com.google.code.jconts.instrument.gen.TramplineMethodGenerator.java Source code

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Here is the source code for com.google.code.jconts.instrument.gen.TramplineMethodGenerator.java

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/**
 * Copyright (C) 2011 Ivan Dubrov
 *
 * 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 com.google.code.jconts.instrument.gen;

import static com.google.code.jconts.instrument.Constants.*;

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

import com.google.code.jconts.instrument.context.MethodContext;

/**
 * This class replaces original asynchronous method with one that will create
 * instance of <code>com.google.code.jconts.Computation</code> and return it.
 */
public class TramplineMethodGenerator {

    private final MethodContext info;

    public TramplineMethodGenerator(MethodContext info) {
        this.info = info;
    }

    public void accept(ClassVisitor cv) {
        MethodVisitor mv = cv.visitMethod(info.access, info.name, info.desc, info.signature, info.exceptions);
        mv.visitCode();
        mv.visitTypeInsn(Opcodes.NEW, info.computationClassName);
        mv.visitInsn(Opcodes.DUP);

        // "this' for new Computation(this, state)
        if (!info.isStatic()) {
            mv.visitVarInsn(Opcodes.ALOAD, 0);
        }

        // new State()
        mv.visitTypeInsn(Opcodes.NEW, info.stateClassName);
        mv.visitInsn(Opcodes.DUP);
        mv.visitMethodInsn(Opcodes.INVOKESPECIAL, info.stateClassName, CTOR_NAME, DEFAULT_CTOR_DESC);

        // state.varX = argX
        String[] names = info.entryLocalsVars;
        for (int i = 0; i < info.entryLocals.length; ++i) {
            mv.visitInsn(Opcodes.DUP);
            mv.visitVarInsn(info.entryLocals[i].getOpcode(Opcodes.ILOAD), i + info.thisOffset);
            mv.visitFieldInsn(Opcodes.PUTFIELD, info.stateClassName, names[i], info.entryLocals[i].getDescriptor());
        }

        // new Computation(this, state);
        String ctorDesc;
        if (info.isStatic()) {
            ctorDesc = Type.getMethodDescriptor(Type.VOID_TYPE, new Type[] { info.stateType });
        } else {
            ctorDesc = Type.getMethodDescriptor(Type.VOID_TYPE,
                    new Type[] { Type.getObjectType(info.owner), info.stateType });
        }
        mv.visitMethodInsn(Opcodes.INVOKESPECIAL, info.computationClassName, CTOR_NAME, ctorDesc);

        mv.visitInsn(Opcodes.ARETURN);
        mv.visitMaxs(info.isStatic() ? 5 : 6,
                info.isStatic() ? info.entryLocals.length : info.entryLocals.length + 1);
        mv.visitEnd();
    }
}