gutf8: Add a g_utf8_validate_len() function

This is a variant of g_utf8_validate() which requires the length to be
specified, thereby allowing string lengths up to G_MAXSIZE rather than
just G_MAXSSIZE.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

glib/gunicodeprivate.h

@@ -20,6 +20,7 @@
 #define __G_UNICODE_PRIVATE_H__
 
 #include "gtypes.h"
+#include "gunicode.h"
 
 G_BEGIN_DECLS
 
@@ -27,6 +28,10 @@ gunichar *_g_utf8_normalize_wc (const gchar    *str,
                                 gssize          max_len,
 				GNormalizeMode  mode);
 
+gboolean _g_utf8_validate_len (const gchar  *str,
+                               gsize         max_len,
+                               const gchar **end);
+
 G_END_DECLS
 
 #endif /* __G_UNICODE_PRIVATE_H__ */

glib/gutf8.c

@@ -39,6 +39,7 @@
 #include "gtypes.h"
 #include "gthread.h"
 #include "glibintl.h"
+#include "gunicodeprivate.h"
 
 #define UTF8_COMPUTE(Char, Mask, Len)					      \
   if (Char < 128)							      \
@@ -1669,16 +1670,48 @@ g_utf8_validate (const char   *str,
 {
   const gchar *p;
 
-  if (max_len < 0)
-    p = fast_validate (str);
-  else
-    p = fast_validate_len (str, max_len);
+  if (max_len >= 0)
+    return _g_utf8_validate_len (str, max_len, end);
+
+  p = fast_validate (str);
 
   if (end)
     *end = p;
 
-  if ((max_len >= 0 && p != str + max_len) ||
-      (max_len < 0 && *p != '\0'))
+  if (*p != '\0')
+    return FALSE;
+  else
+    return TRUE;
+}
+
+/*
+ * _g_utf8_validate_len:
+ * @str: (array length=max_len) (element-type guint8): a pointer to character data
+ * @max_len: max bytes to validate
+ * @end: (out) (optional) (transfer none): return location for end of valid data
+ *
+ * Validates UTF-8 encoded text.
+ *
+ * As with g_utf8_validate(), but @max_len must be set, and hence this function
+ * will always return %FALSE if any of the bytes of @str are nul.
+ *
+ * Returns: %TRUE if the text was valid UTF-8
+ * Since: 2.60 (backported to 2.58)
+ */
+gboolean
+_g_utf8_validate_len (const char   *str,
+                      gsize         max_len,
+                      const gchar **end)
+
+{
+  const gchar *p;
+
+  p = fast_validate_len (str, max_len);
+
+  if (end)
+    *end = p;
+
+  if (p != str + max_len)
     return FALSE;
   else
     return TRUE;