FTL: Import std::future utilities from SF
Now including docs and expanded tests.
Bug: 160012986
Test: ftl_test
Change-Id: If9eb25646bb33ebc417ea87e6718b46fe0b87cf3
diff --git a/libs/ftl/future_test.cpp b/libs/ftl/future_test.cpp
new file mode 100644
index 0000000..9b3e936
--- /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