1 files changed, 92 insertions, 0 deletions
diff --git a/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java b/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java
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+++ b/java/com/google/devtools/build/android/desugar/EmulatedInterfaceRewriter.java
@@ -0,0 +1,92 @@
+// 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);
+  }
+}