1 files changed, 88 insertions, 0 deletions
diff --git a/services/surfaceflinger/tests/unittests/PromiseTest.cpp b/services/surfaceflinger/tests/unittests/PromiseTest.cpp
new file mode 100644
index 0000000000..e4dc1fedb1
--- /dev/null
+++ b/services/surfaceflinger/tests/unittests/PromiseTest.cpp
@@ -0,0 +1,88 @@
+/*
+ * 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 <algorithm>
+#include <future>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include "Promise.h"
+
+namespace android {
+namespace {
+
+using Bytes = std::vector<uint8_t>;
+
+Bytes decrement(Bytes bytes) {
+    std::transform(bytes.begin(), bytes.end(), bytes.begin(), [](auto b) { return b - 1; });
+    return bytes;
+}
+
+} // namespace
+
+TEST(PromiseTest, yield) {
+    EXPECT_EQ(42, promise::yield(42).get());
+
+    auto ptr = std::make_unique<char>('!');
+    auto future = promise::yield(std::move(ptr));
+    EXPECT_EQ('!', *future.get());
+}
+
+TEST(PromiseTest, chain) {
+    std::packaged_task<const char*()> fetchString([] { return "ifmmp-"; });
+
+    std::packaged_task<Bytes(std::string)> appendString([](std::string str) {
+        str += "!xpsme";
+        return Bytes{str.begin(), str.end()};
+    });
+
+    std::packaged_task<std::future<Bytes>(Bytes)> decrementBytes(
+            [](Bytes bytes) { return promise::defer(decrement, std::move(bytes)); });
+
+    auto fetch = fetchString.get_future();
+    std::thread fetchThread(std::move(fetchString));
+
+    std::thread appendThread, decrementThread;
+
+    EXPECT_EQ("hello, world",
+              promise::chain(std::move(fetch))
+                      .then([](const char* str) { return std::string(str); })
+                      .then([&](std::string str) {
+                          auto append = appendString.get_future();
+                          appendThread = std::thread(std::move(appendString), std::move(str));
+                          return append;
+                      })
+                      .then([&](Bytes bytes) {
+                          auto decrement = decrementBytes.get_future();
+                          decrementThread = std::thread(std::move(decrementBytes),
+                                                        std::move(bytes));
+                          return decrement;
+                      })
+                      .then([](std::future<Bytes> bytes) { return bytes; })
+                      .then([](const Bytes& bytes) {
+                          return std::string(bytes.begin(), bytes.end());
+                      })
+                      .get());
+
+    fetchThread.join();
+    appendThread.join();
+    decrementThread.join();
+}
+
+} // namespace android