[tracker/wip/carlosg/serialize-api: 19/26] libtracker-sparql: Implement serialization on direct statements

[Carlos Garnacho <carlosg src gnome org>]

commit a9ab0b1fc63373f25713d7eba0890de270e31475
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Nov 27 14:08:10 2021 +0100

    libtracker-sparql: Implement serialization on direct statements

 .../direct/tracker-direct-statement.c              | 111 +++++++++++++++++++++
 1 file changed, 111 insertions(+)
---
diff --git a/src/libtracker-sparql/direct/tracker-direct-statement.c 
b/src/libtracker-sparql/direct/tracker-direct-statement.c
index ee6b54d7c..d232d064b 100644
--- a/src/libtracker-sparql/direct/tracker-direct-statement.c
+++ b/src/libtracker-sparql/direct/tracker-direct-statement.c
@@ -21,6 +21,7 @@
 #include "tracker-direct-statement.h"
 #include "tracker-data.h"
 #include "tracker-private.h"
+#include <libtracker-sparql/tracker-serializer.h>
 
 typedef struct _TrackerDirectStatementPrivate TrackerDirectStatementPrivate;
 
@@ -30,6 +31,12 @@ struct _TrackerDirectStatementPrivate
        GHashTable *values;
 };
 
+typedef struct
+{
+       GHashTable *values;
+       TrackerRdfFormat format;
+} RdfSerializationData;
+
 G_DEFINE_TYPE_WITH_PRIVATE (TrackerDirectStatement,
                             tracker_direct_statement,
                             TRACKER_TYPE_SPARQL_STATEMENT)
@@ -192,6 +199,71 @@ execute_in_thread (GTask        *task,
        g_object_unref (task);
 }
 
+static void
+rdf_serialization_data_free (RdfSerializationData *data)
+{
+       g_hash_table_unref (data->values);
+       g_free (data);
+}
+
+static TrackerSerializerFormat
+convert_format (TrackerRdfFormat format)
+{
+       switch (format) {
+       case TRACKER_RDF_FORMAT_TURTLE:
+               return TRACKER_SERIALIZER_FORMAT_TTL;
+       case TRACKER_RDF_FORMAT_TRIG:
+               return TRACKER_SERIALIZER_FORMAT_TRIG;
+       default:
+               g_assert_not_reached ();
+       }
+}
+
+static void
+serialize_in_thread (GTask        *task,
+                     gpointer      object,
+                     gpointer      task_data,
+                     GCancellable *cancellable)
+{
+       TrackerSparqlConnection *conn;
+       TrackerDirectStatementPrivate *priv;
+       TrackerSparqlCursor *cursor = NULL;
+       RdfSerializationData *data = task_data;
+       GInputStream *istream = NULL;
+       GError *error = NULL;
+
+       if (g_task_return_error_if_cancelled (task))
+               return;
+
+       priv = tracker_direct_statement_get_instance_private (object);
+       if (!tracker_sparql_is_serializable (priv->sparql)) {
+               g_set_error (&error,
+                            TRACKER_SPARQL_ERROR,
+                            TRACKER_SPARQL_ERROR_PARSE,
+                            "Query is not DESCRIBE or CONSTRUCT");
+               goto out;
+       }
+
+       cursor = tracker_sparql_execute_cursor (priv->sparql, data->values, &error);
+       if (!cursor)
+               goto out;
+
+       conn = tracker_sparql_statement_get_connection (object);
+       tracker_direct_connection_update_timestamp (TRACKER_DIRECT_CONNECTION (conn));
+       tracker_sparql_cursor_set_connection (cursor, conn);
+       istream = tracker_serializer_new (cursor, convert_format (data->format));
+
+ out:
+       g_clear_object (&cursor);
+
+       if (istream)
+               g_task_return_pointer (task, istream, g_object_unref);
+       else
+               g_task_return_error (task, error);
+
+       g_object_unref (task);
+}
+
 static void
 free_gvalue (gpointer data)
 {
@@ -268,6 +340,43 @@ tracker_direct_statement_execute_finish (TrackerSparqlStatement  *stmt,
        return cursor;
 }
 
+static void
+tracker_direct_statement_serialize_async (TrackerSparqlStatement *stmt,
+                                          TrackerRdfFormat        format,
+                                          GCancellable           *cancellable,
+                                          GAsyncReadyCallback     callback,
+                                          gpointer                user_data)
+{
+       TrackerDirectStatementPrivate *priv;
+       RdfSerializationData *data;
+       GTask *task;
+
+       priv = tracker_direct_statement_get_instance_private (TRACKER_DIRECT_STATEMENT (stmt));
+
+       data = g_new0 (RdfSerializationData, 1);
+       data->values = copy_values_deep (priv->values);
+       data->format = format;
+
+       task = g_task_new (stmt, cancellable, callback, user_data);
+       g_task_set_task_data (task, data, (GDestroyNotify) rdf_serialization_data_free);
+       g_task_run_in_thread (task, serialize_in_thread);
+}
+
+static GInputStream *
+tracker_direct_statement_serialize_finish (TrackerSparqlStatement  *stmt,
+                                           GAsyncResult            *res,
+                                           GError                 **error)
+{
+       GError *inner_error = NULL;
+       GInputStream *istream;
+
+       istream = g_task_propagate_pointer (G_TASK (res), &inner_error);
+       if (inner_error)
+               g_propagate_error (error, _translate_internal_error (inner_error));
+
+       return istream;
+}
+
 static void
 tracker_direct_statement_class_init (TrackerDirectStatementClass *klass)
 {
@@ -286,6 +395,8 @@ tracker_direct_statement_class_init (TrackerDirectStatementClass *klass)
        stmt_class->execute = tracker_direct_statement_execute;
        stmt_class->execute_async = tracker_direct_statement_execute_async;
        stmt_class->execute_finish = tracker_direct_statement_execute_finish;
+       stmt_class->serialize_async = tracker_direct_statement_serialize_async;
+       stmt_class->serialize_finish = tracker_direct_statement_serialize_finish;
 }
 
 static void