network: implement net_select() for the Wii (#192)

poll() is generally more efficient and does not have a limitation on the
number of file descriptors, but many libraries and programs out there
still use select(), so let's make it easier to port them too

libogc/network_wii.c

@@ -992,8 +992,54 @@ s32 net_close(s32 s)
 
 s32 net_select(s32 maxfdp1, fd_set *readset, fd_set *writeset, fd_set *exceptset, struct timeval *timeout)
 {
-	// not yet implemented
-	return -EINVAL;
+	struct pollsd sds[FD_SETSIZE];
+	int i, n_sds = 0;
+	s32 timeout_msecs;
+	s32 ret;
+
+	memset(sds, 0, sizeof(sds));
+	for (i = 0; i < maxfdp1; i++) {
+		bool watched = false;
+
+		if (readset && FD_ISSET(i, readset)) {
+			sds[n_sds].events |= POLLIN;
+			watched = true;
+		}
+		if (writeset && FD_ISSET(i, writeset)) {
+			sds[n_sds].events |= POLLOUT;
+			watched = true;
+		}
+		if (exceptset && FD_ISSET(i, exceptset)) {
+			sds[n_sds].events |= POLLPRI;
+			watched = true;
+		}
+
+		if (watched) {
+			sds[n_sds++].socket = i;
+		}
+	}
+
+	timeout_msecs = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;
+	ret = net_poll(sds, n_sds, timeout_msecs);
+	if (ret <= 0) return ret;
+
+	ret = 0; /* Return the total number of 1 bits in the three fd sets */
+	for (i = 0; i < n_sds; i++) {
+		u8 fd = sds[i].socket;
+		if (sds[i].events & POLLIN) {
+			if (sds[i].revents & POLLIN) ret++;
+			else FD_CLR(fd, readset);
+		}
+		if (sds[i].events & POLLOUT) {
+			if (sds[i].revents & POLLOUT) ret++;
+			else FD_CLR(fd, writeset);
+		}
+		if (sds[i].events & POLLPRI) {
+			if (sds[i].revents & (POLLERR | POLLPRI | POLLHUP)) ret++;
+			else FD_CLR(fd, exceptset);
+		}
+	}
+	return ret;
 }
 
 s32 net_getsockname(s32 s, struct sockaddr *name, socklen_t *namelen)