From c8305fa82c94b442ea8a305e35715580bee49962 Mon Sep 17 00:00:00 2001
From: simon <simon@cda61777-01e9-0310-a592-d414129be87e>
Date: Thu, 14 Jul 2005 17:37:05 +0000
Subject: [PATCH] Introduce a `shuffle' utility function.

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@6090 cda61777-01e9-0310-a592-d414129be87e
---
 misc.c    | 16 ++++++++++++++++
 puzzles.h |  3 +++
 2 files changed, 19 insertions(+)

diff --git a/misc.c b/misc.c
index 025083d..17ec48c 100644
--- a/misc.c
+++ b/misc.c
@@ -196,4 +196,20 @@ void game_mkhighlight(frontend *fe, float *ret,
     }
 }
 
+void shuffle(void *array, int nelts, int eltsize, random_state *rs)
+{
+    char *tmp = smalloc(eltsize);
+    char *carray = (char *)array;
+    int i;
+
+    for (i = nelts; i-- > 1 ;) {
+        int j = random_upto(rs, i+1);
+        if (j != i) {
+            memcpy(tmp, carray + eltsize * i, eltsize);
+            memcpy(carray + eltsize * i, carray + eltsize * j, eltsize);
+            memcpy(carray + eltsize * j, tmp, eltsize);
+        }
+    }
+}
+
 /* vim: set shiftwidth=4 tabstop=8: */
diff --git a/puzzles.h b/puzzles.h
index e05a3e4..1c3ae59 100644
--- a/puzzles.h
+++ b/puzzles.h
@@ -223,6 +223,9 @@ unsigned char *hex2bin(const char *in, int outlen);
 void game_mkhighlight(frontend *fe, float *ret,
                       int background, int highlight, int lowlight);
 
+/* Randomly shuffles an array of items. */
+void shuffle(void *array, int nelts, int eltsize, random_state *rs);
+
 /*
  * version.c
  */
-- 
2.11.0