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/*
* Copyright 2019 Google LLC
*
* 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 "fcp/base/future.h"
#include <functional>
#include <memory>
#include <thread> // NOLINT(build/c++11)
#include <type_traits>
#include <utility>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/base/thread_annotations.h"
#include "absl/synchronization/barrier.h"
#include "absl/time/time.h"
#include "fcp/base/meta.h"
#include "fcp/base/move_to_lambda.h"
namespace fcp {
namespace thread {
using ::testing::Eq;
// Future::Wait and Future::Take sometimes block. We'd like to test thread
// interleavings where these calls block before being woken up. In the absence
// of instrumentation of the underlying synchronization primitives, we just use
// this arbitrary delay before unblocking operations (the other thread
// "probably" has time to block). Note that the other ordering (Promise::Set
// before Future::Take etc.) is easy to guarantee.
constexpr absl::Duration kArbitraryDelay = absl::Milliseconds(50);
void Delay() { absl::SleepFor(kArbitraryDelay); }
// Freely copyable test value. We put in a 'valid' value and hope to find it
// again.
enum class V { kInvalid, kValid };
// Move-only test value (we use this for Promise and Future, to make sure they
// are compatible with move-only types - typically the harder case). This
// corresponds to V:
// Value present (not moved) <=> kValid
// Value moved <=> kInvalid
// The TakeV / SetV wrappers below actually do those conversions, since the test
// assertions (e.g. Eq matcher) are difficult to use with move-only types.
using UV = UniqueValue<Unit>;
static_assert(!std::is_copy_constructible<UV>::value,
"Expected to be move-only");
std::optional<V> TakeV(Future<UV> future) {
std::optional<UV> maybe_uv = std::move(future).Take();
if (maybe_uv.has_value()) {
UniqueValue<Unit> uv = *std::move(maybe_uv);
return uv.has_value() ? V::kValid : V::kInvalid;
} else {
return std::nullopt;
}
}
void SetV(Promise<UV> promise) { std::move(promise).Set(UV(Unit{})); }
absl::Barrier MakeBarrier() { return absl::Barrier(2); }
void RunThreads(std::vector<std::function<void()>> fns) {
std::vector<std::thread> threads;
for (auto& fn : fns) {
threads.push_back(std::thread(std::move(fn)));
}
for (auto& thread : threads) {
thread.join();
}
}
void RunThreadsWithFuture(std::function<void(Promise<UV>)> promise_fn,
std::function<void(Future<UV>)> future_fn) {
FuturePair<UV> pair = MakeFuture<UV>();
MoveToLambdaWrapper<Promise<UV>> promise_capture =
MoveToLambda(std::move(pair.promise));
auto promise_fn_wrapped = [promise_capture, promise_fn]() mutable {
promise_fn(std::move(*promise_capture));
};
MoveToLambdaWrapper<Future<UV>> future_capture =
MoveToLambda(std::move(pair.future));
auto future_fn_wrapped = [future_capture, future_fn]() mutable {
future_fn(std::move(*future_capture));
};
RunThreads({std::move(promise_fn_wrapped), std::move(future_fn_wrapped)});
}
TEST(FutureTest, WaitTimeouts) {
absl::Barrier waited = MakeBarrier();
absl::Barrier set = MakeBarrier();
auto promise_fn = [&](Promise<UV> promise) {
waited.Block();
SetV(std::move(promise));
set.Block();
};
auto future_fn = [&](Future<UV> future) {
// Before set: Timeout should elapse
EXPECT_FALSE(future.Wait(absl::Milliseconds(1)))
<< "Future shouldn't be ready yet";
waited.Block();
set.Block();
// After set: Zero timeout should be sufficient
EXPECT_TRUE(future.Wait(absl::ZeroDuration()))
<< "Future should be ready without waiting";
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
TEST(FutureTest, TakeAfterSet) {
absl::Barrier set = MakeBarrier();
auto promise_fn = [&](Promise<UV> promise) {
SetV(std::move(promise));
set.Block();
};
auto future_fn = [&](Future<UV> future) {
set.Block();
EXPECT_THAT(TakeV(std::move(future)), Eq(V::kValid));
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
TEST(FutureTest, TakeProbablyBeforeSet) {
auto promise_fn = [](Promise<UV> promise) {
Delay();
SetV(std::move(promise));
};
auto future_fn = [](Future<UV> future) {
EXPECT_THAT(TakeV(std::move(future)), Eq(V::kValid));
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
TEST(FutureTest, AbandonWhileProbablyTaking) {
auto promise_fn = [](Promise<UV> promise) {
Delay();
{ Promise<UV> dies = std::move(promise); }
};
auto future_fn = [](Future<UV> future) {
EXPECT_THAT(std::move(future).Take(), Eq(std::nullopt));
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
TEST(FutureTest, SetWhileProbablyWaiting) {
auto promise_fn = [](Promise<UV> promise) {
Delay();
SetV(std::move(promise));
};
auto future_fn = [](Future<UV> future) {
EXPECT_TRUE(future.Wait(absl::InfiniteDuration()));
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
TEST(FutureTest, AbandonWhileProbablyWaiting) {
auto promise_fn = [](Promise<UV> promise) {
Delay();
{ Promise<UV> dies = std::move(promise); }
};
auto future_fn = [](Future<UV> future) {
EXPECT_TRUE(future.Wait(absl::InfiniteDuration()));
};
RunThreadsWithFuture(std::move(promise_fn), std::move(future_fn));
}
} // namespace thread
} // namespace fcp
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