DelegateClassAdapter.java revision bc101806249eb883f89c4a770a8c27f9ac315837 
1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.tools.layoutlib.create;
18
19import org.objectweb.asm.ClassAdapter;
20import org.objectweb.asm.ClassVisitor;
21import org.objectweb.asm.MethodVisitor;
22import org.objectweb.asm.Opcodes;
23
24import java.util.Set;
25
26/**
27 * A {@link DelegateClassAdapter} can transform some methods from a class into
28 * delegates that defer the call to an associated delegate class.
29 * <p/>
30 * This is used to override specific methods and or all native methods in classes.
31 */
32public class DelegateClassAdapter extends ClassAdapter {
33
34    public final static String ALL_NATIVES = "<<all_natives>>";
35
36    private final String mClassName;
37    private final Set<String> mDelegateMethods;
38    private final Log mLog;
39
40    /**
41     * Creates a new {@link DelegateClassAdapter} that can transform some methods
42     * from a class into delegates that defer the call to an associated delegate class.
43     * <p/>
44     * This is used to override specific methods and or all native methods in classes.
45     *
46     * @param log The logger object. Must not be null.
47     * @param cv the class visitor to which this adapter must delegate calls.
48     * @param className The internal class name of the class to visit,
49     *          e.g. <code>com/android/SomeClass$InnerClass</code>.
50     * @param delegateMethods The set of method names to modify and/or the
51     *          special constant {@link #ALL_NATIVES} to convert all native methods.
52     */
53    public DelegateClassAdapter(Log log,
54            ClassVisitor cv,
55            String className,
56            Set<String> delegateMethods) {
57        super(cv);
58        mLog = log;
59        mClassName = className;
60        mDelegateMethods = delegateMethods;
61    }
62
63    //----------------------------------
64    // Methods from the ClassAdapter
65
66    @Override
67    public MethodVisitor visitMethod(int access, String name, String desc,
68            String signature, String[] exceptions) {
69
70        boolean isStatic = (access & Opcodes.ACC_STATIC) != 0;
71        boolean isNative = (access & Opcodes.ACC_NATIVE) != 0;
72
73        boolean useDelegate = (isNative && mDelegateMethods.contains(ALL_NATIVES)) ||
74                              mDelegateMethods.contains(name);
75
76        if (useDelegate) {
77            // remove native
78            access = access & ~Opcodes.ACC_NATIVE;
79        }
80
81        MethodVisitor mw = super.visitMethod(access, name, desc, signature, exceptions);
82        if (useDelegate) {
83            DelegateMethodAdapter a = new DelegateMethodAdapter(mLog, mw, mClassName,
84                                                                name, desc, isStatic);
85            if (isNative) {
86                // A native has no code to visit, so we need to generate it directly.
87                a.generateCode();
88            } else {
89                return a;
90            }
91        }
92        return mw;
93    }
94}
95