Don't roll a b block if it doesn't make sense to

This added a pathological case where each iteration we'd roll a b block
into place, just to have to do a giant rotate to move all the accumulated
b blocks over to make room for the a block that should have been inserted
next.

1 files changed, 2 insertions, 6 deletions

diff --git a/wikisort.c b/wikisort.c
index 2efa3ad..b2de063 100644
--- a/wikisort.c
+++ b/wikisort.c
@@ -96,18 +96,14 @@ static size_t roll(struct blockarray *a, struct blockarray *b,
 	size_t bwidth, size_t width, char **mina, cmpfun cmp)
 {
 	size_t iters = 0;
-	char  *prevb;
-
-	do {
+	while (b->blocks && cmp(b->base , *mina + bwidth - width) < 0) {
 		swap(a->base, b->base, bwidth);
 		if (*mina == a->base) *mina = b->base;
-		prevb = a->base;
 		a->base += bwidth;
 		b->base += bwidth;
 		b->blocks--;
 		iters++;
-	} while (b->blocks && cmp(prevb + bwidth - width, *mina) < 0);
-
+	}
 	return iters;
 }