gst: share the core between connections

Make all sources in the same process with the same fd share the
connection to the server. This makes it possible to set the same
fd on multiple sources/sinks and have them all use the same
connection, like when capturing multiple monitors from screencast
with the portal.

Fixes #241

src/gst/gstpipewirecore.c

@@ -0,0 +1,191 @@
+/* GStreamer
+ *
+ * Copyright © 2020 Wim Taymans
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+#include <unistd.h>
+
+#include <spa/utils/result.h>
+
+#include "gstpipewirecore.h"
+
+/* a list of global cores indexed by fd. */
+G_LOCK_DEFINE_STATIC (cores_lock);
+static GList *cores;
+
+static void
+on_core_error(void *data, uint32_t id, int seq, int res, const char *message)
+{
+  GstPipeWireCore *core = data;
+
+  pw_log_error("error id:%u seq:%d res:%d (%s): %s",
+          id, seq, res, spa_strerror(res), message);
+
+  if (id == PW_ID_CORE) {
+    core->last_error = res;
+  }
+  pw_thread_loop_signal(core->loop, FALSE);
+}
+
+static void on_core_done (void *object, uint32_t id, int seq)
+{
+  GstPipeWireCore * core = object;
+  if (id == PW_ID_CORE) {
+    core->last_seq = seq;
+    pw_thread_loop_signal (core->loop, FALSE);
+  }
+}
+
+static const struct pw_core_events core_events = {
+  PW_VERSION_CORE_EVENTS,
+  .done = on_core_done,
+  .error = on_core_error,
+};
+
+static GstPipeWireCore *make_core (int fd)
+{
+  GstPipeWireCore *core;
+
+  core = g_new (GstPipeWireCore, 1);
+  core->refcount = 1;
+  core->fd = fd;
+  core->loop = pw_thread_loop_new ("pipewire-main-loop", NULL);
+  core->context = pw_context_new (pw_thread_loop_get_loop(core->loop), NULL, 0);
+  GST_DEBUG ("loop %p context %p", core->loop, core->context);
+
+  if (pw_thread_loop_start (core->loop) < 0)
+    goto mainloop_failed;
+
+  pw_thread_loop_lock (core->loop);
+
+  if (fd == -1)
+    core->core = pw_context_connect (core->context, NULL, 0);
+  else
+    core->core = pw_context_connect_fd (core->context, dup(fd), NULL, 0);
+
+  if (core->core == NULL)
+    goto connection_failed;
+
+  pw_core_add_listener(core->core,
+                       &core->core_listener,
+                       &core_events,
+                       core);
+
+  pw_thread_loop_unlock (core->loop);
+
+  return core;
+
+mainloop_failed:
+  {
+    GST_ERROR ("error starting mainloop");
+    return NULL;
+  }
+connection_failed:
+  {
+    GST_ERROR ("error connect: %m");
+    pw_thread_loop_unlock (core->loop);
+    return NULL;
+  }
+}
+
+typedef struct {
+  int fd;
+} FindData;
+
+static gint
+core_find (GstPipeWireCore * core, FindData * data)
+{
+  /* fd's must match */
+  if (core->fd == data->fd)
+    return 0;
+  return 1;
+}
+
+GstPipeWireCore *gst_pipewire_core_get (int fd)
+{
+  GstPipeWireCore *core;
+  FindData data;
+  GList *found;
+
+  data.fd = fd;
+
+  G_LOCK (cores_lock);
+  found = g_list_find_custom (cores, &data, (GCompareFunc) core_find);
+  if (found != NULL) {
+    core = (GstPipeWireCore *) found->data;
+    core->refcount++;
+    GST_DEBUG ("found core %p", core);
+  } else {
+    core = make_core(fd);
+    if (core != NULL) {
+      GST_DEBUG ("created core %p", core);
+      /* add to list on success */
+      cores = g_list_prepend (cores, core);
+    } else {
+      GST_WARNING ("could not create core");
+    }
+  }
+  G_UNLOCK (cores_lock);
+
+  return core;
+}
+
+static void do_sync(GstPipeWireCore * core)
+{
+  core->pending_seq = pw_core_sync(core->core, 0, core->pending_seq);
+  while (true) {
+    if (core->last_seq == core->pending_seq || core->last_error < 0)
+      break;
+    pw_thread_loop_wait (core->loop);
+  }
+}
+
+void gst_pipewire_core_release (GstPipeWireCore *core)
+{
+  gboolean zero;
+
+  G_LOCK (cores_lock);
+  core->refcount--;
+  if ((zero = (core->refcount == 0))) {
+    GST_DEBUG ("closing core %p", core);
+    /* remove from list, we can release the mutex after removing the connection
+     * from the list because after that, nobody can access the connection anymore. */
+    cores = g_list_remove (cores, core);
+  }
+  G_UNLOCK (cores_lock);
+
+  if (zero) {
+    pw_thread_loop_lock (core->loop);
+    do_sync(core);
+
+    pw_core_disconnect (core->core);
+    pw_thread_loop_unlock (core->loop);
+    pw_thread_loop_stop (core->loop);
+    pw_context_destroy (core->context);
+    pw_thread_loop_destroy (core->loop);
+
+    free(core);
+  }
+}