Fixes for #101264 and #99372:

[platform/upstream/glib.git] / glib / grand.c

diff --git a/glib/grand.c b/glib/grand.c
index 36d53ff..ef28b82 100644 (file)
--- a/glib/grand.c
+++ b/glib/grand.c
@@ -22,7 +22,7 @@
  * code from this file in your own programs or libraries.
  * Further information on the Mersenne Twister can be found at
  * http://www.math.keio.ac.jp/~matumoto/emt.html
- * This code was adapted to glib by Sebastian Wilhelmi <wilhelmi@ira.uka.de>.
+ * This code was adapted to glib by Sebastian Wilhelmi.
  */
 
 /*
@@ -36,9 +36,14 @@
  * MT safe
  */
 
-#include <glib.h>
+#include "config.h"
+
 #include <math.h>
 #include <stdio.h>
+#include <string.h>
+
+#include "glib.h"
+#include "gthreadinit.h"
 
 G_LOCK_DEFINE_STATIC (global_random);
 static GRand* global_random = NULL;
@@ -88,7 +93,7 @@ get_random_version (void)
  * initialize some static data in a threadsafe way.
  */
 void 
-g_rand_init (void)
+_g_rand_thread_init (void)
 {
   (void)get_random_version ();
 }
@@ -281,34 +286,63 @@ g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
   g_return_val_if_fail (rand != NULL, begin);
   g_return_val_if_fail (end > begin, begin);
 
-  /* All tricks doing modulo calculations do not have a perfect
-   * distribution -> We must use the slower way through gdouble for
-   * maximal quality. */
-   
-  if (dist <= 0x10000L) /* 2^16 */
-    {
-      /* This method, which only calls g_rand_int once is only good
-       * for (end - begin) <= 2^16, because we only have 32 bits set
-       * from the one call to g_rand_int (). */
-
-      /* we are using (trans + trans * trans), because g_rand_int only
-       * covers [0..2^32-1] and thus g_rand_int * trans only covers
-       * [0..1-2^-32], but the biggest double < 1 is 1-2^-52. 
-       */
-
-      gdouble double_rand = g_rand_int (rand) * 
-       (G_RAND_DOUBLE_TRANSFORM +
-        G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
-      
-      random = (gint32) (double_rand * dist);
-    }
-  else
+  switch (get_random_version ())
     {
-      /* Now we use g_rand_double_range (), which will set 52 bits for
-         us, so that it is safe to round and still get a decent
-         distribution */
-       random = (gint32) g_rand_double_range (rand, 0, dist);
-    }
+    case 20:
+      if (dist <= 0x10000L) /* 2^16 */
+       {
+         /* This method, which only calls g_rand_int once is only good
+          * for (end - begin) <= 2^16, because we only have 32 bits set
+          * from the one call to g_rand_int (). */
+         
+         /* we are using (trans + trans * trans), because g_rand_int only
+          * covers [0..2^32-1] and thus g_rand_int * trans only covers
+          * [0..1-2^-32], but the biggest double < 1 is 1-2^-52. 
+          */
+         
+         gdouble double_rand = g_rand_int (rand) * 
+           (G_RAND_DOUBLE_TRANSFORM +
+            G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
+         
+         random = (gint32) (double_rand * dist);
+       }
+      else
+       {
+         /* Now we use g_rand_double_range (), which will set 52 bits for
+            us, so that it is safe to round and still get a decent
+            distribution */
+         random = (gint32) g_rand_double_range (rand, 0, dist);
+       }
+      break;
+    case 22:
+      if (dist == 0)
+       random = 0;
+      else 
+       {
+         /* maxvalue is set to the predecessor of the greatest
+          * multiple of dist less or equal 2^32. */
+         guint32 maxvalue;
+         if (dist <= 0x80000000u) /* 2^31 */
+           {
+             /* maxvalue = 2^32 - 1 - (2^32 % dist) */
+             guint32 leftover = (0x80000000u % dist) * 2;
+             if (leftover >= dist) leftover -= dist;
+             maxvalue = 0xffffffffu - leftover;
+           }
+         else
+           maxvalue = dist - 1;
+         
+         do
+           random = g_rand_int (rand);
+         while (random > maxvalue);
+         
+         random %= dist;
+       }
+      break;
+    default:
+      random = 0;              /* Quiet GCC */
+      g_assert_not_reached ();
+    }      
  
   return begin + random;
 }