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// Copyright 2018 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.android.desugar;
import com.google.devtools.build.android.desugar.io.BitFlags;
import java.util.Collections;
import java.util.LinkedHashSet;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Opcodes;
/**
* Visitor that renames emulated interfaces and marks classes that extend emulated interfaces to
* also implement the renamed interfaces. {@link DefaultMethodClassFixer} makes sure the requisite
* methods are present in all classes implementing the renamed interface. Doing this helps with
* dynamic dispatch on emulated interfaces.
*/
public class EmulatedInterfaceRewriter extends ClassVisitor {
private static final String[] EMPTY_ARRAY = new String[0];
private final CoreLibrarySupport support;
public EmulatedInterfaceRewriter(ClassVisitor dest, CoreLibrarySupport support) {
super(Opcodes.ASM6, dest);
this.support = support;
}
@Override
public void visit(
int version,
int access,
String name,
String signature,
String superName,
String[] interfaces) {
boolean emulated = support.isEmulatedCoreClassOrInterface(name);
{
// 1. see if we should implement any additional interfaces.
// Use LinkedHashSet to dedupe but maintain deterministic order
LinkedHashSet<String> newInterfaces = new LinkedHashSet<>();
if (interfaces != null && interfaces.length > 0) {
// Make classes implementing emulated interfaces also implement the renamed interfaces we
// create below. This includes making the renamed interfaces extends each other as needed.
Collections.addAll(newInterfaces, interfaces);
for (String itf : interfaces) {
if (support.isEmulatedCoreClassOrInterface(itf)) {
newInterfaces.add(support.renameCoreLibrary(itf));
}
}
}
if (!emulated) {
// For an immediate subclass of an emulated class, also fill in any interfaces implemented
// by superclasses, similar to the additional default method stubbing performed in
// DefaultMethodClassFixer in this situation.
Class<?> superclass = support.getEmulatedCoreClassOrInterface(superName);
while (superclass != null) {
for (Class<?> implemented : superclass.getInterfaces()) {
String itf = implemented.getName().replace('.', '/');
if (support.isEmulatedCoreClassOrInterface(itf)) {
newInterfaces.add(support.renameCoreLibrary(itf));
}
}
superclass = superclass.getSuperclass();
}
}
// Update implemented interfaces and signature if we did anything above
if (interfaces == null
? !newInterfaces.isEmpty()
: interfaces.length != newInterfaces.size()) {
interfaces = newInterfaces.toArray(EMPTY_ARRAY);
signature = null; // additional interfaces invalidate any signature
}
}
// 2. see if we need to rename this interface itself
if (BitFlags.isInterface(access) && emulated) {
name = support.renameCoreLibrary(name);
}
super.visit(version, access, name, signature, superName, interfaces);
}
}
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