GMappedFile: Add g_mapped_file_get_bytes()

This is yet another API that has a data/length/refcount combination
that one might often want to turn into a GBytes.

https://bugzilla.gnome.org/show_bug.cgi?id=677065

glib/gmappedfile.c

@@ -400,3 +400,25 @@ g_mapped_file_unref (GMappedFile *file)
   if (g_atomic_int_dec_and_test (&file->ref_count))
     g_mapped_file_destroy (file);
 }
+
+/**
+ * g_mapped_file_get_bytes:
+ * @file: a #GMappedFile
+ *
+ * Creates a new #GBytes which references the data mapped from @file.
+ * It is invalid to use this function if @file is mapped writable,
+ * because a #GBytes should be immutable.
+ *
+ * Returns: (transfer full): A newly allocated #GBytes referencing data from @file
+ * Since: 2.34
+ **/
+GBytes *
+g_mapped_file_get_bytes (GMappedFile  *file)
+{
+  g_return_if_fail (file != NULL);
+
+  return g_bytes_new_with_free_func (file->contents,
+				     file->length,
+				     (GDestroyNotify) g_mapped_file_unref,
+				     g_mapped_file_ref (file));
+}

glib/gmappedfile.h

@@ -41,6 +41,8 @@ GMappedFile *g_mapped_file_new_from_fd  (gint          fd,
 					 GError      **error) G_GNUC_MALLOC;
 gsize        g_mapped_file_get_length   (GMappedFile  *file);
 gchar       *g_mapped_file_get_contents (GMappedFile  *file);
+GLIB_AVAILABLE_IN_2_34
+GBytes *     g_mapped_file_get_bytes    (GMappedFile  *file);
 GMappedFile *g_mapped_file_ref          (GMappedFile  *file);
 void         g_mapped_file_unref        (GMappedFile  *file);
 

glib/tests/mappedfile.c

@@ -147,6 +147,24 @@ test_writable_fd (void)
 
 }
 
+static void
+test_gbytes (void)
+{
+  GMappedFile *file;
+  GBytes *bytes;
+  GError *error;
+
+  error = NULL;
+  file = g_mapped_file_new (SRCDIR "/empty", FALSE, &error);
+  g_assert_no_error (error);
+
+  bytes = g_mapped_file_get_bytes (file);
+  g_mapped_file_unref (file);
+
+  g_assert_cmpint (g_bytes_get_size (bytes), ==, 0);
+  g_bytes_unref (bytes);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -158,6 +176,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/mappedfile/nonexisting", test_nonexisting);
   g_test_add_func ("/mappedfile/writable", test_writable);
   g_test_add_func ("/mappedfile/writable_fd", test_writable_fd);
+  g_test_add_func ("/mappedfile/gbytes", test_gbytes);
 
   return g_test_run ();
 }