io.syncframework.optimizer.OInitializerClassVisitor.java Source code

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Here is the source code for io.syncframework.optimizer.OInitializerClassVisitor.java

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/*
 * Copyright 2016 SyncObjects Ltda.
 * 
 * Licensed 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.
 */
package io.syncframework.optimizer;

import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;

import io.syncframework.api.ApplicationContext;

/**
 * @author dfroz
 */
public class OInitializerClassVisitor extends ClassVisitor {
    private OInitializerReflector reflector;

    public OInitializerClassVisitor(ClassVisitor cv, OInitializerReflector reflector) {
        super(Opcodes.ASM5, cv);
        this.reflector = reflector;
    }

    /**
     * This method will include the IController interface to the class definition.
     */
    @Override
    public void visit(int version, int access, String name, String signature, String superName,
            String[] interfaces) {
        String ninterfaces[] = new String[interfaces.length + 1];
        System.arraycopy(interfaces, 0, ninterfaces, 0, interfaces.length);
        ninterfaces[ninterfaces.length - 1] = Type.getInternalName(OInitializer.class);
        cv.visit(version, access, name, signature, superName, ninterfaces);
    }

    /**
     * Add code to the end of the class. We are adding the IController methods
     * @see org.objectweb.asm.ClassVisitor#visitEnd()
     */
    @Override
    public void visitEnd() {
        createContextMethod("_asApplicationContext", Type.getDescriptor(ApplicationContext.class),
                reflector.getApplicationContext());
        createInitMethod();
        createDestroyMethod();
    }

    /**
     * Generates the code:
     * 
     * public void _asDestroy() {
     *    return destroy();
     * }
     */
    public void createDestroyMethod() {
        MethodVisitor mv = cv.visitMethod(Opcodes.ACC_PUBLIC, "_asDestroy", "()V", null, null);
        Label l0 = new Label();
        if (reflector.getInit() != null) {
            mv.visitLabel(l0);
            mv.visitVarInsn(Opcodes.ALOAD, 0);
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, reflector.getClazzInternalName(), "destroy", "()V", false);
            mv.visitInsn(Opcodes.RETURN);
        } else {
            mv.visitLabel(l0);
            mv.visitInsn(Opcodes.RETURN);
        }

        Label l1 = new Label();
        mv.visitLocalVariable("this", reflector.getClazzDescriptor(), null, l0, l1, 0);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
    }

    /**
     * Generates the code:
     * 
     * public void _asInit() {
     *    return init();
     * }
     */
    public void createInitMethod() {
        MethodVisitor mv = cv.visitMethod(Opcodes.ACC_PUBLIC, "_asInit", "()V", null, null);
        Label l0 = new Label();
        if (reflector.getInit() != null) {
            mv.visitLabel(l0);
            mv.visitVarInsn(Opcodes.ALOAD, 0);
            mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, reflector.getClazzInternalName(), "init", "()V", false);
            mv.visitInsn(Opcodes.RETURN);
        } else {
            mv.visitLabel(l0);
            mv.visitInsn(Opcodes.RETURN);
        }
        Label l1 = new Label();
        mv.visitLocalVariable("this", reflector.getClazzDescriptor(), null, l0, l1, 0);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
    }

    /**
     * Generates Contexts setter method: 
     * 
     * public void _as(Application|Error|Message|...)Context((Application|Error|Message|...)Context variable) {
     *    this.variable = variable
     *       or
     *    // do nothing
     * }
     */
    private void createContextMethod(String methodName, String typeDescriptor, String variableName) {
        if (variableName != null) {
            MethodVisitor mv = cv.visitMethod(Opcodes.ACC_PUBLIC, methodName, "(" + typeDescriptor + ")V", null,
                    null);
            Label l0 = new Label();
            Label l1 = new Label();
            Label l2 = new Label();
            mv.visitLabel(l0);
            mv.visitVarInsn(Opcodes.ALOAD, 0);
            mv.visitVarInsn(Opcodes.ALOAD, 1);
            mv.visitFieldInsn(Opcodes.PUTFIELD, reflector.getClazzInternalName(), variableName, typeDescriptor);
            mv.visitLabel(l1);
            mv.visitInsn(Opcodes.RETURN);
            mv.visitLabel(l2);
            mv.visitLocalVariable("this", reflector.getClazzDescriptor(), null, l0, l2, 0);
            mv.visitLocalVariable(variableName, typeDescriptor, null, l0, l2, 1);
            mv.visitMaxs(2, 2);
            mv.visitEnd();
        } else {
            MethodVisitor mv = cv.visitMethod(Opcodes.ACC_PUBLIC, methodName, "(" + typeDescriptor + ")V", null,
                    null);
            Label l0 = new Label();
            Label l1 = new Label();
            mv.visitLabel(l0);
            mv.visitInsn(Opcodes.RETURN);
            mv.visitLabel(l1);
            mv.visitLocalVariable("this", reflector.getClazzDescriptor(), null, l0, l1, 0);
            mv.visitLocalVariable("argument", typeDescriptor, null, l0, l1, 1);
        }
    }
}