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333 lines (259 loc) · 8.85 KB
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export module mcpplibs.cmp:run_loop;
import std;
import :task;
namespace mcpplibs::cmp::detail {
struct RootCompletionBase {
bool completed_ { false };
std::exception_ptr exception_ {};
};
template<typename T>
struct RootCompletion final : RootCompletionBase {
std::optional<T> result_ {};
};
template<>
struct RootCompletion<void> final : RootCompletionBase {};
class RunLoopState final {
private:
std::mutex mutex_ {};
std::condition_variable condition_ {};
std::deque<std::coroutine_handle<>> ready_ {};
bool running_ { false };
public:
void begin_run() {
const std::lock_guard lock { mutex_ };
if (running_) {
throw std::logic_error { "run loop is already running" };
}
if (!ready_.empty()) {
throw std::logic_error { "run loop contains abandoned work" };
}
running_ = true;
}
void enqueue(std::coroutine_handle<> coroutine) {
if (!coroutine) {
throw std::invalid_argument { "cannot schedule an empty coroutine" };
}
{
const std::lock_guard lock { mutex_ };
if (!running_) {
throw std::logic_error { "scheduler has no active run" };
}
ready_.push_back(coroutine);
}
condition_.notify_one();
}
void complete(RootCompletionBase& completion) noexcept {
// 通过互斥量发布完成状态，以及此前写入的结果或异常
{
const std::lock_guard lock { mutex_ };
completion.completed_ = true;
}
condition_.notify_one();
}
void drive(RootCompletionBase& completion) {
while (true) {
std::coroutine_handle<> coroutine {};
{
std::unique_lock lock { mutex_ };
condition_.wait(lock, [&] {
return completion.completed_ || !ready_.empty();
});
if (completion.completed_) {
if (!ready_.empty()) {
throw std::logic_error {
"root task completed with outstanding work"
};
}
running_ = false;
return;
}
coroutine = ready_.front();
ready_.pop_front();
}
if (!coroutine || coroutine.done()) {
throw std::logic_error { "run loop contains a non-runnable coroutine" };
}
// 锁外恢复，协程再次入队时不会与 RunLoop 自锁
coroutine.resume();
}
}
void abort_run() noexcept {
const std::lock_guard lock { mutex_ };
ready_.clear();
running_ = false;
}
};
class RunGuard final {
private:
std::shared_ptr<RunLoopState> state_ {};
bool active_ { true };
public:
explicit RunGuard(std::shared_ptr<RunLoopState> state)
: state_ { std::move(state) } {
state_->begin_run();
}
RunGuard(const RunGuard&) = delete;
RunGuard& operator=(const RunGuard&) = delete;
RunGuard(RunGuard&&) = delete;
RunGuard& operator=(RunGuard&&) = delete;
~RunGuard() {
if (active_) {
state_->abort_run();
}
}
void release() noexcept {
active_ = false;
}
};
class RootOperation final {
public:
struct promise_type {
RunLoopState* state_ {};
RootCompletionBase* completion_ {};
[[nodiscard]] RootOperation get_return_object() noexcept;
[[nodiscard]] constexpr std::suspend_always initial_suspend() const noexcept {
return {};
}
class FinalAwaiter final {
public:
[[nodiscard]] constexpr bool await_ready() const noexcept {
return false;
}
void await_suspend(
std::coroutine_handle<promise_type> coroutine) const noexcept {
auto* const state = coroutine.promise().state_;
auto* const completion = coroutine.promise().completion_;
state->complete(*completion);
}
constexpr void await_resume() const noexcept {}
};
[[nodiscard]] constexpr FinalAwaiter final_suspend() const noexcept {
return {};
}
constexpr void return_void() const noexcept {}
void unhandled_exception() noexcept {
completion_->exception_ = std::current_exception();
}
};
private:
