upnp: initialize the client handle only once

Eliminate class LibUPnP and move the code to ClientInit.cxx.  Its
initialization function can be called multiple times, but
UpnpRegisterClient() is called at most once.

src/lib/upnp/ClientInit.cxx

@@ -18,31 +18,21 @@
  */
 
 #include "config.h"
-#include "upnpplib.hxx"
+#include "ClientInit.hxx"
+#include "Init.hxx"
 #include "Callback.hxx"
 #include "Domain.hxx"
-#include "Init.hxx"
-#include "Log.hxx"
+#include "thread/Mutex.hxx"
+#include "util/Error.hxx"
 
 #include <upnp/upnptools.h>
 
-LibUPnP::LibUPnP()
-{
-	if (!UpnpGlobalInit(init_error))
-		return;
+static Mutex upnp_client_init_mutex;
+static unsigned upnp_client_ref;
+static UpnpClient_Handle upnp_client_handle;
 
-	auto code = UpnpRegisterClient(o_callback, nullptr, &m_clh);
-	if (code != UPNP_E_SUCCESS) {
-		UpnpGlobalFinish();
-		init_error.Format(upnp_domain, code,
-				  "UpnpRegisterClient() failed: %s",
-				  UpnpGetErrorMessage(code));
-		return;
-	}
-}
-
-int
-LibUPnP::o_callback(Upnp_EventType et, void* evp, void* cookie)
+static int
+UpnpClientCallback(Upnp_EventType et, void *evp, void *cookie)
 {
 	if (cookie == nullptr)
 		/* this is the cookie passed to UpnpRegisterClient();
@@ -54,7 +44,50 @@ LibUPnP::o_callback(Upnp_EventType et, void* evp, void* cookie)
 	return callback.Invoke(et, evp);
 }
 
-LibUPnP::~LibUPnP()
+static bool
+DoInit(Error &error)
 {
+	auto code = UpnpRegisterClient(UpnpClientCallback, nullptr,
+				       &upnp_client_handle);
+	if (code != UPNP_E_SUCCESS) {
+		error.Format(upnp_domain, code,
+			     "UpnpRegisterClient() failed: %s",
+			     UpnpGetErrorMessage(code));
+		return false;
+	}
+
+	return true;
+}
+
+bool
+UpnpClientGlobalInit(UpnpClient_Handle &handle, Error &error)
+{
+	if (!UpnpGlobalInit(error))
+		return false;
+
+	upnp_client_init_mutex.lock();
+	bool success = upnp_client_ref > 0 || DoInit(error);
+	upnp_client_init_mutex.unlock();
+
+	if (success) {
+		++upnp_client_ref;
+		handle = upnp_client_handle;
+	} else
+		UpnpGlobalFinish();
+
+	return success;
+}
+
+void
+UpnpClientGlobalFinish()
+{
+	upnp_client_init_mutex.lock();
+
+	assert(upnp_client_ref > 0);
+	if (--upnp_client_ref == 0)
+		UpnpUnRegisterClient(upnp_client_handle);
+
+	upnp_client_init_mutex.unlock();
+
 	UpnpGlobalFinish();
 }

src/lib/upnp/ClientInit.hxx

@@ -17,43 +17,19 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#ifndef _LIBUPNP_H_X_INCLUDED_
-#define _LIBUPNP_H_X_INCLUDED_
+#ifndef MPD_UPNP_CLIENT_INIT_HXX
+#define MPD_UPNP_CLIENT_INIT_HXX
 
-#include "util/Error.hxx"
+#include "check.h"
 
 #include <upnp/upnp.h>
 
-/** Our link to libupnp. Initialize and keep the handle around */
-class LibUPnP {
-	Error init_error;
-	UpnpClient_Handle m_clh;
+class Error;
 
-	static int o_callback(Upnp_EventType, void *, void *);
+bool
+UpnpClientGlobalInit(UpnpClient_Handle &handle, Error &error);
 
-public:
-	LibUPnP();
+void
+UpnpClientGlobalFinish();
 
-	LibUPnP(const LibUPnP &) = delete;
-	LibUPnP &operator=(const LibUPnP &) = delete;
-
-	~LibUPnP();
-
-	/** Check state after initialization */
-	bool ok() const
-	{
-		return !init_error.IsDefined();
-	}
-
-	/** Retrieve init error if state not ok */
-	const Error &GetInitError() const {
-		return init_error;
-	}
-
-	UpnpClient_Handle getclh()
-	{
-		return m_clh;
-	}
-};
-
-#endif /* _LIBUPNP.H_X_INCLUDED_ */
+#endif