Struct CallbackAwaiter
Synopsis
#include <lib/inc/drogon/utils/coroutine.h>
template <typename T = void>
struct CallbackAwaiter
Description
Helper class that provides the infrastructure for turning callback into coroutines
Methods
| await_ready | ||
| await_resume | ||
| setException | ||
| setValue overload |
Source
Lines 491-531 in lib/inc/drogon/utils/coroutine.h.
template <typename T = void>
struct CallbackAwaiter
{
bool await_ready() noexcept
{
return false;
}
const T &await_resume() const noexcept(false)
{
// await_resume() should always be called after co_await
// (await_suspend()) is called. Therefore the value should always be set
// (or there's an exception)
assert(result_.has_value() == true || exception_ != nullptr);
if (exception_)
std::rethrow_exception(exception_);
return result_.value();
}
private:
// HACK: Not all desired types are default constructable. But we need the
// entire struct to be constructed for awaiting. std::optional takes care of
// that.
optional<T> result_;
std::exception_ptr exception_{nullptr};
protected:
void setException(const std::exception_ptr &e)
{
exception_ = e;
}
void setValue(const T &v)
{
result_.emplace(v);
}
void setValue(T &&v)
{
result_.emplace(std::move(v));
}
};