From http://www.jwz.org/xscreensaver/xscreensaver-5.40.tar.gz

[xscreensaver] / utils / yarandom.h

diff --git a/utils/yarandom.h b/utils/yarandom.h
index 6563be7ed29ef2d41a090a9ed61caf0e5aa36edc..711aadd35a90ebaaa399edc11c9c3604b984fce9 100644 (file)
--- a/utils/yarandom.h
+++ b/utils/yarandom.h
@@ -1,4 +1,4 @@
-/* xscreensaver, Copyright (c) 1997 by Jamie Zawinski <jwz@netscape.com>
+/* xscreensaver, Copyright (c) 1997, 1998, 2003 by Jamie Zawinski <jwz@jwz.org>
  *
  * Permission to use, copy, modify, distribute, and sell this software and its
  * documentation for any purpose is hereby granted without fee, provided that
@@ -12,6 +12,14 @@
 #ifndef __YARANDOM_H__
 #define __YARANDOM_H__
 
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#ifdef HAVE_INTTYPES_H
+# include <inttypes.h>
+#endif
+
 #undef random
 #undef rand
 #undef drand48
@@ -19,34 +27,77 @@
 #undef srand
 #undef srand48
 #undef frand
+#undef RAND_MAX
 
 #ifdef VMS
 # include "vms-gtod.h"
 #endif
 
-#define random()   ya_random()
-#define srandom(i) ya_rand_init(0)
-
 extern unsigned int ya_random (void);
 extern void ya_rand_init (unsigned int);
 
+#define random()   ya_random()
+#define RAND_MAX   0xFFFFFFFF
+
+/*#define srandom(i) ya_rand_init(0)*/
+
+/* Define these away to keep people from using the wrong APIs in xscreensaver.
+ */
+#define rand          __ERROR_use_random_not_rand_in_xscreensaver__
+#define drand48       __ERROR_use_frand_not_drand48_in_xscreensaver__
+#define srandom       __ERROR_do_not_call_srandom_in_xscreensaver__
+#define srand         __ERROR_do_not_call_srand_in_xscreensaver__
+#define srand48       __ERROR_do_not_call_srand48_in_xscreensaver__
+#define ya_rand_init  __ERROR_do_not_call_ya_rand_init_in_xscreensaver__
+
 
 #if defined (__GNUC__) && (__GNUC__ >= 2)
  /* Implement frand using GCC's statement-expression extension. */
 
 # define frand(f)                                                      \
-  ({ double tmp = (((double) random()) /                               \
-                  (((double) ((unsigned int)~0)) / ((double) (f))));   \
+  __extension__                                                                \
+  ({ double tmp = ((((double) random()) * ((double) (f))) /            \
+                  ((double) ((unsigned int)~0)));                      \
      tmp < 0 ? (-tmp) : tmp; })
 
 #else /* not GCC2 - implement frand using a global variable.*/
 
 static double _frand_tmp_;
 # define frand(f)                                                      \
-  (_frand_tmp_ = (((double) random()) /                                \
-                 (((double) ((unsigned int)~0)) / ((double) (f)))),    \
+  (_frand_tmp_ = ((((double) random()) * ((double) (f))) /             \
+                 ((double) ((unsigned int)~0))),                       \
    _frand_tmp_ < 0 ? (-_frand_tmp_) : _frand_tmp_)
 
 #endif /* not GCC2 */
 
+/* Compatibility with the xlockmore RNG API
+   (note that the xlockmore hacks never expect negative numbers.)
+ */
+#define LRAND()         ((long) (random() & 0x7fffffff))
+
+/* The first NRAND(n) is much faster, when uint64_t is available to allow it.
+ * Especially on ARM and other processors without built-in division.
+ *
+ * n must be greater than zero.
+ *
+ * The division by RAND_MAX+1 should optimize down to a bit shift.
+ *
+ * Although the result here is never negative, this needs to return signed
+ * integers: A binary operator in C requires operands have the same type, and
+ * if one side is signed and the other is unsigned, but they're both the same
+ * size, then the signed operand is cast to unsigned, and the result is
+ * similarly unsigned. This can potentially cause problems when idioms like
+ * "NRAND(n) * RANDSIGN()" (where RANDSIGN() returns either -1 or 1) is used
+ * to get random numbers from the range (-n,n).
+ */
+#ifdef HAVE_INTTYPES_H
+# define NRAND(n)       ((int32_t) ((uint64_t) random() * (uint32_t) (n) / \
+                                    ((uint64_t) RAND_MAX + 1)))
+#else
+# define NRAND(n)       ((int) (LRAND() % (n)))
+#endif
+
+#define MAXRAND         (2147483648.0) /* unsigned 1<<31 as a float */
+#define SRAND(n)        /* already seeded by screenhack.c */
+
 #endif /* __YARANDOM_H__ */