using Handle = std::coroutine_handle<promise_type>;
Handle coroutine_ {};
explicit RootOperation(Handle coroutine) noexcept
: coroutine_ { coroutine } {}
public:
RootOperation(const RootOperation&) = delete;
RootOperation& operator=(const RootOperation&) = delete;
RootOperation(RootOperation&& other) noexcept
: coroutine_ { std::exchange(other.coroutine_, {}) } {}
RootOperation& operator=(RootOperation&&) = delete;
~RootOperation() {
if (coroutine_) {
coroutine_.destroy();
}
}
void bind(RunLoopState& state, RootCompletionBase& completion) noexcept {
coroutine_.promise().state_ = &state;
coroutine_.promise().completion_ = &completion;
}
[[nodiscard]] std::coroutine_handle<> handle() const noexcept {
return coroutine_;
}
};
inline RootOperation RootOperation::promise_type::get_return_object() noexcept {
return RootOperation {
std::coroutine_handle<promise_type>::from_promise(*this)
};
}
template<typename T>
RootOperation make_root_operation(Task<T> task, RootCompletion<T>& completion) {
if constexpr (std::same_as<T, void>) {
co_await std::move(task);
} else {
completion.result_.emplace(co_await std::move(task));
}
}
} // namespace mcpplibs::cmp::detail
export namespace mcpplibs::cmp {
class RunLoop final {
public:
class Scheduler final {
private:
class ScheduleAwaiter final {
private:
std::weak_ptr<detail::RunLoopState> state_ {};
public:
explicit ScheduleAwaiter(
std::weak_ptr<detail::RunLoopState> state) noexcept
: state_ { std::move(state) } {}
[[nodiscard]] constexpr bool await_ready() const noexcept {
return false;
}
void await_suspend(std::coroutine_handle<> continuation) {
// 入队后协程可能立即恢复，因此先把状态保存到当前线程的栈上。
const auto state = state_.lock();
if (!state) {
throw std::logic_error { "scheduler's run loop no longer exists" };
}
state->enqueue(continuation);
}
constexpr void await_resume() const noexcept {}
};
std::weak_ptr<detail::RunLoopState> state_ {};
explicit Scheduler(
const std::shared_ptr<detail::RunLoopState>& state) noexcept
: state_ { state } {}
friend class RunLoop;
public:
Scheduler() = delete;
Scheduler(const Scheduler&) = default;
Scheduler& operator=(const Scheduler&) = default;
Scheduler(Scheduler&&) noexcept = default;
Scheduler& operator=(Scheduler&&) noexcept = default;
~Scheduler() = default;
[[nodiscard]] auto schedule() const noexcept {
return ScheduleAwaiter { state_ };
}
friend bool operator==(
const Scheduler& left,
const Scheduler& right) noexcept {
return !left.state_.owner_before(right.state_) &&
!right.state_.owner_before(left.state_);
}
};
private:
std::shared_ptr<detail::RunLoopState> state_ {
std::make_shared<detail::RunLoopState>()
};
public:
RunLoop() = default;
RunLoop(const RunLoop&) = delete;
RunLoop& operator=(const RunLoop&) = delete;
RunLoop(RunLoop&&) = delete;
RunLoop& operator=(RunLoop&&) = delete;
~RunLoop() = default;
[[nodiscard]] Scheduler get_scheduler() const noexcept {
return Scheduler { state_ };
}
template<typename T>
T run(Task<T> task) {
detail::RootCompletion<T> completion {};
detail::RunGuard guard { state_ };
auto operation = detail::make_root_operation(
std::move(task),
completion);
operation.bind(*state_, completion);
state_->enqueue(operation.handle());
state_->drive(completion);
guard.release();
if (completion.exception_) {
std::rethrow_exception(completion.exception_);
}
if constexpr (!std::same_as<T, void>) {
if (!completion.result_) {
throw std::logic_error { "root task completed without a result" };
}
return std::move(*completion.result_);
}
}
};
} // namespace mcpplibs::cmp