Spawn.hpp

#pragma once
 
#include <boost/asio/spawn.hpp>
#include <boost/asio/strand.hpp>
 
#include <concepts>
#include <exception>
#include <type_traits>
 
namespace util {
namespace impl {
 
template <typename T>
concept IsStrand = std::
    same_as<std::decay_t<T>, boost::asio::strand<typename std::decay_t<T>::inner_executor_type>>;

inline constexpr struct PropagatingCompletionHandler {
    void
    operator()(std::exception_ptr ePtr)
    {
        if (ePtr)
            std::rethrow_exception(ePtr);
    }
} kPROPAGATE_EXCEPTIONS;
 
}  // namespace impl

template <typename Ctx, typename F>
    requires std::is_invocable_r_v<void, F, boost::asio::yield_context>
void
spawn(Ctx&& ctx, F&& func)
{
    if constexpr (impl::IsStrand<Ctx>) {
        boost::asio::spawn(
            std::forward<Ctx>(ctx), std::forward<F>(func), impl::kPROPAGATE_EXCEPTIONS
        );
    } else {
        boost::asio::spawn(
            boost::asio::make_strand(std::forward<Ctx>(ctx).get_executor()),
            std::forward<F>(func),
            impl::kPROPAGATE_EXCEPTIONS
        );
    }
}
 
}  // namespace util