Fix benchmark test problem on Windows

Author: yhirose

httplib.h

@@ -3246,8 +3246,11 @@ inline int poll_wrapper(struct pollfd *fds, nfds_t nfds, int timeout) {
 
 template <bool Read>
 inline ssize_t select_impl(socket_t sock, time_t sec, time_t usec) {
+#if defined(__APPLE__) || defined(_WIN32)
+  // Use select() on macOS and Windows for better performance
 #ifdef __APPLE__
   if (sock >= FD_SETSIZE) { return -1; }
+#endif
 
   fd_set fds, *rfds, *wfds;
   FD_ZERO(&fds);
@@ -3260,9 +3263,15 @@ inline ssize_t select_impl(socket_t sock, time_t sec, time_t usec) {
   tv.tv_usec = static_cast<decltype(tv.tv_usec)>(usec);
 
   return handle_EINTR([&]() {
+#ifdef _WIN32
+    // On Windows, the first parameter of select() is ignored
+    return select(0, rfds, wfds, nullptr, &tv);
+#else
     return select(static_cast<int>(sock + 1), rfds, wfds, nullptr, &tv);
+#endif
   });
 #else
+  // Use poll() on Linux and other POSIX systems
   struct pollfd pfd;
   pfd.fd = sock;
   pfd.events = (Read ? POLLIN : POLLOUT);
@@ -3283,25 +3292,43 @@ inline ssize_t select_write(socket_t sock, time_t sec, time_t usec) {
 
 inline Error wait_until_socket_is_ready(socket_t sock, time_t sec,
                                         time_t usec) {
+#if defined(__APPLE__) || defined(_WIN32)
+  // Use select() on macOS and Windows.
+  // WSAPoll() on Windows has known performance issues with localhost
+  // connections. See: https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
 #ifdef __APPLE__
+  // On macOS, check if socket descriptor exceeds FD_SETSIZE
   if (sock >= FD_SETSIZE) { return Error::Connection; }
+#endif
 
-  fd_set fdsr, fdsw;
+  fd_set fdsr, fdsw, fdse;
   FD_ZERO(&fdsr);
   FD_ZERO(&fdsw);
+  FD_ZERO(&fdse);
   FD_SET(sock, &fdsr);
   FD_SET(sock, &fdsw);
+  FD_SET(sock, &fdse);
 
   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);
+#ifdef _WIN32
+    // On Windows, the first parameter of select() is ignored
+    return select(0, &fdsr, &fdsw, &fdse, &tv);
+#else
+    return select(static_cast<int>(sock + 1), &fdsr, &fdsw, &fdse, &tv);
+#endif
   });
 
   if (ret == 0) { return Error::ConnectionTimeout; }
 
+  if (ret > 0 && (FD_ISSET(sock, &fdse))) {
+    // Socket has an exception (connection failed)
+    return Error::Connection;
+  }
+
   if (ret > 0 && (FD_ISSET(sock, &fdsr) || FD_ISSET(sock, &fdsw))) {
     auto error = 0;
     socklen_t len = sizeof(error);
@@ -3313,6 +3340,7 @@ inline Error wait_until_socket_is_ready(socket_t sock, time_t sec,
 
   return Error::Connection;
 #else
+  // Use poll() on Linux and other POSIX systems
   struct pollfd pfd_read;
   pfd_read.fd = sock;
   pfd_read.events = POLLIN | POLLOUT;