1 files changed, 105 insertions, 0 deletions
diff --git a/libs/ftl/future_test.cpp b/libs/ftl/future_test.cpp
new file mode 100644
index 0000000000..9b3e93683f
--- /dev/null
+++ b/libs/ftl/future_test.cpp
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2020 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/future.h>
+#include <gtest/gtest.h>
+
+#include <algorithm>
+#include <future>
+#include <string>
+#include <thread>
+#include <vector>
+
+namespace android::test {
+
+// Keep in sync with example usage in header file.
+TEST(Future, Example) {
+  {
+    auto future = ftl::defer([](int x) { return x + 1; }, 99);
+    EXPECT_EQ(future.get(), 100);
+  }
+  {
+    auto future = ftl::yield(42);
+    EXPECT_EQ(future.get(), 42);
+  }
+  {
+    auto ptr = std::make_unique<char>('!');
+    auto future = ftl::yield(std::move(ptr));
+    EXPECT_EQ(*future.get(), '!');
+  }
+  {
+    auto future = ftl::yield(123);
+    std::future<char> futures[] = {ftl::yield('a'), ftl::yield('b')};
+
+    std::future<char> chain = ftl::chain(std::move(future))
+                                  .then([](int x) { return static_cast<size_t>(x % 2); })
+                                  .then([&futures](size_t i) { return std::move(futures[i]); });
+
+    EXPECT_EQ(chain.get(), 'b');
+  }
+}
+
+namespace {
+
+using ByteVector = std::vector<uint8_t>;
+
+ByteVector decrement(ByteVector bytes) {
+  std::transform(bytes.begin(), bytes.end(), bytes.begin(), [](auto b) { return b - 1; });
+  return bytes;
+}
+
+}  // namespace
+
+TEST(Future, Chain) {
+  std::packaged_task<const char*()> fetch_string([] { return "ifmmp-"; });
+
+  std::packaged_task<ByteVector(std::string)> append_string([](std::string str) {
+    str += "!xpsme";
+    return ByteVector{str.begin(), str.end()};
+  });
+
+  std::packaged_task<std::future<ByteVector>(ByteVector)> decrement_bytes(
+      [](ByteVector bytes) { return ftl::defer(decrement, std::move(bytes)); });
+
+  auto fetch = fetch_string.get_future();
+  std::thread fetch_thread(std::move(fetch_string));
+
+  std::thread append_thread, decrement_thread;
+
+  EXPECT_EQ(
+      "hello, world",
+      ftl::chain(std::move(fetch))
+          .then([](const char* str) { return std::string(str); })
+          .then([&](std::string str) {
+            auto append = append_string.get_future();
+            append_thread = std::thread(std::move(append_string), std::move(str));
+            return append;
+          })
+          .then([&](ByteVector bytes) {
+            auto decrement = decrement_bytes.get_future();
+            decrement_thread = std::thread(std::move(decrement_bytes), std::move(bytes));
+            return decrement;
+          })
+          .then([](std::future<ByteVector> bytes) { return bytes; })
+          .then([](const ByteVector& bytes) { return std::string(bytes.begin(), bytes.end()); })
+          .get());
+
+  fetch_thread.join();
+  append_thread.join();
+  decrement_thread.join();
+}
+
+}  // namespace android::test