.eclipse.objectteams.otredyn/src/org/eclipse/objectteams/otredyn/bytecode/asm/CreateFieldAccessAdapter.java

/**********************************************************************
 * This file is part of "Object Teams Dynamic Runtime Environment"
 * 
 * Copyright 2009, 2012 Oliver Frank and others.
 * 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Please visit http://www.eclipse.org/objectteams for updates and contact.
 * 
 * Contributors:
 *		Oliver Frank - Initial API and implementation
 *		Stephan Herrmann - Initial API and implementation
 **********************************************************************/
package org.eclipse.objectteams.otredyn.bytecode.asm;

import org.eclipse.objectteams.otredyn.bytecode.Field;
import org.eclipse.objectteams.otredyn.bytecode.Method;
import org.eclipse.objectteams.otredyn.transformer.names.ConstantMembers;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.FieldInsnNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.InsnNode;
import org.objectweb.asm.tree.IntInsnNode;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.TypeInsnNode;

/**
 * Creates and adds the instructions,
 * that are needed to access a not visible field from the team
 * in the method access or accessStatic as follows:<br/> <br/>
 * case (memberId) { // generated by CreateSwitchForAccessAdapter <br/>
 *     if (opKind == 0) { <br/>
 *         return field; <br/>
 *     } else { <br/>
 *         field = args[0]; <br/>
 *     } <br/>
 *     break; <br/>
 * }
 * 
 * @author Oliver Frank
 */
public class CreateFieldAccessAdapter extends AbstractTransformableClassNode {

	private Field field;
	private int accessId;
	private Method access;
	private int firstArgIndex;

	public CreateFieldAccessAdapter(Field field, int accessId) {
		this.field = field;
		this.accessId = accessId;
		if (field.isStatic()) {
			access = ConstantMembers.accessStatic;
			firstArgIndex = 0;
		} else {
			access = ConstantMembers.access;
			firstArgIndex = 1;
		}
	}

	@Override
	public void transform() {

		InsnList instructions = new InsnList();
		// put accessId on the stack
		instructions.add(new IntInsnNode(Opcodes.ILOAD, firstArgIndex + 1));
		// read or write access
		LabelNode writeAccess = new LabelNode();
		instructions.add(new JumpInsnNode(Opcodes.IFNE, writeAccess));
		// read access
		if (field.isStatic()) {
			// get value of field
			instructions.add(new FieldInsnNode(Opcodes.GETSTATIC, name, field
					.getName(), field.getSignature()));
		} else {
			// put "this" on the stack
			instructions.add(new IntInsnNode(Opcodes.ALOAD, 0));
			// get value of field
			instructions.add(new FieldInsnNode(Opcodes.GETFIELD, name, field
					.getName(), field.getSignature()));
		}

		//box value as "Object"
		Type type = Type.getType(field.getSignature());
		instructions.add(AsmTypeHelper.getBoxingInstructionForType(type));
		instructions.add(new InsnNode(Opcodes.ARETURN));
		
		//write access
		instructions.add(writeAccess);
		//put "args" on the stack 
		instructions.add(new IntInsnNode(Opcodes.ALOAD, firstArgIndex + 2));
		//get the first element of "args"
		instructions.add(new InsnNode(Opcodes.ICONST_0));
		instructions.add(new InsnNode(Opcodes.AALOAD));
		//unbox it
		if (type.getSort() != Type.ARRAY && type.getSort() != Type.OBJECT) {
			String objectType = AsmTypeHelper.getObjectType(type);
			instructions.add(new TypeInsnNode(Opcodes.CHECKCAST, objectType));
			instructions.add(AsmTypeHelper.getUnboxingInstructionForType(type, objectType));
		} else {
			instructions.add(new TypeInsnNode(Opcodes.CHECKCAST, type.getInternalName()));
		}
		
		if (field.isStatic()) {
			//save value in field
			instructions.add(new FieldInsnNode(Opcodes.PUTSTATIC, name, field.getName(), field.getSignature()));
		} else {
			//put "this" on the stack
			instructions.add(new IntInsnNode(Opcodes.ALOAD, 0));
			instructions.add(new InsnNode(Opcodes.SWAP));
			//save value in field
			instructions.add(new FieldInsnNode(Opcodes.PUTFIELD, name, field.getName(), field.getSignature()));
		}
		
		//dummy return 
		instructions.add(new InsnNode(Opcodes.ACONST_NULL));
		instructions.add(new InsnNode(Opcodes.ARETURN));
		
		//add the instructions to a new label in the existing switch
		MethodNode method = getMethod(access);
		addNewLabelToSwitch(method.instructions, instructions, accessId);
	}

}