AAPT2: Separate out the various steps
An early refactor. Some ideas became clearer as
development continued. Now the various phases are much
clearer and more easily reusable.
Also added a ton of tests!
Change-Id: Ic8f0a70c8222370352e63533b329c40457c0903e
diff --git a/tools/aapt2/util/Maybe.h b/tools/aapt2/util/Maybe.h
new file mode 100644
index 0000000..1f7d5ce
--- /dev/null
+++ b/tools/aapt2/util/Maybe.h
@@ -0,0 +1,280 @@
+/*
+ * Copyright (C) 2015 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_MAYBE_H
+#define AAPT_MAYBE_H
+
+#include <cassert>
+#include <type_traits>
+#include <utility>
+
+namespace aapt {
+
+/**
+ * Either holds a valid value of type T, or holds Nothing.
+ * The value is stored inline in this structure, so no
+ * heap memory is used when creating a Maybe<T> object.
+ */
+template <typename T>
+class Maybe {
+public:
+ /**
+ * Construct Nothing.
+ */
+ Maybe();
+
+ ~Maybe();
+
+ Maybe(const Maybe& rhs);
+
+ template <typename U>
+ Maybe(const Maybe<U>& rhs);
+
+ Maybe(Maybe&& rhs);
+
+ template <typename U>
+ Maybe(Maybe<U>&& rhs);
+
+ Maybe& operator=(const Maybe& rhs);
+
+ template <typename U>
+ Maybe& operator=(const Maybe<U>& rhs);
+
+ Maybe& operator=(Maybe&& rhs);
+
+ template <typename U>
+ Maybe& operator=(Maybe<U>&& rhs);
+
+ /**
+ * Construct a Maybe holding a value.
+ */
+ Maybe(const T& value);
+
+ /**
+ * Construct a Maybe holding a value.
+ */
+ Maybe(T&& value);
+
+ /**
+ * True if this holds a value, false if
+ * it holds Nothing.
+ */
+ explicit operator bool() const;
+
+ /**
+ * Gets the value if one exists, or else
+ * panics.
+ */
+ T& value();
+
+ /**
+ * Gets the value if one exists, or else
+ * panics.
+ */
+ const T& value() const;
+
+private:
+ template <typename U>
+ friend class Maybe;
+
+ template <typename U>
+ Maybe& copy(const Maybe<U>& rhs);
+
+ template <typename U>
+ Maybe& move(Maybe<U>&& rhs);
+
+ void destroy();
+
+ bool mNothing;
+
+ typename std::aligned_storage<sizeof(T), alignof(T)>::type mStorage;
+};
+
+template <typename T>
+Maybe<T>::Maybe()
+: mNothing(true) {
+}
+
+template <typename T>
+Maybe<T>::~Maybe() {
+ if (!mNothing) {
+ destroy();
+ }
+}
+
+template <typename T>
+Maybe<T>::Maybe(const Maybe& rhs)
+: mNothing(rhs.mNothing) {
+ if (!rhs.mNothing) {
+ new (&mStorage) T(reinterpret_cast<const T&>(rhs.mStorage));
+ }
+}
+
+template <typename T>
+template <typename U>
+Maybe<T>::Maybe(const Maybe<U>& rhs)
+: mNothing(rhs.mNothing) {
+ if (!rhs.mNothing) {
+ new (&mStorage) T(reinterpret_cast<const U&>(rhs.mStorage));
+ }
+}
+
+template <typename T>
+Maybe<T>::Maybe(Maybe&& rhs)
+: mNothing(rhs.mNothing) {
+ if (!rhs.mNothing) {
+ rhs.mNothing = true;
+
+ // Move the value from rhs.
+ new (&mStorage) T(std::move(reinterpret_cast<T&>(rhs.mStorage)));
+ rhs.destroy();
+ }
+}
+
+template <typename T>
+template <typename U>
+Maybe<T>::Maybe(Maybe<U>&& rhs)
+: mNothing(rhs.mNothing) {
+ if (!rhs.mNothing) {
+ rhs.mNothing = true;
+
+ // Move the value from rhs.
