Better seed support for (random).

* doc/lispref/numbers.texi (Random Numbers): Document new behavior of
the calls (random) and (random STRING).
* etc/NEWS: Document new behavior of (random), (random "string").
* lisp/play/5x5.el, lisp/play/animate.el, lisp/play/cookie1.el:
* lisp/play/dissociate.el, lisp/play/doctor.el, lisp/play/dunnet.el:
* lisp/play/gomoku.el, lisp/play/landmark.el, lisp/play/mpuz.el:
* lisp/play/tetris.el, lisp/play/zone.el:
* lisp/calc/calc-comb.el (math-init-random-base):
* lisp/play/blackbox.el (bb-init-board):
* lisp/play/life.el (life):
* lisp/server.el (server-use-tcp):
* lisp/type-break.el (type-break):
Remove unnecessary call to (random t).
* lisp/net/sasl.el (sasl-unique-id-function):
Change (random t) to (random), now that the latter is more random.
* lisp/play/life.el (life-initialized): Remove no-longer-needed var.
* lisp/gnus/gnus-sync.el (gnus-sync-lesync-setup):
* lisp/gnus/message.el (message-canlock-generate, message-unique-id):
Change (random t) to (random), now that the latter is more random.
* lisp/org/org-id.el (org-id-uuid):
Change (random t) to (random), now that the latter is more random.
* src/emacs.c (main): Call init_random.
* src/fns.c (Frandom): Set the seed from a string argument, if given.
Remove long-obsolete Gentzel cruft.
* src/lisp.h, src/sysdep.c (seed_random): Now takes address and size, not long.
(init_random): New function.

5 files changed, 39 insertions, 26 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 4db48bbb969..ad96c948466 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2012-09-01  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Better seed support for (random).
+        * emacs.c (main): Call init_random.
+        * fns.c (Frandom): Set the seed from a string argument, if given.
+        Remove long-obsolete Gentzel cruft.
+        * lisp.h, sysdep.c (seed_random): Now takes address and size, not long.
+        (init_random): New function.
+
 2012-08-31  Dmitry Antipov  <dmantipov@yandex.ru>
 
         Remove mark_ttys function and fix tty_display_info initialization.
diff --git a/src/emacs.c b/src/emacs.c
index 7ff5c43dbea..842546461b6 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -1281,6 +1281,7 @@ Using an Emacs configured with --with-x-toolkit=lucid does not have this problem
   init_data ();
   init_atimer ();
   running_asynch_code = 0;
+  init_random ();
 
   no_loadup
     = argmatch (argv, argc, "-nl", "--no-loadup", 6, NULL, &skip_args);
diff --git a/src/fns.c b/src/fns.c
index f6acdcada3f..2dee8515799 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -74,32 +74,16 @@ Other values of LIMIT are ignored.  */)
   (Lisp_Object limit)
 {
   EMACS_INT val;
-  Lisp_Object lispy_val;
 
   if (EQ (limit, Qt))
-    {
-      EMACS_TIME t = current_emacs_time ();
-      seed_random (getpid () ^ EMACS_SECS (t) ^ EMACS_NSECS (t));
-    }
+    init_random ();
+  else if (STRINGP (limit))
+    seed_random (SSDATA (limit), SBYTES (limit));
 
+  val = get_random ();
   if (NATNUMP (limit) && XFASTINT (limit) != 0)
-    {
-      /* Try to take our random number from the higher bits of VAL,
-         not the lower, since (says Gentzel) the low bits of `random'
-         are less random than the higher ones.  We do this by using the
-         quotient rather than the remainder.  At the high end of the RNG
-         it's possible to get a quotient larger than n; discarding
-         these values eliminates the bias that would otherwise appear
-         when using a large n.  */
-      EMACS_INT denominator = (INTMASK + 1) / XFASTINT (limit);
-      do
-        val = get_random () / denominator;
-      while (val >= XFASTINT (limit));
-    }
-  else
-    val = get_random ();
-  XSETINT (lispy_val, val);
-  return lispy_val;
+    val %= XFASTINT (limit);
+  return make_number (val);
 }
 
 /* Heuristic on how many iterations of a tight loop can be safely done
diff --git a/src/lisp.h b/src/lisp.h
index 80c49703f52..2815a2ae325 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3405,7 +3405,8 @@ extern void child_setup_tty (int);
 extern void setup_pty (int);
 extern int set_window_size (int, int, int);
 extern EMACS_INT get_random (void);
-extern void seed_random (long);
+extern void seed_random (void *, ptrdiff_t);
+extern void init_random (void);
 extern int emacs_open (const char *, int, int);
 extern int emacs_close (int);
 extern ptrdiff_t emacs_read (int, char *, ptrdiff_t);
diff --git a/src/sysdep.c b/src/sysdep.c
index 183ee005227..edd54de84d4 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1765,19 +1765,37 @@ init_signals (void)
 #endif /* !RAND_BITS */
 
 void
-seed_random (long int arg)
+seed_random (void *seed, ptrdiff_t seed_size)
 {
+#if defined HAVE_RANDOM || ! defined HAV_LRAND48
+  unsigned int arg = 0;
+#else
+  long int arg = 0;
+#endif
+  unsigned char *argp = (unsigned char *) &arg;
+  unsigned char *seedp = seed;
+  ptrdiff_t i;
+  for (i = 0; i < seed_size; i++)
+    argp[i % sizeof arg] ^= seedp[i];
 #ifdef HAVE_RANDOM
-  srandom ((unsigned int)arg);
+  srandom (arg);
 #else
 # ifdef HAVE_LRAND48
   srand48 (arg);
 # else
-  srand ((unsigned int)arg);
+  srand (arg);
 # endif
 #endif
 }
 
+void
+init_random (void)
+{
+  EMACS_TIME t = current_emacs_time ();
+  uintmax_t v = getpid () ^ EMACS_SECS (t) ^ EMACS_NSECS (t);
+  seed_random (&v, sizeof v);
+}
+
 /*
  * Return a nonnegative random integer out of whatever we've got.
  * It contains enough bits to make a random (signed) Emacs fixnum.