[sysprof] libsysprof-capture: write final frame

[Christian Hergert <chergert src gnome org>]

commit c36420d71641937ef7d39ddbe7e43f4f42e0812b
Author: Christian Hergert <chergert redhat com>
Date:   Sat Feb 15 20:49:27 2020 -0700

    libsysprof-capture: write final frame
    
    This frame type can be used to communicate with the peer over the mapped
    ring buffer to denote that writing is finished and it can free any
    resources for the mapping.

 src/libsysprof-capture/sysprof-collector.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)
---
diff --git a/src/libsysprof-capture/sysprof-collector.c b/src/libsysprof-capture/sysprof-collector.c
index 5694cc9..eac09ca 100644
--- a/src/libsysprof-capture/sysprof-collector.c
+++ b/src/libsysprof-capture/sysprof-collector.c
@@ -184,6 +184,24 @@ request_writer (void)
   return g_steal_pointer (&buffer);
 }
 
+static void
+write_final_frame (MappedRingBuffer *ring)
+{
+  SysprofCaptureFrame *fr;
+
+  g_assert (ring != NULL);
+
+  if ((fr = mapped_ring_buffer_allocate (ring, sizeof *fr)))
+    {
+      fr->len = sizeof *fr; /* aligned */
+      fr->type = 0xFF;      /* Invalid */
+      fr->cpu = -1;
+      fr->pid = -1;
+      fr->time = SYSPROF_CAPTURE_CURRENT_TIME;
+      mapped_ring_buffer_advance (ring, fr->len);
+    }
+}
+
 static void
 sysprof_collector_free (gpointer data)
 {
@@ -191,7 +209,12 @@ sysprof_collector_free (gpointer data)
 
   if (collector != NULL && collector != COLLECTOR_MAGIC_CREATING)
     {
-      g_clear_pointer (&collector->buffer, mapped_ring_buffer_unref);
+      if (collector->buffer != NULL)
+        {
+          write_final_frame (collector->buffer);
+          g_clear_pointer (&collector->buffer, mapped_ring_buffer_unref);
+        }
+
       g_free (collector);
     }
 }