+ new (&mStorage) T(std::move(reinterpret_cast<U&>(rhs.mStorage)));
+ rhs.destroy();
+ }
+}
+
+template <typename T>
+inline Maybe<T>& Maybe<T>::operator=(const Maybe& rhs) {
+ // Delegate to the actual assignment.
+ return copy(rhs);
+}
+
+template <typename T>
+template <typename U>
+inline Maybe<T>& Maybe<T>::operator=(const Maybe<U>& rhs) {
+ return copy(rhs);
+}
+
+template <typename T>
+template <typename U>
+Maybe<T>& Maybe<T>::copy(const Maybe<U>& rhs) {
+ if (mNothing && rhs.mNothing) {
+ // Both are nothing, nothing to do.
+ return *this;
+ } else if (!mNothing && !rhs.mNothing) {
+ // We both are something, so assign rhs to us.
+ reinterpret_cast<T&>(mStorage) = reinterpret_cast<const U&>(rhs.mStorage);
+ } else if (mNothing) {
+ // We are nothing but rhs is something.
+ mNothing = rhs.mNothing;
+
+ // Copy the value from rhs.
+ new (&mStorage) T(reinterpret_cast<const U&>(rhs.mStorage));
+ } else {
+ // We are something but rhs is nothing, so destroy our value.
+ mNothing = rhs.mNothing;
+ destroy();
+ }
+ return *this;
+}
+
+template <typename T>
+inline Maybe<T>& Maybe<T>::operator=(Maybe&& rhs) {
+ // Delegate to the actual assignment.
+ return move(std::forward<Maybe<T>>(rhs));
+}
+
+template <typename T>
+template <typename U>
+inline Maybe<T>& Maybe<T>::operator=(Maybe<U>&& rhs) {
+ return move(std::forward<Maybe<U>>(rhs));
+}
+
+template <typename T>
+template <typename U>
+Maybe<T>& Maybe<T>::move(Maybe<U>&& rhs) {
+ if (mNothing && rhs.mNothing) {
+ // Both are nothing, nothing to do.
+ return *this;
+ } else if (!mNothing && !rhs.mNothing) {
+ // We both are something, so move assign rhs to us.
+ rhs.mNothing = true;
+ reinterpret_cast<T&>(mStorage) = std::move(reinterpret_cast<U&>(rhs.mStorage));
+ rhs.destroy();
+ } else if (mNothing) {
+ // We are nothing but rhs is something.
+ mNothing = false;
+ rhs.mNothing = true;
+
+ // Move the value from rhs.
+ new (&mStorage) T(std::move(reinterpret_cast<U&>(rhs.mStorage)));
+ rhs.destroy();
+ } else {
+ // We are something but rhs is nothing, so destroy our value.
+ mNothing = true;
+ destroy();
+ }
+ return *this;
+}
+
+template <typename T>
+Maybe<T>::Maybe(const T& value)
+: mNothing(false) {
+ new (&mStorage) T(value);
+}
+
+template <typename T>
+Maybe<T>::Maybe(T&& value)
+: mNothing(false) {
+ new (&mStorage) T(std::forward<T>(value));
+}
+
+template <typename T>
+Maybe<T>::operator bool() const {
+ return !mNothing;
+}
+
+template <typename T>
+T& Maybe<T>::value() {
+ assert(!mNothing && "Maybe<T>::value() called on Nothing");
+ return reinterpret_cast<T&>(mStorage);
+}
+
+template <typename T>
+const T& Maybe<T>::value() const {
+ assert(!mNothing && "Maybe<T>::value() called on Nothing");
+ return reinterpret_cast<const T&>(mStorage);
+}
+
+template <typename T>
+void Maybe<T>::destroy() {
+ reinterpret_cast<T&>(mStorage).~T();
+}
+
+template <typename T>
+inline Maybe<typename std::remove_reference<T>::type> make_value(T&& value) {
+ return Maybe<typename std::remove_reference<T>::type>(std::forward<T>(value));
+}
+
+template <typename T>
+inline Maybe<T> make_nothing() {
+ return Maybe<T>();
+}
+
+} // namespace aapt
+
+#endif // AAPT_MAYBE_H