FTL: Add invariant for non-null pointers
Upcasting is not supported for now.
Bug: 185536303
Test: ftl_test
Change-Id: Id37d3e9a4a794291417405eb2a8a300a9d2bfe72
diff --git a/libs/ftl/non_null_test.cpp b/libs/ftl/non_null_test.cpp
new file mode 100644
index 0000000..bd0462b
--- /dev/null
+++ b/libs/ftl/non_null_test.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright 2022 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.
+ */
+
+#include <ftl/non_null.h>
+#include <gtest/gtest.h>
+
+#include <memory>
+#include <string>
+#include <string_view>
+
+namespace android::test {
+namespace {
+
+void get_length(const ftl::NonNull<std::shared_ptr<std::string>>& string_ptr,
+ ftl::NonNull<std::size_t*> length_ptr) {
+ // No need for `nullptr` checks.
+ *length_ptr = string_ptr->length();
+}
+
+using Pair = std::pair<ftl::NonNull<std::shared_ptr<int>>, std::shared_ptr<int>>;
+
+Pair dupe_if(ftl::NonNull<std::unique_ptr<int>> non_null_ptr, bool condition) {
+ // Move the underlying pointer out, so `non_null_ptr` must not be accessed after this point.
+ auto unique_ptr = std::move(non_null_ptr).take();
+
+ auto non_null_shared_ptr = ftl::as_non_null(std::shared_ptr<int>(std::move(unique_ptr)));
+ auto nullable_shared_ptr = condition ? non_null_shared_ptr.get() : nullptr;
+
+ return {std::move(non_null_shared_ptr), std::move(nullable_shared_ptr)};
+}
+
+} // namespace
+
+// Keep in sync with example usage in header file.
+TEST(NonNull, Example) {
+ const auto string_ptr = ftl::as_non_null(std::make_shared<std::string>("android"));
+ std::size_t size;
+ get_length(string_ptr, ftl::as_non_null(&size));
+ EXPECT_EQ(size, 7u);
+
+ auto ptr = ftl::as_non_null(std::make_unique<int>(42));
+ const auto [ptr1, ptr2] = dupe_if(std::move(ptr), true);
+ EXPECT_EQ(ptr1.get(), ptr2);
+}
+
+namespace {
+
+constexpr std::string_view kApple = "apple";
+constexpr std::string_view kOrange = "orange";
+
+using StringViewPtr = ftl::NonNull<const std::string_view*>;
+constexpr StringViewPtr kApplePtr = ftl::as_non_null(&kApple);
+constexpr StringViewPtr kOrangePtr = ftl::as_non_null(&kOrange);
+
+constexpr StringViewPtr longest(StringViewPtr ptr1, StringViewPtr ptr2) {
+ return ptr1->length() > ptr2->length() ? ptr1 : ptr2;
+}
+
+static_assert(longest(kApplePtr, kOrangePtr) == kOrangePtr);
+
+} // namespace
+} // namespace android::test