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authorJonas Dreßler <verdre@v0yd.nl>2020-02-12 11:45:57 +0100
committerJonas Dreßler <verdre@v0yd.nl>2020-06-07 18:23:18 +0200
commitf1ad230857df4a9d34f2230ecff41fe03ec89800 (patch)
treed946a017fca6626f30230586865a0a33404aaaa9 /pango/pango-attributes.c
parent9774cb24ea7d049abdc0d9fd5da2e8e3170f1a05 (diff)
downloadpango-f1ad230857df4a9d34f2230ecff41fe03ec89800.tar.gz
Add API to compare PangoAttrLists
Add a new `pango_attr_list_equal` API that allows comparing the attributes included in two PangoAttrLists and returns TRUE if the lists contain the same attributes and apply to the same ranges. The function avoids any copying of attributes or lists and applies a minor optimization of skipping the equality check for attributes that were already found in both lists. Other possible optimizations that could be added if necessary would be storing the length of the attributes list in the PangoAttrList class to avoid the `g_slist_length` calls or reusing the `other_iter` pointer in case all attributes from 0 to n were already found.
Diffstat (limited to 'pango/pango-attributes.c')
-rw-r--r--pango/pango-attributes.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/pango/pango-attributes.c b/pango/pango-attributes.c
index 2d2dd2a2..03a45de4 100644
--- a/pango/pango-attributes.c
+++ b/pango/pango-attributes.c
@@ -1916,6 +1916,82 @@ pango_attr_list_get_attributes (PangoAttrList *list)
return g_slist_copy_deep (list->attributes, (GCopyFunc)pango_attribute_copy, NULL);
}
+/**
+ * pango_attr_list_equal:
+ * @list: a #PangoAttrList
+ * @other_list: the other #PangoAttrList
+ *
+ * Checks whether @list and @other_list contain the same attributes and
+ * whether those attributes apply to the same ranges. Beware that this
+ * will return wrong values if any list contains duplicates.
+ *
+ * Return value: %TRUE if the lists are equal, %FALSE if they aren't.
+ *
+ * Since: 1.46
+ */
+gboolean
+pango_attr_list_equal (PangoAttrList *list,
+ PangoAttrList *other_list)
+{
+ GSList *attrs, *other_attrs;
+ GSList *iter = NULL;
+ guint attrs_length = 0;
+ guint64 skip_bitmask = 0;
+
+ if (list == other_list)
+ return TRUE;
+
+ if (list == NULL || other_list == NULL)
+ return FALSE;
+
+ attrs = list->attributes;
+ other_attrs = other_list->attributes;
+
+ for (iter = attrs; iter != NULL; iter = iter->next)
+ {
+ PangoAttribute *attr = iter->data;
+ GSList *other_iter = NULL;
+ gboolean attr_equal = FALSE;
+ guint other_attr_index = 0;
+
+ attrs_length++;
+
+ for (other_iter = other_attrs;
+ other_iter != NULL;
+ other_iter = other_iter->next)
+ {
+ PangoAttribute *other_attr = other_iter->data;
+ guint64 other_attr_bitmask =
+ other_attr_index < 64 ? 1 << other_attr_index : 0;
+
+ if ((skip_bitmask & other_attr_bitmask) != 0)
+ {
+ other_attr_index++;
+ continue;
+ }
+
+ if (attr->start_index == other_attr->start_index &&
+ attr->end_index == other_attr->end_index &&
+ pango_attribute_equal (attr, other_attr))
+ {
+ skip_bitmask |= other_attr_bitmask;
+ attr_equal = TRUE;
+ break;
+ }
+
+ other_attr_index++;
+ }
+
+ if (!attr_equal)
+ return FALSE;
+ }
+
+ if (attrs_length != g_slist_length (other_attrs))
+ return FALSE;
+
+ return TRUE;
+}
+
G_DEFINE_BOXED_TYPE (PangoAttrIterator,
pango_attr_iterator,
pango_attr_iterator_copy,