tracerrecord: add a log record class

We use this class to register tracer log entry metadata and build a log
template. With the log template we can serialize log data very efficiently.
This also simplifies the logging code, since that is now a simple varargs
function that is not exposing the implementation details.

Add docs for the new class and basic tests.

Remove the previous log handler.

Fixes #760267

1 files changed, 251 insertions, 0 deletions

diff --git a/gst/gsttracerrecord.c b/gst/gsttracerrecord.c
new file mode 100644
index 0000000000..060aead6d7
--- /dev/null
+++ b/gst/gsttracerrecord.c
@@ -0,0 +1,251 @@
+/* GStreamer
+ * Copyright (C) 2016 Stefan Sauer <ensonic@users.sf.net>
+ *
+ * gsttracerrecord.c: tracer log record class
+ *
+ * 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., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+/**
+ * SECTION:gsttracerrecord
+ * @short_description: Trace log entry class
+ *
+ * Tracing modules will create instances of this class to announce the data they
+ * will log and create a log formatter.
+ *
+ * Since: 1.8
+ */
+
+#define GST_USE_UNSTABLE_API
+
+#include "gst_private.h"
+#include "gstinfo.h"
+#include "gststructure.h"
+#include "gsttracerrecord.h"
+#include "gstvalue.h"
+
+GST_DEBUG_CATEGORY_EXTERN (tracer_debug);
+#define GST_CAT_DEFAULT tracer_debug
+
+
+enum
+{
+  PROP_0,
+  PROP_SPEC,
+  PROP_LAST
+};
+
+static GParamSpec *properties[PROP_LAST];
+
+struct _GstTracerRecord
+{
+  GstObject parent;
+
+  GstStructure *spec;
+  gchar *format;
+};
+
+struct _GstTracerRecordClass
+{
+  GstObjectClass parent_class;
+};
+
+#define gst_tracer_record_parent_class parent_class
+G_DEFINE_TYPE (GstTracerRecord, gst_tracer_record, GST_TYPE_OBJECT);
+
+static gboolean
+build_field_template (GQuark field_id, const GValue * value, gpointer user_data)
+{
+  GString *s = (GString *) user_data;
+  const GstStructure *sub;
+  GValue template_value = { 0, };
+  GType type;
+  gboolean res;
+
+  g_return_val_if_fail (G_VALUE_TYPE (value) == GST_TYPE_STRUCTURE, FALSE);
+
+  sub = gst_value_get_structure (value);
+  type = g_value_get_gtype (gst_structure_get_value (sub, "type"));
+  g_value_init (&template_value, type);
+
+  res = priv__gst_structure_append_template_to_gstring (field_id,
+      &template_value, s);
+  g_value_unset (&template_value);
+  return res;
+}
+
+static void
+gst_tracer_record_build_format (GstTracerRecord * self)
+{
+  GstStructure *structure = self->spec;
+  GString *s;
+  gchar *name = (gchar *) g_quark_to_string (structure->name);
+  gchar *p;
+
+  g_return_if_fail (g_str_has_suffix (name, ".class"));
+
+  GST_TRACE ("%" GST_PTR_FORMAT, structure);
+
+  /* cut off '.class' suffix */
+  name = g_strdup (name);
+  p = strrchr (name, '.');
+  *p = '\0';
+
+  s = g_string_sized_new (STRUCTURE_ESTIMATED_STRING_LEN (structure));
+  g_string_append (s, name);
+  gst_structure_foreach (structure, build_field_template, s);
+  g_string_append_c (s, ';');
+
+  self->format = g_string_free (s, FALSE);
+  GST_INFO ("new format string: %s", self->format);
+  g_free (name);
+}
+
+static void
+gst_tracer_record_dispose (GObject * object)
+{
+  GstTracerRecord *self = GST_TRACER_RECORD (object);
+
+  gst_structure_free (self->spec);
+  g_free (self->format);
+}
+
+static void
+gst_tracer_record_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstTracerRecord *self = GST_TRACER_RECORD_CAST (object);
+
+  switch (prop_id) {
+    case PROP_SPEC:
+      self->spec = g_value_get_boxed (value);
+      gst_tracer_record_build_format (self);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_tracer_record_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstTracerRecord *self = GST_TRACER_RECORD_CAST (object);
+
+  switch (prop_id) {
+    case PROP_SPEC:
+      // TODO(ensonic): copy?
+      g_value_set_boxed (value, self->spec);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_tracer_record_class_init (GstTracerRecordClass * klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->set_property = gst_tracer_record_set_property;
+  gobject_class->get_property = gst_tracer_record_get_property;
+  gobject_class->dispose = gst_tracer_record_dispose;
+
+  properties[PROP_SPEC] =
+      g_param_spec_boxed ("spec", "Spec", "Log record specification",
+      GST_TYPE_STRUCTURE,
+      G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (gobject_class, PROP_LAST, properties);
+}
+
+static void
+gst_tracer_record_init (GstTracerRecord * self)
+{
+}
+
+/**
+ * gst_tracer_record_new:
+ * @spec: the record specification
+ *
+ * Create a new tracer record. The record instance can be used to efficiently
+ * log entries using gst_tracer_record_log().
+ *
+ * The name of the @spec #GstStructure must end on '.class'. This name without
+ * the suffix will be used for the log records. The @spec must have a field for
+ * each value that gets logged where the field name is the value name. The field
+ * must be a nested structure describing the value. The sub structure must
+ * contain a field called 'type' of %G_TYPE_GTYPE that contains the GType of the
+ * value.
+ *
+ * The way to deal with optional values is to log an additional boolean before
+ * the optional field, that if %TRUE signals that the optional field is valid
+ * and %FALSE signals that the optional field should be ignored. One must still
+ * log a placeholder value for the optional field though. Please also note, that
+ * pointer type values must not be NULL - the underlying serialisation can not
+ * handle that right now.
+ *
+ * <note><para>
+ *   Please note that this is still under discussion and subject to change.
+ * </para></note>
+ *
+ * Returns: a new #GstTracerRecord
+ */
+GstTracerRecord *
+gst_tracer_record_new (GstStructure * spec)
+{
+  return g_object_new (GST_TYPE_TRACER_RECORD, "spec", spec, NULL);
+}
+
+/**
+ * gst_tracer_record_log:
+ * @self: the tracer-record
+ * @...: the args as described in the spec-
+ *
+ * Serialzes the trace event into the log.
+ *
+ * Right now this is using the gstreamer debug log with the level TRACE (7) and
+ * the category "GST_TRACER".
+ * <note><para>
+ *   Please note that this is still under discussion and subject to change.
+ * </para></note>
+ */
+void
+gst_tracer_record_log (GstTracerRecord * self, ...)
+{
+  va_list var_args;
+
+  /*
+   * does it make sense to use the {file, line, func} from the tracer hook?
+   * a)
+   * - we'd need to pass them in the macros to gst_tracer_dispatch()
+   * - and each tracer needs to grab them from the va_list and pass them here
+   * b)
+   * - we create a context in dispatch, pass that to the tracer
+   * - and the tracer will pass that here
+   * ideally we also use *our* ts instead of the one that
+   * gst_debug_log_default() will pick
+   */
+
+  va_start (var_args, self);
+  if (G_LIKELY (GST_LEVEL_TRACE <= _gst_debug_min)) {
+    gst_debug_log_valist (GST_CAT_DEFAULT, GST_LEVEL_TRACE, "", "", 0, NULL,
+        self->format, var_args);
+  }
+  va_end (var_args);
+}