com.google.gag.agent.NoopGenerator.java Source code

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Here is the source code for com.google.gag.agent.NoopGenerator.java

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/**
 * Copyright 2010 Google Inc.
 *
 * 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.gag.agent;

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

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

import com.google.gag.annotation.enforceable.Noop;
import com.google.gag.instrument.ClassGenerator;
import com.google.gag.instrument.info.ClassInfo;
import com.google.gag.instrument.info.MethodInfo;

public class NoopGenerator extends ClassGenerator {

    private static final Type NOOP_TYPE = Type.getType(Noop.class);

    @Override
    protected boolean canInstrument(ClassInfo classInfo) {
        return classInfo.hasAnno(NOOP_TYPE) || classInfo.hasMethodAnnoAnywhere(NOOP_TYPE);
    }

    @Override
    public MethodVisitor visitMethod(int access, String name, String desc, String sig, String[] exceptions) {

        boolean isNoopForAll = classInfo().getAnnoFor(NOOP_TYPE) != null;
        MethodVisitor mv = writer().visitMethod(access, name, desc, sig, exceptions);
        mv.visitCode();

        MethodInfo method = classInfo().getMethod(name, desc);
        boolean isConstructor = "<init>".equals(method.getName());
        boolean isNoopForMethod = method.getAnnoFor(NOOP_TYPE) != null;

        if (!isConstructor && (isNoopForAll || isNoopForMethod)) {
            Type returnType = Type.getReturnType(desc);
            switch (returnType.getSort()) {
            case Type.VOID:
                mv.visitInsn(RETURN);
                break;
            case Type.OBJECT:
            case Type.ARRAY:
                mv.visitInsn(Opcodes.ACONST_NULL);
                mv.visitInsn(ARETURN);
                break;
            case Type.DOUBLE:
                mv.visitInsn(DCONST_0);
                mv.visitInsn(DRETURN);
                break;
            case Type.FLOAT:
                mv.visitInsn(FCONST_0);
                mv.visitInsn(FRETURN);
                break;
            case Type.LONG:
                mv.visitInsn(LCONST_0);
                mv.visitInsn(LRETURN);
                break;
            case Type.INT:
            case Type.SHORT:
            case Type.CHAR:
            case Type.BYTE:
            case Type.BOOLEAN:
                mv.visitInsn(ICONST_0);
                mv.visitInsn(IRETURN);
                break;
            }
            setInstrumented(true);
        }

        mv.visitEnd();
        return mv;
    }
}