context: add helper object to manage events

Add a helper object to manage the events that define the context of a buffer and
a stream.

gst/Makefile.am

@@ -56,6 +56,7 @@ libgstreamer_@GST_MAJORMINOR@_la_SOURCES = \
 	gstcaps.c		\
 	gstchildproxy.c		\
 	gstclock.c		\
+	gstcontext.c		\
 	gstdatetime.c		\
 	gstdebugutils.c		\
 	gstelement.c		\
@@ -151,6 +152,7 @@ gst_headers =			\
 	gstchildproxy.h		\
 	gstclock.h		\
 	gstcompat.h		\
+	gstcontext.h		\
 	gstdatetime.h		\
 	gstdebugutils.h		\
 	gstelement.h		\

gst/gstcontext.c

@@ -0,0 +1,183 @@
+/* GStreamer
+ * Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * gstcontext.c: GstContext subsystem
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+/**
+ * SECTION:gstcontext
+ * @short_description: Structure containing events describing the context
+ *                     for buffers in a pipeline
+ * @see_also: #GstPad, #GstBuffer
+ *
+ * Last reviewed on 2011-05-4 (0.11.0)
+ */
+
+
+#include "gst_private.h"
+
+#include "gstinfo.h"
+#include "gstcontext.h"
+#include "gstutils.h"
+#include "gstquark.h"
+
+struct _GstContext
+{
+  GstMiniObject mini_object;
+
+  /*< private > */
+  GstEvent *events[GST_EVENT_MAX_STICKY];
+
+  gpointer _gst_reserved[GST_PADDING];
+};
+
+static GType _gst_context_type = 0;
+
+GType
+gst_context_get_type (void)
+{
+  if (G_UNLIKELY (_gst_context_type == 0)) {
+    _gst_context_type = gst_mini_object_register ("GstContext");
+  }
+  return _gst_context_type;
+}
+
+static void
+_gst_context_free (GstContext * context)
+{
+  g_return_if_fail (context != NULL);
+  g_return_if_fail (GST_IS_CONTEXT (context));
+
+  GST_LOG ("freeing context %p", context);
+
+  gst_context_clear (context);
+
+  g_slice_free1 (GST_MINI_OBJECT_SIZE (context), context);
+}
+
+static void gst_context_init (GstContext * context, gsize size);
+
+static GstContext *
+_gst_context_copy (GstContext * context)
+{
+  GstContext *copy;
+  guint i;
+
+  copy = g_slice_new0 (GstContext);
+
+  gst_context_init (copy, sizeof (GstContext));
+
+  for (i = 0; i < GST_EVENT_MAX_STICKY; i++)
+    gst_event_replace (&copy->events[i], context->events[i]);
+
+  return copy;
+}
+
+static void
+gst_context_init (GstContext * context, gsize size)
+{
+  gst_mini_object_init (GST_MINI_OBJECT_CAST (context), _gst_context_type,
+      size);
+
+  context->mini_object.copy = (GstMiniObjectCopyFunction) _gst_context_copy;
+  context->mini_object.free = (GstMiniObjectFreeFunction) _gst_context_free;
+}
+
+/**
+ * gst_context_new:
+ *
+ * Create a new #GstContext object that can be used to manage events.
+ *
+ * Returns: (transfer full): a new #GstContext
+ */
+GstContext *
+gst_context_new (void)
+{
+  GstContext *context;
+
+  context = g_slice_new0 (GstContext);
+
+  GST_DEBUG ("creating new context %p", context);
+
+  gst_context_init (context, sizeof (GstContext));
+
+  return context;
+}
+
+/**
+ * gst_context_update:
+ * @context: a #GstContext
+ * @event: a #GstEvent
+ *
+ * Update @context with @event. The context must be writable.
+ */
+void
+gst_context_update (GstContext * context, GstEvent * event)
+{
+  guint idx;
+
+  g_return_if_fail (context != NULL);
+  g_return_if_fail (gst_context_is_writable (context));
+
+  idx = GST_EVENT_STICKY_IDX (event);
+
+  GST_LOG ("storing event %s at index %u", GST_EVENT_TYPE_NAME (event), idx);
+
+  gst_event_replace (&context->events[idx], event);
+}
+
+/**
+ * gst_context_get:
+ * @context: a #GstContext
+ * @type: a #GstEventType
+ *
+ * Get the event of @type from @context.
+ *
+ * Returns: the last #GstEvent of @type that was updated on @context. This
+ * function returns NULL when there is no event with the given type.
+ */
+GstEvent *
+gst_context_get (GstContext * context, GstEventType type)
+{
+  guint idx;
+  GstEvent *event = NULL;
+
+  g_return_val_if_fail (context != NULL, NULL);
+
+  idx = GST_EVENT_STICKY_IDX_TYPE (type);
+
+  if ((event = context->events[idx]))
+    gst_event_ref (event);
+
+  return event;
+}
+
+/**
+ * gst_context_clear:
+ * @context: a #GstContext
+ *
+ * Clear all stored events in @context
+ */
+void
+gst_context_clear (GstContext * context)
+{
+  guint i;
+
+  for (i = 0; i < GST_EVENT_MAX_STICKY; i++)
+    gst_event_replace (&context->events[i], NULL);
+}

