gstring: add g_string_new_take

Adds a GString constructor that takes over ownership of an existing,
dynamically allocated, string.

docs/reference/glib/glib-sections.txt.in

@@ -2625,6 +2625,7 @@ g_str_hash
 <FILE>strings</FILE>
 GString
 g_string_new
+g_string_new_take
 g_string_new_len
 g_string_sized_new
 g_string_assign

glib/gstring.c

@@ -155,6 +155,39 @@ g_string_new (const gchar *init)
   return string;
 }
 
+/**
+ * g_string_new_take: (constructor)
+ * @init: (nullable) (transfer full): initial text used as the string.
+ *     Ownership of the string is transferred to the #GString.
+ *     Passing %NULL creates an empty string.
+ *
+ * Creates a new #GString, initialized with the given string.
+ *
+ * After this call, @init belongs to the #GString and may no longer be
+ * modified by the caller. The memory of @data has to be dynamically
+ * allocated and will eventually be freed with g_free().
+ *
+ * Returns: (transfer full): the new #GString
+ */
+GString *
+g_string_new_take (gchar *init)
+{
+  GString *string;
+
+  if (init == NULL)
+    {
+      return g_string_new (NULL);
+    }
+
+  string = g_slice_new (GString);
+
+  string->str = init;
+  string->len = strlen (string->str);
+  string->allocated_len = string->len + 1;
+
+  return string;
+}
+
 /**
  * g_string_new_len: (constructor)
  * @init: initial contents of the string

glib/gstring.h

@@ -51,6 +51,8 @@ struct _GString
 
 GLIB_AVAILABLE_IN_ALL
 GString*     g_string_new               (const gchar     *init);
+GLIB_AVAILABLE_IN_2_78
+GString*     g_string_new_take          (gchar           *init);
 GLIB_AVAILABLE_IN_ALL
 GString*     g_string_new_len           (const gchar     *init,
                                          gssize           len);

glib/tests/string.c

@@ -709,6 +709,40 @@ test_string_steal (void)
   g_free (str);
 }
 
+static void
+test_string_new_take (void)
+{
+  const char *test_str_const = "test_test";
+  const char *replaced_str_const = "test__test";
+  char *test_str = malloc (10 * sizeof (*test_str_const));
+  GString *string;
+
+  strcpy (test_str, test_str_const);
+  g_assert_cmpstr (test_str, ==, test_str_const);
+
+  string = g_string_new_take (g_steal_pointer (&test_str));
+  g_assert_null (test_str);
+  g_assert_nonnull (string);
+
+  g_string_replace (string, "_", "__", 0);
+  g_assert_cmpstr (string->str, ==, replaced_str_const);
+
+  test_str = g_string_free_and_steal (g_steal_pointer (&string));
+  g_assert_cmpstr (test_str, ==, replaced_str_const);
+
+  g_free (test_str);
+}
+
+static void
+test_string_new_take_null (void)
+{
+  GString *string = g_string_new_take (NULL);
+
+  g_assert_cmpstr (string->str, ==, "");
+
+  g_string_free (g_steal_pointer (&string), TRUE);
+}
+
 int
 main (int   argc,
       char *argv[])
@@ -736,6 +770,8 @@ main (int   argc,
   g_test_add_func ("/string/test-string-to-bytes", test_string_to_bytes);
   g_test_add_func ("/string/test-string-replace", test_string_replace);
   g_test_add_func ("/string/test-string-steal", test_string_steal);
+  g_test_add_func ("/string/test-string-new-take", test_string_new_take);
+  g_test_add_func ("/string/test-string-new-take/null", test_string_new_take_null);
 
   return g_test_run();
 }