Subject: Re: bug#42998: 27.1; gnutls-symmetric-encrypt slow when providing cipher as symbol

From: Lars Ingebrigtsen <[email-masked]>
Date: Mon, 24 Aug 2020 15:01:01 +0200

Vasilij Schneidermann <[email-masked]> writes:

> I'd consider either to
> document this behavior or making the mapping more efficient, for example
> by caching the cipher list instead of recomputing it over and over
> again.

The following fixes the problem, but I'm not quite sure whether it's
correct...  Is initialising a Lisp_Object to NULL something that's
allowed over all platforms?  I can't initialise it to the more natural
Qnil, since that's not a constant, C-wise.

diff --git a/src/gnutls.c b/src/gnutls.c
index 416fb15470..75bc7d970f 100644
--- a/src/gnutls.c
+++ b/src/gnutls.c
@@ -2303,6 +2303,8 @@ gnutls_symmetric (bool encrypting, Lisp_Object cipher,
                   Lisp_Object key, Lisp_Object iv,
                   Lisp_Object input, Lisp_Object aead_auth)
 {
+  static Lisp_Object cipher_cache = NULL;
+
   if (BUFFERP (key) || STRINGP (key))
     key = list1 (key);
 
@@ -2329,7 +2331,12 @@ gnutls_symmetric (bool encrypting, Lisp_Object cipher,
 
   if (SYMBOLP (cipher))
     {
-      info = Fassq (cipher, Fgnutls_ciphers ());
+      if (! cipher_cache)
+	{
+	  cipher_cache = Fgnutls_ciphers ();
+	  staticpro (&cipher_cache);
+	}
+      info = Fassq (cipher, cipher_cache);
       if (!CONSP (info))
 	xsignal2 (Qerror,
 		  build_string ("GnuTLS cipher is invalid or not found"),

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no