gst/gstcontext.h

@@ -0,0 +1,144 @@
+/* GStreamer
+ * Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.com>
+ *
+ * gstcontext.h: Header for GstContext subsystem
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+
+#ifndef __GST_CONTEXT_H__
+#define __GST_CONTEXT_H__
+
+#include <gst/gstminiobject.h>
+#include <gst/gstevent.h>
+
+G_BEGIN_DECLS
+
+#define GST_CONTEXT_TRACE_NAME    "GstContext"
+
+typedef struct _GstContext GstContext;
+
+#define GST_TYPE_CONTEXT                (gst_context_get_type())
+#define GST_IS_CONTEXT(obj)             (GST_IS_MINI_OBJECT_TYPE (obj, GST_TYPE_CONTEXT))
+#define GST_CONTEXT(obj)                ((GstContext *)(obj))
+#define GST_CONTEXT_CAST(obj)           ((GstContext *)(obj))
+
+
+/**
+ * gst_context_is_writable:
+ * @ctx: a #GstContext
+ *
+ * Tests if you can safely update @ctx with new events.
+ */
+#define         gst_context_is_writable(ctx)     gst_mini_object_is_writable (GST_MINI_OBJECT_CAST (ctx))
+
+/**
+ * gst_context_make_writable:
+ * @ctx: (transfer full): a #GstContext
+ *
+ * Makes a writable context from the given context. If the source context is
+ * already writable, this will simply return the same context. A copy will
+ * otherwise be made using gst_context_copy().
+ *
+ * Returns: (transfer full): a writable context which may or may not be the
+ *     same as @ctx
+ */
+#define         gst_context_make_writable(ctx)   GST_CONTEXT_CAST (gst_mini_object_make_writable (GST_MINI_OBJECT_CAST (buf)))
+
+/**
+ * gst_context_replace:
+ * @old_ctx: (inout) (transfer full): pointer to a pointer to a #GstContext
+ *     to be replaced.
+ * @new_ctx: (allow-none) (transfer none): pointer to a #GstContext that will
+ *     replace the context pointed to by @old_context.
+ *
+ * Modifies a pointer to a #GstContext to point to a different #GstContext. The
+ * modification is done atomically (so this is useful for ensuring thread safety
+ * in some cases), and the reference counts are updated appropriately (the old
+ * context is unreffed, the new one is reffed).
+ *
+ * Either @new_context or the #GstContext pointed to by @old_context may be NULL.
+ */
+#define         gst_context_replace(old_ctx,new_ctx) \
+    gst_mini_object_replace ((GstMiniObject **)(old_ctx), GST_MINI_OBJECT_CAST (new_ctx))
+
+GType           gst_context_get_type              (void);
+
+/* refcounting */
+/**
+ * gst_context_ref:
+ * @context: The context to refcount
+ *
+ * Increase the refcount of this context.
+ *
+ * Returns: (transfer full): @context (for convenience when doing assignments)
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC GstContext * gst_context_ref (GstContext * context);
+#endif
+
+static inline GstContext *
+gst_context_ref (GstContext * context)
+{
+  return (GstContext *) gst_mini_object_ref (GST_MINI_OBJECT_CAST (context));
+}
+
+/**
+ * gst_context_unref:
+ * @context: (transfer full): the context to refcount
+ *
+ * Decrease the refcount of an context, freeing it if the refcount reaches 0.
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC void gst_context_unref (GstContext * context);
+#endif
+
+static inline void
+gst_context_unref (GstContext * context)
+{
+  gst_mini_object_unref (GST_MINI_OBJECT_CAST (context));
+}
+
+/* copy context */
+/**
+ * gst_context_copy:
+ * @context: The context to copy
+ *
+ * Copy the context using the context specific copy function.
+ *
+ * Returns: (transfer full): the new context
+ */
+#ifdef _FOOL_GTK_DOC_
+G_INLINE_FUNC GstContext * gst_context_copy (const GstContext * context);
+#endif
+
+static inline GstContext *
+gst_context_copy (const GstContext * context)
+{
+  return GST_CONTEXT_CAST (gst_mini_object_copy (GST_MINI_OBJECT_CONST_CAST (context)));
+}
+
+GstContext *   gst_context_new         (void);
+
+void           gst_context_update      (GstContext *context, GstEvent *event);
+GstEvent *     gst_context_get         (GstContext *context, GstEventType type);
+
+void           gst_context_clear       (GstContext *context);
+
+G_END_DECLS
+
+#endif /* __GST_CONTEXT_H__ */

gst/gstevent.h

@@ -80,7 +80,8 @@ typedef enum {
 #define FLAG(name) GST_EVENT_TYPE_##name
 
 
-#define GST_EVENT_STICKY_IDX(ev)  ((GST_EVENT_TYPE(ev) >> GST_EVENT_STICKY_SHIFT) & 0xf)
+#define GST_EVENT_STICKY_IDX_TYPE(type)  (((type) >> GST_EVENT_STICKY_SHIFT) & 0xf)
+#define GST_EVENT_STICKY_IDX(ev)         GST_EVENT_STICKY_IDX_TYPE(GST_EVENT_TYPE(ev))
 
 /**
  * GstEventType: