com.android.ide.eclipse.apt.internal.analysis.StaticVirtualAnalyzer.java Source code

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Here is the source code for com.android.ide.eclipse.apt.internal.analysis.StaticVirtualAnalyzer.java

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/**
 * Copyright (C) Mattia Gustarini
 * 
 * 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.android.ide.eclipse.apt.internal.analysis;

import java.util.Collection;
import java.util.LinkedList;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;

/**
 * This analyzer checks if there are virtual methods that can be made static
 * following the guideline:<br/>
 * @see <a href="http://developer.android.com/guide/practices/design/performance.html#prefer_static">Prefer Static Over Virtual</a>
 * @author Mattia Gustarini
 * This analyzer can give false positive in case of Override methods that doesn't access the object instance in its body
 */
public final class StaticVirtualAnalyzer extends SpecificAnalyzer {
    protected final class StaticVirtualProblem extends Problem {

        public StaticVirtualProblem(final AbstractInsnNode insnNode) {
            super(insnNode);
            mLine -= 1;
        }
    }

    public StaticVirtualAnalyzer() {
        super("Prefer Static Over Virtual", "If a method doesn't access object fields make it static!");
    }

    /* (non-Javadoc)
     * @see com.android.ide.eclipse.apt.internal.analysis.SpecificAnalyzer#analyzeClass(org.objectweb.asm.tree.ClassNode)
     */
    @Override
    protected Collection<Problem> analyzeClass(final ClassNode classNode) {
        final Collection<Problem> problems = new LinkedList<Problem>();
        if ((classNode.access & Opcodes.ACC_INTERFACE) == 0) {
            problems.addAll(super.analyzeClass(classNode));
        }
        return problems;
    }

    /* (non-Javadoc)
     * @see ch.usi.inf.gustarim.apt.analysis.SpecificAnalyzer#analyzeMethod(org.objectweb.asm.tree.MethodNode)
     */
    @Override
    protected Collection<Problem> analyzeMethod(final MethodNode methodNode) {
        final Collection<Problem> problems = new LinkedList<Problem>();
        final int acc = methodNode.access;
        if ((acc & Opcodes.ACC_STATIC) == 0 && (acc & Opcodes.ACC_ABSTRACT) == 0) {
            final InsnList instructions = methodNode.instructions;
            //find if a method load this (ALOAD 0)
            boolean aload0 = false;
            for (int i = 0; i < instructions.size(); i++) {
                final AbstractInsnNode instruction = instructions.get(i);
                if (instruction.getOpcode() == Opcodes.ALOAD) {
                    final VarInsnNode aload = (VarInsnNode) instruction;
                    aload0 = aload.var == 0;
                    if (aload0) {
                        break;
                    }
                }
            }
            if (!aload0) {
                final Problem problem = new StaticVirtualProblem(instructions.get(1));
                problems.add(problem);
            }
        }
        return problems;
    }
}