From: Simon Tatham <anakin@pobox.com>
Date: Sun, 17 Jul 2005 12:12:16 +0000 (+0000)
Subject: Get rid of the malloc in shuffle(), by defining a subfunction
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=782a4f3fece388a3b5e541f4b1b11f86f69d5921;hp=a31934f233581da07153af6b4ee717f1e63387dd;p=sgt-puzzles.git

Get rid of the malloc in shuffle(), by defining a subfunction
memswap() which declares a fixed-size buffer on the stack and uses
it multiple times if necessary.

[originally from svn r6107]
---

diff --git a/misc.c b/misc.c
index b832ee0..5ad4d0b 100644
--- a/misc.c
+++ b/misc.c
@@ -194,21 +194,32 @@ void game_mkhighlight(frontend *fe, float *ret,
     }
 }
 
+void memswap(void *av, void *bv, int size)
+{
+    char tmpbuf[512];
+    char *a = av, *b = bv;
+
+    while (size > 0) {
+	int thislen = min(size, sizeof(tmpbuf));
+	memcpy(tmpbuf, a, thislen);
+	memcpy(a, b, thislen);
+	memcpy(b, tmpbuf, thislen);
+	a += thislen;
+	b += thislen;
+	size -= thislen;
+    }
+}
+
 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);
-        }
+        if (j != i)
+            memswap(carray + eltsize * i, carray + eltsize * j, eltsize);
     }
-    sfree(tmp);
 }
 
 void draw_rect_outline(frontend *fe, int x, int y, int w, int h, int colour)