windows: Add examples/csp_server_client_windows.c

csp_server_client requires arch specific thread creation functions.
With xamples/csp_server_client_windows.c, csp_server_client can now be
compiled for Windows.

I use uintptr_t for the return variable because it what
_beginthreadex() returns. We don't have anything to pass to the
function except the thread entry function.

The wrapper was using 0 for the last parameter but it's actually a
pointer to an unsigned int. So I've changed it to NULL. That's what
the doc says:

https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/beginthread-beginthreadex

    thrdaddr

    Points to a 32-bit variable that receives the thread
    identifier. If it's NULL, it's not used.

Signed-off-by: Yasushi SHOJI <[email protected]>

Author: yashi

examples/csp_server_client_windows.c

@@ -0,0 +1,48 @@
+#include <csp/csp.h>
+#include <windows.h>
+#include <process.h>
+
+void server(void);
+void client(void);
+
+static int csp_win_thread_create(unsigned int (* routine)(void *)) {
+
+	uintptr_t ret = _beginthreadex(NULL, 0, routine, NULL, 0, NULL);
+	if (ret == 0) {
+		return CSP_ERR_NOMEM;
+	}
+
+	return CSP_ERR_NONE;
+}
+
+static unsigned int task_router(void * param) {
+
+	/* Here there be routing */
+	while (1) {
+		csp_route_work();
+	}
+
+	return 0;
+}
+
+static unsigned int task_server(void * param) {
+	server();
+	return 0;
+}
+
+static unsigned int task_client(void * param) {
+	client();
+	return 0;
+}
+
+int router_start(void) {
+	return csp_win_thread_create(task_router);
+}
+
+int server_start(void) {
+	return csp_win_thread_create(task_server);
+}
+
+int client_start(void) {
+	return csp_win_thread_create(task_client);
+}