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.ClassVisitor; 20import org.objectweb.asm.MethodVisitor; 21import org.objectweb.asm.Opcodes; 22 23import java.util.Set; 24 25/** 26 * A {@link DelegateClassAdapter} can transform some methods from a class into 27 * delegates that defer the call to an associated delegate class. 28 * <p/> 29 * This is used to override specific methods and or all native methods in classes. 30 */ 31public class DelegateClassAdapter extends ClassVisitor { 32 33 /** Suffix added to original methods. */ 34 private static final String ORIGINAL_SUFFIX = "_Original"; 35 private static final String CONSTRUCTOR = "<init>"; 36 private static final String CLASS_INIT = "<clinit>"; 37 38 public static final String ALL_NATIVES = "<<all_natives>>"; 39 40 private final String mClassName; 41 private final Set<String> mDelegateMethods; 42 private final Log mLog; 43 44 /** 45 * Creates a new {@link DelegateClassAdapter} that can transform some methods 46 * from a class into delegates that defer the call to an associated delegate class. 47 * <p/> 48 * This is used to override specific methods and or all native methods in classes. 49 * 50 * @param log The logger object. Must not be null. 51 * @param cv the class visitor to which this adapter must delegate calls. 52 * @param className The internal class name of the class to visit, 53 * e.g. <code>com/android/SomeClass$InnerClass</code>. 54 * @param delegateMethods The set of method names to modify and/or the 55 * special constant {@link #ALL_NATIVES} to convert all native methods. 56 */ 57 public DelegateClassAdapter(Log log, 58 ClassVisitor cv, 59 String className, 60 Set<String> delegateMethods) { 61 super(Opcodes.ASM4, cv); 62 mLog = log; 63 mClassName = className; 64 mDelegateMethods = delegateMethods; 65 } 66 67 //---------------------------------- 68 // Methods from the ClassAdapter 69 70 @Override 71 public MethodVisitor visitMethod(int access, String name, String desc, 72 String signature, String[] exceptions) { 73 74 boolean isStatic = (access & Opcodes.ACC_STATIC) != 0; 75 boolean isNative = (access & Opcodes.ACC_NATIVE) != 0; 76 77 boolean useDelegate = (isNative && mDelegateMethods.contains(ALL_NATIVES)) || 78 mDelegateMethods.contains(name); 79 80 if (!useDelegate) { 81 // Not creating a delegate for this method, pass it as-is from the reader to the writer. 82 return super.visitMethod(access, name, desc, signature, exceptions); 83 } 84 85 if (CONSTRUCTOR.equals(name) || CLASS_INIT.equals(name)) { 86 // We don't currently support generating delegates for constructors. 87 throw new UnsupportedOperationException( 88 String.format( 89 "Delegate doesn't support overriding constructor %1$s:%2$s(%3$s)", //$NON-NLS-1$ 90 mClassName, name, desc)); 91 } 92 93 if (isNative) { 94 // Remove native flag 95 access = access & ~Opcodes.ACC_NATIVE; 96 MethodVisitor mwDelegate = super.visitMethod(access, name, desc, signature, exceptions); 97 98 DelegateMethodAdapter a = new DelegateMethodAdapter( 99 mLog, null, mwDelegate, mClassName, name, desc, isStatic); 100 101 // A native has no code to visit, so we need to generate it directly. 102 a.generateDelegateCode(); 103 104 return mwDelegate; 105 } 106 107 // Given a non-native SomeClass.MethodName(), we want to generate 2 methods: 108 // - A copy of the original method named SomeClass.MethodName_Original(). 109 // The content is the original method as-is from the reader. 110 // - A brand new implementation of SomeClass.MethodName() which calls to a 111 // non-existing method named SomeClass_Delegate.MethodName(). 112 // The implementation of this 'delegate' method is done in layoutlib_bridge. 113 114 int accessDelegate = access; 115 access = access & ~Opcodes.ACC_PRIVATE; // If private, make it package protected. 116 117 MethodVisitor mwOriginal = super.visitMethod(access, name + ORIGINAL_SUFFIX, 118 desc, signature, exceptions); 119 MethodVisitor mwDelegate = super.visitMethod(accessDelegate, name, 120 desc, signature, exceptions); 121 122 return new DelegateMethodAdapter( 123 mLog, mwOriginal, mwDelegate, mClassName, name, desc, isStatic); 124 } 125} 126