Remove macOS select() fallback (#2365)

* Remove macOS select() fallback

macOS has supported `poll` for a long time now, so there's no need for
the specific `select` code paths.

With this commit, we can successfully build on visionOS.

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

* Fix coding style

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

---------

Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>

httplib.h

@@ -4600,78 +4600,32 @@ inline int poll_wrapper(struct pollfd *fds, nfds_t nfds, int timeout) {
 #endif
 }
 
-template <bool Read>
-inline ssize_t select_impl(socket_t sock, time_t sec, time_t usec) {
-#ifdef __APPLE__
-  if (sock >= FD_SETSIZE) { return -1; }
-
-  fd_set fds, *rfds, *wfds;
-  FD_ZERO(&fds);
-  FD_SET(sock, &fds);
-  rfds = (Read ? &fds : nullptr);
-  wfds = (Read ? nullptr : &fds);
-
-  timeval tv;
-  tv.tv_sec = static_cast<long>(sec);
-  tv.tv_usec = static_cast<decltype(tv.tv_usec)>(usec);
-
-  return handle_EINTR([&]() {
-    return select(static_cast<int>(sock + 1), rfds, wfds, nullptr, &tv);
-  });
-#else
+inline ssize_t select_impl(socket_t sock, short events, time_t sec,
+                           time_t usec) {
   struct pollfd pfd;
   pfd.fd = sock;
-  pfd.events = (Read ? POLLIN : POLLOUT);
+  pfd.events = events;
+  pfd.revents = 0;
 
   auto timeout = static_cast<int>(sec * 1000 + usec / 1000);
 
   return handle_EINTR([&]() { return poll_wrapper(&pfd, 1, timeout); });
-#endif
 }
 
 inline ssize_t select_read(socket_t sock, time_t sec, time_t usec) {
-  return select_impl<true>(sock, sec, usec);
+  return select_impl(sock, POLLIN, sec, usec);
 }
 
 inline ssize_t select_write(socket_t sock, time_t sec, time_t usec) {
-  return select_impl<false>(sock, sec, usec);
+  return select_impl(sock, POLLOUT, sec, usec);
 }
 
 inline Error wait_until_socket_is_ready(socket_t sock, time_t sec,
                                         time_t usec) {
-#ifdef __APPLE__
-  if (sock >= FD_SETSIZE) { return Error::Connection; }
-
-  fd_set fdsr, fdsw;
-  FD_ZERO(&fdsr);
-  FD_ZERO(&fdsw);
-  FD_SET(sock, &fdsr);
-  FD_SET(sock, &fdsw);
-
-  timeval tv;
-  tv.tv_sec = static_cast<long>(sec);
-  tv.tv_usec = static_cast<decltype(tv.tv_usec)>(usec);
-
-  auto ret = handle_EINTR([&]() {
-    return select(static_cast<int>(sock + 1), &fdsr, &fdsw, nullptr, &tv);
-  });
-
-  if (ret == 0) { return Error::ConnectionTimeout; }
-
-  if (ret > 0 && (FD_ISSET(sock, &fdsr) || FD_ISSET(sock, &fdsw))) {
-    auto error = 0;
-    socklen_t len = sizeof(error);
-    auto res = getsockopt(sock, SOL_SOCKET, SO_ERROR,
-                          reinterpret_cast<char *>(&error), &len);
-    auto successful = res >= 0 && !error;
-    return successful ? Error::Success : Error::Connection;
-  }
-
-  return Error::Connection;
-#else
   struct pollfd pfd_read;
   pfd_read.fd = sock;
   pfd_read.events = POLLIN | POLLOUT;
+  pfd_read.revents = 0;
 
   auto timeout = static_cast<int>(sec * 1000 + usec / 1000);
 
@@ -4690,7 +4644,6 @@ inline Error wait_until_socket_is_ready(socket_t sock, time_t sec,
   }
 
   return Error::Connection;
-#endif
 }
 
 inline bool is_socket_alive(socket_t sock) {
@@ -10474,17 +10427,6 @@ Server::process_request(Stream &strm, const std::string &remote_addr,
   res.version = "HTTP/1.1";
   res.headers = default_headers_;
 
-#ifdef __APPLE__
-  // Socket file descriptor exceeded FD_SETSIZE...
-  if (strm.socket() >= FD_SETSIZE) {
-    Headers dummy;
-    detail::read_headers(strm, dummy);
-    res.status = StatusCode::InternalServerError_500;
-    output_error_log(Error::ExceedMaxSocketDescriptorCount, &req);
-    return write_response(strm, close_connection, req, res);
-  }
-#endif
-
   // Request line and headers
   if (!parse_request_line(line_reader.ptr(), req)) {
     res.status = StatusCode::BadRequest_400;