Aapt2 ValueTransformer
For future macro support, aapt2 must be able to convert Reference
values into other Value types. Currently a DescendingValueVisitor is
used to visit all of the References in a ResourceTable or a compiled
XML file to set their resource ids during the link phase. This was fine
since we were only mutating the resource id of the visited Reference.
A macro may reference a String, BinaryPrimitive, or any other Item
type. During the link phase, we will need to transform references to
macros into the values of the macros.
The only parameter in the methods of the ValueVisitor interface is a
raw pointer to the type being visited. The visitor interface does not
support reassigning the visited type to a different type.
ValueTransformer is a new interface for consuming a Value type and
transforming it into a compatible Value type. This change refactors
Value::Clone to use this interface.
Bug: 175616308
Test: aapt2_tests
Change-Id: Ic1b9d718b932c208764114cd9c74d880e189ccb0
diff --git a/tools/aapt2/ValueTransformer_inline.h b/tools/aapt2/ValueTransformer_inline.h
new file mode 100644
index 0000000..c6c07c0
--- /dev/null
+++ b/tools/aapt2/ValueTransformer_inline.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#ifndef AAPT_VALUE_TRANSFORMER_IMPL_H
+#define AAPT_VALUE_TRANSFORMER_IMPL_H
+
+namespace aapt {
+
+inline ValueTransformer::ValueTransformer(StringPool* new_pool) : pool_(new_pool) {
+}
+
+template <typename Derived, typename Base>
+inline std::unique_ptr<Derived> TransformableValue<Derived, Base>::Transform(
+ ValueTransformer& transformer) const {
+ return transformer.TransformDerived(static_cast<const Derived*>(this));
+}
+
+template <typename Derived, typename Base>
+Value* TransformableValue<Derived, Base>::TransformValueImpl(ValueTransformer& transformer) const {
+ auto self = static_cast<const Derived*>(this);
+ auto transformed = transformer.TransformValue(self);
+ return transformed.release();
+}
+
+template <typename Derived, typename Base>
+Item* TransformableItem<Derived, Base>::TransformItemImpl(ValueTransformer& transformer) const {
+ auto self = static_cast<const Derived*>(this);
+ auto transformed = transformer.TransformItem(self);
+ return transformed.release();
+}
+
+} // namespace aapt
+
+#endif // AAPT_VALUE_TRANSFORMER_IMPL_H
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