From c992dd2184b986fab2c2888bbe5197a6d7366300 Mon Sep 17 00:00:00 2001
From: Seungha Yang <seungha@centricular.com>
Date: Sat, 12 Aug 2023 00:58:10 +0900
Subject: [PATCH] wasapi2ringbuffer: Don't use GLib's weak pointer
 implementation

GWeakRef takes global mutex. Use C++ weak_ptr which will perform
atomic operation internally.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5176>
---
 .../sys/wasapi2/gstwasapi2ringbuffer.cpp      | 52 +++++++++++++------
 1 file changed, 36 insertions(+), 16 deletions(-)

diff --git a/subprojects/gst-plugins-bad/sys/wasapi2/gstwasapi2ringbuffer.cpp b/subprojects/gst-plugins-bad/sys/wasapi2/gstwasapi2ringbuffer.cpp
index 8069d333a0..f60eca9542 100644
--- a/subprojects/gst-plugins-bad/sys/wasapi2/gstwasapi2ringbuffer.cpp
+++ b/subprojects/gst-plugins-bad/sys/wasapi2/gstwasapi2ringbuffer.cpp
@@ -21,6 +21,7 @@
 #include <string.h>
 #include <mfapi.h>
 #include <wrl.h>
+#include <memory>
 
 GST_DEBUG_CATEGORY_STATIC (gst_wasapi2_ring_buffer_debug);
 #define GST_CAT_DEFAULT gst_wasapi2_ring_buffer_debug
@@ -32,22 +33,28 @@ gst_wasapi2_ring_buffer_loopback_callback (GstWasapi2RingBuffer * buf);
 /* *INDENT-OFF* */
 using namespace Microsoft::WRL;
 
+struct GstWasapi2RingBufferPtr
+{
+  GstWasapi2RingBufferPtr (GstWasapi2RingBuffer * ringbuffer)
+      : obj(ringbuffer)
+  {
+  }
+
+  /* Point to ringbuffer without holding ownership */
+  GstWasapi2RingBuffer *obj;
+};
+
 class GstWasapiAsyncCallback : public IMFAsyncCallback
 {
 public:
-  GstWasapiAsyncCallback(GstWasapi2RingBuffer *listener,
+  GstWasapiAsyncCallback(std::shared_ptr<GstWasapi2RingBufferPtr> listener,
                          DWORD queue_id,
                          gboolean loopback)
     : ref_count_(1)
     , queue_id_(queue_id)
+    , listener_(listener)
     , loopback_(loopback)
   {
-    g_weak_ref_init (&listener_, listener);
-  }
-
-  virtual ~GstWasapiAsyncCallback ()
-  {
-    g_weak_ref_set (&listener_, nullptr);
   }
 
   /* IUnknown */
@@ -108,20 +115,18 @@ public:
   STDMETHODIMP
   Invoke(IMFAsyncResult * pAsyncResult)
   {
-    GstWasapi2RingBuffer *ringbuffer;
     HRESULT hr;
+    auto ptr = listener_.lock ();
 
-    ringbuffer = (GstWasapi2RingBuffer *) g_weak_ref_get (&listener_);
-    if (!ringbuffer) {
+    if (!ptr) {
       GST_WARNING ("Listener was removed");
       return S_OK;
     }
 
     if (loopback_)
-      hr = gst_wasapi2_ring_buffer_loopback_callback (ringbuffer);
+      hr = gst_wasapi2_ring_buffer_loopback_callback (ptr->obj);
     else
-      hr = gst_wasapi2_ring_buffer_io_callback (ringbuffer);
-    gst_object_unref (ringbuffer);
+      hr = gst_wasapi2_ring_buffer_io_callback (ptr->obj);
 
     return hr;
   }
@@ -129,9 +134,14 @@ public:
 private:
   ULONG ref_count_;
   DWORD queue_id_;
-  GWeakRef listener_;
+  std::weak_ptr<GstWasapi2RingBufferPtr> listener_;
   gboolean loopback_;
 };
+
+struct GstWasapi2RingBufferPrivate
+{
+  std::shared_ptr<GstWasapi2RingBufferPtr> obj_ptr;
+};
 /* *INDENT-ON* */
 
 struct _GstWasapi2RingBuffer
@@ -179,6 +189,8 @@ struct _GstWasapi2RingBuffer
   gboolean monitor_device_mute;
 
   GstCaps *supported_caps;
+
+  GstWasapi2RingBufferPrivate *priv;
 };
 
 static void gst_wasapi2_ring_buffer_constructed (GObject * object);
@@ -239,6 +251,9 @@ gst_wasapi2_ring_buffer_init (GstWasapi2RingBuffer * self)
   self->event_handle = CreateEvent (nullptr, FALSE, FALSE, nullptr);
   self->loopback_event_handle = CreateEvent (nullptr, FALSE, FALSE, nullptr);
   g_mutex_init (&self->volume_lock);
+
+  self->priv = new GstWasapi2RingBufferPrivate ();
+  self->priv->obj_ptr = std::make_shared < GstWasapi2RingBufferPtr > (self);
 }
 
 static void
@@ -255,7 +270,8 @@ gst_wasapi2_ring_buffer_constructed (GObject * object)
     goto out;
   }
 
-  self->callback_object = new GstWasapiAsyncCallback (self, queue_id, FALSE);
+  self->callback_object = new GstWasapiAsyncCallback (self->priv->obj_ptr,
+      queue_id, FALSE);
   hr = MFCreateAsyncResult (nullptr, self->callback_object, nullptr,
       &self->callback_result);
   if (!gst_wasapi2_result (hr)) {
@@ -265,7 +281,7 @@ gst_wasapi2_ring_buffer_constructed (GObject * object)
 
   /* Create another callback object for loopback silence feed */
   self->loopback_callback_object =
-      new GstWasapiAsyncCallback (self, queue_id, TRUE);
+      new GstWasapiAsyncCallback (self->priv->obj_ptr, queue_id, TRUE);
   hr = MFCreateAsyncResult (nullptr, self->loopback_callback_object, nullptr,
       &self->loopback_callback_result);
   if (!gst_wasapi2_result (hr)) {
@@ -284,6 +300,8 @@ gst_wasapi2_ring_buffer_dispose (GObject * object)
 {
   GstWasapi2RingBuffer *self = GST_WASAPI2_RING_BUFFER (object);
 
+  self->priv->obj_ptr = nullptr;
+
   GST_WASAPI2_CLEAR_COM (self->render_client);
   GST_WASAPI2_CLEAR_COM (self->capture_client);
   GST_WASAPI2_CLEAR_COM (self->volume_object);
@@ -309,6 +327,8 @@ gst_wasapi2_ring_buffer_finalize (GObject * object)
   CloseHandle (self->loopback_event_handle);
   g_mutex_clear (&self->volume_lock);
 
+  delete self->priv;
+
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }