com.github.stokito.gag.agent.AnswerToLifeGenerator.java Source code

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Here is the source code for com.github.stokito.gag.agent.AnswerToLifeGenerator.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.github.stokito.gag.agent;

import com.google.common.collect.ImmutableList;
import com.github.stokito.gag.annotation.enforceable.AnswerToTheUltimateQuestionOfLifeTheUniverseAndEverything;
import com.github.stokito.gag.instrument.AnnotationStateError;
import com.github.stokito.gag.instrument.ClassGenerator;
import com.github.stokito.gag.instrument.info.AnnoInfo;
import com.github.stokito.gag.instrument.info.ClassInfo;
import com.github.stokito.gag.instrument.info.LocalVarInfo;
import com.github.stokito.gag.instrument.info.MethodInfo;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;

import java.util.List;

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

public class AnswerToLifeGenerator extends ClassGenerator {

    private static final Type ANSWER_TYPE = Type
            .getType(AnswerToTheUltimateQuestionOfLifeTheUniverseAndEverything.class);

    private static final int FORTY_TWO = 42;

    @Override
    protected boolean canInstrument(ClassInfo classInfo) {
        return classInfo.hasLocalVarAnnoAnywhere(ANSWER_TYPE);
    }

    /** Supported types that have a valueOf(String) method. */
    private final List<Type> supportedValueOfTypes = ImmutableList.of(Type.getType(Integer.class),
            Type.getType(Long.class), Type.getType(Double.class), Type.getType(Float.class),
            Type.getType(Byte.class), Type.getType(Short.class));

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

        MethodVisitor mv = writer().visitMethod(access, name, desc, sig, exceptions);
        mv.visitCode();

        MethodInfo method = classInfo().getMethod(name, desc);
        for (LocalVarInfo param : method.getLocalVars()) {
            AnnoInfo anno = param.getAnnoFor(ANSWER_TYPE);
            if (anno == null) {
                continue;
            }

            Type paramType = param.getType();
            switch (paramType.getSort()) {
            case Type.INT:
            case Type.BYTE:
            case Type.CHAR:
            case Type.SHORT:
                mv.visitLdcInsn(FORTY_TWO);
                mv.visitVarInsn(ISTORE, param.getIndex());
                break;
            case Type.LONG:
                mv.visitLdcInsn((long) FORTY_TWO);
                mv.visitVarInsn(LSTORE, param.getIndex());
                break;
            case Type.DOUBLE:
                mv.visitLdcInsn((double) FORTY_TWO);
                mv.visitVarInsn(DSTORE, param.getIndex());
                break;
            case Type.FLOAT:
                mv.visitLdcInsn((float) FORTY_TWO);
                mv.visitVarInsn(FSTORE, param.getIndex());
                break;
            case Type.OBJECT:
                visitObject(mv, param);
                break;
            default:
                throwUnsupportedException(param);
            }

            setInstrumented(true);
        }

        mv.visitEnd();
        return mv;
    }

    /** TODO: Support BigDecimal and BigInteger. */
    private void visitObject(MethodVisitor mv, LocalVarInfo param) {
        Type paramType = param.getType();
        if (Type.getType(Character.class).equals(paramType)) {
            mv.visitLdcInsn((char) FORTY_TWO);
            mv.visitMethodInsn(INVOKESTATIC, paramType.getInternalName(), "valueOf",
                    "(C)L" + paramType.getInternalName() + ";");
            mv.visitVarInsn(ASTORE, param.getIndex());
        } else if (supportedValueOfTypes.contains(paramType)) {
            mv.visitLdcInsn(String.valueOf(FORTY_TWO));
            mv.visitMethodInsn(INVOKESTATIC, paramType.getInternalName(), "valueOf",
                    "(Ljava/lang/String;)L" + paramType.getInternalName() + ";");
            mv.visitVarInsn(ASTORE, param.getIndex());
        } else {
            throwUnsupportedException(param);
        }
    }

    private void throwUnsupportedException(LocalVarInfo param) {
        throw new AnnotationStateError("Unsupported parameter type (" + param.getType() + ") for "
                + AnswerToTheUltimateQuestionOfLifeTheUniverseAndEverything.class);

    }
}