shithub: puzzles

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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]

--- a/misc.c

+++ b/misc.c

@@ -194,21 +194,32 @@

     }

 }

+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)