shmsink: add an shm-area-name property

The shm-area-property tells the name of the shm area used by the element. This
is useful for cases where shmsink is not able to clean up (calling
shm_unlink()), e.g. if it is in a sandbox.

https://bugzilla.gnome.org/show_bug.cgi?id=675134

sys/shm/gstshmsrc.c

@@ -54,7 +54,8 @@ enum
 {
   PROP_0,
   PROP_SOCKET_PATH,
-  PROP_IS_LIVE
+  PROP_IS_LIVE,
+  PROP_SHM_AREA_NAME
 };
 
 struct GstShmBuffer
@@ -123,14 +124,20 @@ gst_shm_src_class_init (GstShmSrcClass * klass)
   g_object_class_install_property (gobject_class, PROP_SOCKET_PATH,
       g_param_spec_string ("socket-path",
           "Path to the control socket",
-          "The path to the control socket used to control the shared memory"
-          " transport", NULL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+          "The path to the control socket used to control the shared memory",
+          NULL, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
   g_object_class_install_property (gobject_class, PROP_IS_LIVE,
       g_param_spec_boolean ("is-live", "Is this a live source",
           "True if the element cannot produce data in PAUSED", FALSE,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  g_object_class_install_property (gobject_class, PROP_SHM_AREA_NAME,
+      g_param_spec_string ("shm-area-name",
+          "Name of the shared memory area",
+          "The name of the shared memory area used to get buffers",
+          NULL, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
+
   gst_element_class_add_pad_template (gstelement_class,
       gst_static_pad_template_get (&srctemplate));
 
@@ -205,6 +212,12 @@ gst_shm_src_get_property (GObject * object, guint prop_id,
     case PROP_IS_LIVE:
       g_value_set_boolean (value, gst_base_src_is_live (GST_BASE_SRC (object)));
       break;
+    case PROP_SHM_AREA_NAME:
+      GST_OBJECT_LOCK (object);
+      if (self->pipe)
+        g_value_set_string (value, sp_get_shm_area_name (self->pipe->pipe));
+      GST_OBJECT_UNLOCK (object);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;

sys/shm/shmpipe.c

@@ -90,6 +90,7 @@ struct _ShmArea
   int id;
 
   int use_count;
+  int is_writer;
 
   int shm_fd;
 
@@ -286,6 +287,8 @@ sp_open_shm (char *path, int id, mode_t perms, size_t size)
 
   area->shm_area_len = size;
 
+  area->is_writer = (path == NULL);
+
 
   if (path)
     flags = O_RDONLY;
@@ -320,6 +323,7 @@ sp_open_shm (char *path, int id, mode_t perms, size_t size)
 
     prot = PROT_READ | PROT_WRITE;
   } else {
+    area->shm_area_name = strdup (path);
     prot = PROT_READ;
   }
 
@@ -353,7 +357,8 @@ sp_close_shm (ShmArea * area)
     close (area->shm_fd);
 
   if (area->shm_area_name) {
-    shm_unlink (area->shm_area_name);
+    if (area->is_writer)
+      shm_unlink (area->shm_area_name);
     free (area->shm_area_name);
   }
 
@@ -935,6 +940,15 @@ sp_get_fd (ShmPipe * self)
   return self->main_socket;
 }
 
+const gchar *
+sp_get_shm_area_name (ShmPipe * self)
+{
+  if (self->shm_area)
+    return self->shm_area->shm_area_name;
+
+  return NULL;
+}
+
 int
 sp_writer_get_client_fd (ShmClient * client)
 {

sys/shm/shmpipe.h

@@ -91,6 +91,7 @@ int sp_writer_setperms_shm (ShmPipe * self, mode_t perms);
 int sp_writer_resize (ShmPipe * self, size_t size);
 
 int sp_get_fd (ShmPipe * self);
+const char *sp_get_shm_area_name (ShmPipe *self);
 int sp_writer_get_client_fd (ShmClient * client);
 
 ShmBlock *sp_writer_alloc_block (ShmPipe * self, size_t size);