X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=mgraph.c;h=4b708e5bd12c247ca21e78e6a1d082217908702d;hb=23c346bb18366c8e9509743aacc5d777bd7f85cb;hp=cf57624262ae1c00224f6566cc112a81e6f50fb6;hpb=70df58c53bdd2c2b0de6a93e6c7c480730e6732a;p=moebius2.git

diff --git a/mgraph.c b/mgraph.c
index cf57624..4b708e5 100644
--- a/mgraph.c
+++ b/mgraph.c
@@ -4,19 +4,35 @@
 
 #include "mgraph.h"
 
-static const unsigned dx[V6]= {  +1,  +1,   0,  -1,  -1,   0  },
-                      dy[V6]= {   0, -Y1, -Y1,   0, +Y1, +Y1  };
+static const unsigned dx[2][V6]= {{  +1,   0,  -1,  -1,  -1,   0  },
+				  {  +1,  +1,   0,  -1,   0,  +1  }},
+                      dy[V6]=     {   0, -Y1, -Y1,   0, +Y1, +Y1  };
 
 int edge_end2(unsigned v1, int e) {
   unsigned x, y;
 
   y= (v1 & YMASK) + dy[e];
-  if (y & ~YMASK) return -1;
+  if (y >= Y*Y1) return -1;
 
-  x= (v1 & XMASK) + dx[e];
+  x= (v1 & XMASK) + dx[(v1 >> YSHIFT) & 1][e];
   if (x & ~XMASK) {
+    //int orgy= y;
     y= (Y-1)*Y1 - y;
     x &= XMASK;;
+    //printf("%40s %02x -%d-> %02x  (was %02x) \n", "", v1, e, x|y, x|orgy);
   }
+  
   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];
+}