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Support async::future::then

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This commit is contained in:
Nikita Lisitsa 2021-03-04 18:33:58 +03:00
parent dd32ab00d3
commit 1bfbaaa840
1 changed files with 112 additions and 9 deletions
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121
libs/async/include/psemek/async/future.hpp
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@ -38,6 +38,18 @@ namespace psemek::async
using type = bool;
};
template <typename T>
struct then_function
{
using type = util::function<void(T &)>;
};
template <>
struct then_function<void>
{
using type = util::function<void()>;
};
template <typename T>
struct task_state
{
@ -50,6 +62,9 @@ namespace psemek::async
std::condition_variable value_cv;
std::mutex then_mutex;
typename then_function<T>::type then_func;
task_state(bool auto_cancel)
: auto_cancel{auto_cancel}
{}
@ -159,6 +174,9 @@ namespace psemek::async
return wait_for(std::chrono::seconds{0});
}
template <typename F>
auto then(F && f);
private:
std::shared_ptr<detail::task_state<T>> state_;
@ -202,17 +220,25 @@ namespace psemek::async
void set_value(T const & value)
{
if (!state_) throw empty_promise_error{};
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = value;
{
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = value;
}
if (state_->then_func)
state_->then_func(*state_->value);
}
void set_value(T && value)
{
if (!state_) throw empty_promise_error{};
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = std::move(value);
{
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = std::move(value);
}
if (state_->then_func)
state_->then_func(*state_->value);
}
void set_exception(std::exception_ptr e)
@ -254,9 +280,13 @@ namespace psemek::async
void set_value()
{
if (!state_) throw empty_promise_error{};
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = true;
{
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception) throw satisfied_promise_error{};
state_->value = true;
}
if (state_->then_func)
state_->then_func();
}
void set_exception(std::exception_ptr e)
@ -333,4 +363,77 @@ namespace psemek::async
util::function<R(Args...)> func_;
};
template <typename T>
template <typename F>
auto future<T>::then(F && f)
{
if (!state_) throw empty_future_error{};
std::lock_guard lock{state_->value_mutex};
if (state_->value || state_->exception)
{
if constexpr (std::is_same_v<T, void>)
{
using R = decltype(f());
promise<R> p;
if (state_->value)
{
if constexpr (std::is_same_v<R, void>)
{
std::forward<F>(f)();
p.set_value();
}
else
{
p.set_value(std::forward<F>(f)());
}
}
else
p.set_exception(state_->exception);
return p.get_future();
}
else
{
using R = decltype(f(*(state_->value)));
promise<R> p;
if (state_->value)
{
if constexpr (std::is_same_v<R, void>)
{
std::forward<F>(f)(*(state_->value));
p.set_value();
}
else
{
p.set_value(std::forward<F>(f)(*(state_->value)));
}
}
else
p.set_exception(state_->exception);
return p.get_future();
}
}
if constexpr (std::is_same_v<T, void>)
{
using R = decltype(f());
packaged_task<R()> t(std::forward<F>(f));
std::lock_guard lock{state_->then_mutex};
state_->then_func = std::move(t);
return t.get_future();
}
else
{
using R = decltype(f(*(state_->value)));
packaged_task<R(T &)> t(std::forward<F>(f));
std::lock_guard lock{state_->then_mutex};
state_->then_func = std::move(t);
return t.get_future();
}
}
}