Add batch send and recv support #182
Description
I am integrating lsquic in our project, it need a user defined send callback function to send the data. In the c++ example, we could see lsquic_out_spec already build the data into iov, but currently xev.UDP.write only could pass slice or array. What is the best approach to use xev.UDP for this case. I thought one approach is transfering the iov copy into a slice and call xev.UDP.write though it need copy data.
api.ea_packets_out = +[](void *void_self,
const lsquic_out_spec *out_spec,
unsigned n_packets_out) {
auto self = static_cast<Engine *>(void_self);
// https://github.com/cbodley/nexus/blob/d1d8486f713fd089917331239d755932c7c8ed8e/src/socket.cc#L218
int r = 0;
for (auto &spec : std::span{out_spec, n_packets_out}) {
msghdr msg{};
msg.msg_iov = spec.iov;
msg.msg_iovlen = spec.iovlen;
// NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
msg.msg_name = const_cast<sockaddr *>(spec.dest_sa);
msg.msg_namelen = spec.dest_sa->sa_family == AF_INET
? sizeof(sockaddr_in)
: sizeof(sockaddr_in6);
auto n = sendmsg(self->socket_.native_handle(), &msg, 0);
if (n == -1) {
if (errno == EAGAIN or errno == EWOULDBLOCK) {
auto cb = [weak_self{self->weak_from_this()}](
boost::system::error_code ec) {
auto self = weak_self.lock();
if (not self) {
return;
}
if (ec) {
return;
}
lsquic_engine_send_unsent_packets(self->engine_);
};
self->socket_.async_wait(boost::asio::socket_base::wait_write,
std::move(cb));
}
break;
}
++r;
}
return r;
};