minor improvements

[moebius2.git] / mgraph.c

diff --git a/mgraph.c b/mgraph.c
index 23a10e352ffa69bc91f9a4c9185fd911e90dbfd1..4b708e5bd12c247ca21e78e6a1d082217908702d 100644 (file)
--- a/mgraph.c
+++ b/mgraph.c
@@ -24,3 +24,15 @@ int edge_end2(unsigned v1, int e) {
   
   return x | y;
 }
+
+static const unsigned reverse[2][V6]= {{ 3, 4, 5, 0, 1, 2 },
+                                      { 3, 2, 1, 0, 5, 4 }};
+
+int edge_reverse(int v1, int e) {
+  unsigned x2;
+  int flip;
+
+  x2= (v1 & XMASK) + dx[(v1 >> YSHIFT) & 1][e];
+  flip= !!(x2 & ~XMASK);
+  return reverse[flip][e];
+}