Add native UUID generator.

While not necessary, since we barely use UUID:s, it's still WAY faster,
and nice to not depend on the system providing `uuidgen'.

For comparison, number of UUID:s generated by different settups in 1
second:

   65.000 :: guile native
      700 :: guile shell-out
3.500.000 :: c native
  100.000 :: libuuid - guile bindings
  650.000 :: libuuid

Tests where run with either
    (call-with-time-limit
      1
      (lambda ()
	(let loop ()
	 (uuid)
	 (set! count (1+ count))
	 (loop)))
      (lambda _ (display count)))
or
    volatile unsigned long long count = 0;
    sigaction(SIGALARM, ...);
    alarm(1);
    for (;;) {
	uuid();
	count++;
    }

(let ((count 0))
  (call-with-time-limit
   1
   (lambda ()
     (let loop ()
       ((@ (hnh util) uuidgen))
       (set! count (1+ count))
       (loop)))
   (lambda _ (format #t "exec count = ~:d~%" count))))

1 files changed, 9 insertions, 2 deletions

diff --git a/doc/ref/guile/util.texi b/doc/ref/guile/util.texi
index 71e3f93a..2cf1070b 100644
--- a/doc/ref/guile/util.texi
+++ b/doc/ref/guile/util.texi
@@ -338,7 +338,14 @@ Similar to @var{let}, but sets environment variables for the code in
 body. Restores the old values once we leave.
 @end defmac
 
+@subsection UUID generation
 
-@defun uuidgen
-Generates a UUID.
+Provided by module @code{(hnh util uuid)}.
+
+@defun uuid-v4
+Generates a UUID-v4 string.
+@end defun
+
+@defun uuid
+Generates an implementation defined (but guaranteed valid) UUID.
 @end defun