[tracker/wip/carlosg/resources-as-cursors: 3/18] libtracker-sparql: Add private TrackerResource iterator helper

[Carlos Garnacho <carlosg src gnome org>]

commit 2717dcb043c9a1f3c66bdf9925a92e687d1ae5e2
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Jul 2 19:31:18 2022 +0200

    libtracker-sparql: Add private TrackerResource iterator helper
    
    This is a simple heap struct to iterate through the properties and
    values defined in a TrackerResource without requiring memory allocations.
    This helper does not handle recursivity, if TrackerResource values are
    found, these should be iterated separately.

 src/libtracker-sparql/tracker-private.h  | 14 ++++++++++
 src/libtracker-sparql/tracker-resource.c | 47 ++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)
---
diff --git a/src/libtracker-sparql/tracker-private.h b/src/libtracker-sparql/tracker-private.h
index 0e309e48e..8e3027486 100644
--- a/src/libtracker-sparql/tracker-private.h
+++ b/src/libtracker-sparql/tracker-private.h
@@ -304,6 +304,14 @@ struct _TrackerNamespaceManager {
        GObject parent;
 };
 
+typedef struct {
+       GHashTableIter prop_iter;
+       TrackerResource *cur_resource;
+       const gchar *cur_prop;
+       GPtrArray *cur_values;
+       guint idx;
+} TrackerResourceIterator;
+
 gboolean
 tracker_sparql_connection_lookup_dbus_service (TrackerSparqlConnection  *connection,
                                                const gchar              *dbus_name,
@@ -316,4 +324,10 @@ GError * _translate_internal_error (GError *error);
 
 void tracker_namespace_manager_seal (TrackerNamespaceManager *namespaces);
 
+void tracker_resource_iterator_init (TrackerResourceIterator *iter,
+                                     TrackerResource         *resource);
+gboolean tracker_resource_iterator_next (TrackerResourceIterator  *iter,
+                                         const gchar             **property,
+                                         const GValue            **value);
+
 #endif /* __TRACKER_PRIVATE_H__ */
diff --git a/src/libtracker-sparql/tracker-resource.c b/src/libtracker-sparql/tracker-resource.c
index de509fc78..4022091d6 100644
--- a/src/libtracker-sparql/tracker-resource.c
+++ b/src/libtracker-sparql/tracker-resource.c
@@ -2016,3 +2016,50 @@ tracker_resource_get_property_overwrite (TrackerResource *resource,
 
        return g_hash_table_contains (priv->overwrite, property_uri);
 }
+
+void
+tracker_resource_iterator_init (TrackerResourceIterator *iter,
+                                TrackerResource         *resource)
+{
+       TrackerResourcePrivate *priv = GET_PRIVATE (resource);
+
+       bzero (iter, sizeof (TrackerResourceIterator));
+       g_hash_table_iter_init (&iter->prop_iter, priv->properties);
+}
+
+gboolean
+tracker_resource_iterator_next (TrackerResourceIterator  *iter,
+                                const gchar             **property,
+                                const GValue            **value)
+{
+       gpointer key, val;
+
+       if (iter->cur_values && iter->cur_prop) {
+               iter->idx++;
+
+               if (iter->idx < iter->cur_values->len) {
+                       *property = iter->cur_prop;
+                       *value = g_ptr_array_index (iter->cur_values, iter->idx);
+                       return TRUE;
+               } else {
+                       iter->cur_values = NULL;
+                       iter->cur_prop = NULL;
+               }
+       }
+
+       if (!g_hash_table_iter_next (&iter->prop_iter, &key, &val))
+               return FALSE;
+
+       if (G_VALUE_HOLDS (val, G_TYPE_PTR_ARRAY)) {
+               iter->cur_prop = key;
+               iter->cur_values = g_value_get_boxed (val);
+               iter->idx = 0;
+               *property = iter->cur_prop;
+               *value = g_ptr_array_index (iter->cur_values, iter->idx);
+               return TRUE;
+       }
+
+       *property = key;
+       *value = val;
+       return TRUE;
+}