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/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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.tools.layoutlib.create;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import java.util.Set;
/**
* A {@link DelegateClassAdapter} can transform some methods from a class into
* delegates that defer the call to an associated delegate class.
* <p/>
* This is used to override specific methods and or all native methods in classes.
*/
public class DelegateClassAdapter extends ClassVisitor {
/** Suffix added to original methods. */
private static final String ORIGINAL_SUFFIX = "_Original";
private static final String CONSTRUCTOR = "<init>";
private static final String CLASS_INIT = "<clinit>";
public static final String ALL_NATIVES = "<<all_natives>>";
private final String mClassName;
private final Set<String> mDelegateMethods;
private final Log mLog;
private boolean mIsStaticInnerClass;
/**
* Creates a new {@link DelegateClassAdapter} that can transform some methods
* from a class into delegates that defer the call to an associated delegate class.
* <p/>
* This is used to override specific methods and or all native methods in classes.
*
* @param log The logger object. Must not be null.
* @param cv the class visitor to which this adapter must delegate calls.
* @param className The internal class name of the class to visit,
* e.g. <code>com/android/SomeClass$InnerClass</code>.
* @param delegateMethods The set of method names to modify and/or the
* special constant {@link #ALL_NATIVES} to convert all native methods.
*/
public DelegateClassAdapter(Log log,
ClassVisitor cv,
String className,
Set<String> delegateMethods) {
super(Opcodes.ASM4, cv);
mLog = log;
mClassName = className;
mDelegateMethods = delegateMethods;
// If this is an inner class, by default, we assume it's static. If it's not we will detect
// by looking at the fields (see visitField)
mIsStaticInnerClass = className.contains("$");
}
//----------------------------------
// Methods from the ClassAdapter
@Override
public FieldVisitor visitField(int access, String name, String desc, String signature,
Object value) {
if (mIsStaticInnerClass && "this$0".equals(name)) {
// Having a "this$0" field, proves that this class is not a static inner class.
mIsStaticInnerClass = false;
}
return super.visitField(access, name, desc, signature, value);
}
@Override
public MethodVisitor visitMethod(int access, String name, String desc,
String signature, String[] exceptions) {
boolean isStaticMethod = (access & Opcodes.ACC_STATIC) != 0;
boolean isNative = (access & Opcodes.ACC_NATIVE) != 0;
boolean useDelegate = (isNative && mDelegateMethods.contains(ALL_NATIVES)) ||
mDelegateMethods.contains(name);
if (!useDelegate) {
// Not creating a delegate for this method, pass it as-is from the reader to the writer.
return super.visitMethod(access, name, desc, signature, exceptions);
}
if (CONSTRUCTOR.equals(name) || CLASS_INIT.equals(name)) {
// We don't currently support generating delegates for constructors.
throw new UnsupportedOperationException(
String.format(
"Delegate doesn't support overriding constructor %1$s:%2$s(%3$s)", //$NON-NLS-1$
mClassName, name, desc));
}
if (isNative) {
// Remove native flag
access = access & ~Opcodes.ACC_NATIVE;
MethodVisitor mwDelegate = super.visitMethod(access, name, desc, signature, exceptions);
DelegateMethodAdapter a = new DelegateMethodAdapter(
mLog, null, mwDelegate, mClassName, name, desc, isStaticMethod,
mIsStaticInnerClass);
// A native has no code to visit, so we need to generate it directly.
a.generateDelegateCode();
return mwDelegate;
}
// Given a non-native SomeClass.MethodName(), we want to generate 2 methods:
// - A copy of the original method named SomeClass.MethodName_Original().
// The content is the original method as-is from the reader.
// - A brand new implementation of SomeClass.MethodName() which calls to a
// non-existing method named SomeClass_Delegate.MethodName().
// The implementation of this 'delegate' method is done in layoutlib_bridge.
int accessDelegate = access;
access = access & ~Opcodes.ACC_PRIVATE; // If private, make it package protected.
MethodVisitor mwOriginal = super.visitMethod(access, name + ORIGINAL_SUFFIX,
desc, signature, exceptions);
MethodVisitor mwDelegate = super.visitMethod(accessDelegate, name,
desc, signature, exceptions);
return new DelegateMethodAdapter(
mLog, mwOriginal, mwDelegate, mClassName, name, desc, isStaticMethod,
mIsStaticInnerClass);
}
}
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