Optimize g_irepository_find_by_gtype

When g_irepository_find_by_gtype() doesn't succeed on a simple prefix
match (the current 'fastpass' mechanism), it ends up taking a
considerable amount of CPU time, traversing the contents of all typelibs.

I imagine that the reasons to have the exhaustive search fallback are
not as strong as they used to be. For example, the case mentioned
(Clutter including Cogl) no longer seems to be true.

Also, typelibs (as generated by g-ir-scanner) now provide
comma-separated C prefix info for cases when the typelib includes
introspection info for multiple prefixes. For example, the Sugar typelib
has a c_prefix string of Sugar,EggSM,Gsm,Acme. So I imagine there are
not many remaining justified cases where the exhaustive search is needed.

With that in mind, I found two ways to optimize this function:

1. Support comma-separated C prefixes

2. Don't bother with an exhaustive search if we did find a typelib
   claiming support for the prefix. For example, if we're looking for
   GdkDeviceManagerXI2 (currently non-introspectable) and we already found
   typelib files providing the 'Gdk' prefix that didn't offer this, lets
   not bother with the exhaustive search, we aren't going to find anything.

1 files changed, 42 insertions, 42 deletions

diff --git a/girepository/gitypelib.c b/girepository/gitypelib.c
index 76a55de8..2512e524 100644
--- a/girepository/gitypelib.c
+++ b/girepository/gitypelib.c
@@ -198,55 +198,17 @@ g_typelib_get_dir_entry_by_name (GITypelib *typelib,
 }
 
 DirEntry *
-g_typelib_get_dir_entry_by_gtype (GITypelib *typelib,
-				  gboolean   fastpass,
-				  GType      gtype)
+g_typelib_get_dir_entry_by_gtype_name (GITypelib *typelib,
+				       const gchar *gtype_name)
 {
   Header *header = (Header *)typelib->data;
-  guint n_entries = header->n_local_entries;
-  const char *gtype_name = g_type_name (gtype);
-  DirEntry *entry;
   guint i;
-  const char *c_prefix;
 
-  /* There is a corner case regarding GdkRectangle.  GdkRectangle is a
-     boxed type, but it is just an alias to boxed struct
-     CairoRectangleInt.  Scanner automatically converts all references
-     to GdkRectangle to CairoRectangleInt, so GdkRectangle does not
-     appear in the typelibs at all, although user code might query it.
-     So if we get such query, we also change it to lookup of
-     CairoRectangleInt.
-     https://bugzilla.gnome.org/show_bug.cgi?id=655423 */
-  if (!fastpass && !strcmp (gtype_name, "GdkRectangle"))
-    gtype_name = "CairoRectangleInt";
-
-  /* Inside each typelib, we include the "C prefix" which acts as
-   * a namespace mechanism.  For GtkTreeView, the C prefix is Gtk.
-   * Given the assumption that GTypes for a library also use the
-   * C prefix, we know we can skip examining a typelib if our
-   * target type does not have this typelib's C prefix.
-   *
-   * However, not every class library necessarily conforms to this,
-   * e.g. Clutter has Cogl inside it.  So, we split this into two
-   * passes.  First we try a lookup, skipping things which don't
-   * have the prefix.  If that fails then we try a global lookup,
-   * ignoring the prefix.
-   *
-   * See http://bugzilla.gnome.org/show_bug.cgi?id=564016
-   */
-  c_prefix = g_typelib_get_string (typelib, header->c_prefix);
-  if (fastpass && c_prefix != NULL)
-    {
-      if (g_ascii_strncasecmp (c_prefix, gtype_name, strlen (c_prefix)) != 0)
-	return NULL;
-    }
-
-  for (i = 1; i <= n_entries; i++)
+  for (i = 1; i <= header->n_local_entries; i++)
     {
       RegisteredTypeBlob *blob;
       const char *type;
-
-      entry = g_typelib_get_dir_entry (typelib, i);
+      DirEntry *entry = g_typelib_get_dir_entry (typelib, i);
       if (!BLOB_IS_REGISTERED_TYPE (entry))
 	continue;
 
@@ -261,6 +223,44 @@ g_typelib_get_dir_entry_by_gtype (GITypelib *typelib,
   return NULL;
 }
 
+gboolean
+g_typelib_matches_gtype_name_prefix (GITypelib *typelib,
+				     const gchar *gtype_name)
+{
+  Header *header = (Header *)typelib->data;
+  const char *c_prefix;
+  gchar **prefixes;
+  gchar **prefix;
+  gboolean ret = FALSE;
+
+  c_prefix = g_typelib_get_string (typelib, header->c_prefix);
+  if (c_prefix == NULL)
+    return FALSE;
+
+  /* c_prefix is a comma separated string of supported prefixes
+   * in the typelib.
+   * We match the specified gtype_name if the gtype_name starts
+   * with the prefix, and is followed by a capital letter.
+   * For example, a typelib offering the 'Gdk' prefix does match
+   * GdkX11Cursor, however a typelib offering the 'G' prefix does not.
+   */
+  prefixes = g_strsplit (c_prefix, ",", 0);
+  for (prefix = prefixes; *prefix; prefix++)
+    {
+      size_t len = strlen (*prefix);
+      if (strncmp (*prefix, gtype_name, len))
+        continue;
+
+      if (strlen (gtype_name) > len && g_ascii_isupper (gtype_name[len]))
+        {
+          ret = TRUE;
+          break;
+        }
+    }
+  g_strfreev(prefixes);
+  return ret;
+}
+
 DirEntry *
 g_typelib_get_dir_entry_by_error_domain (GITypelib *typelib,
 					 GQuark     error_domain)