X "B:" indicates ø bucket with k&b, "B" - ø bucket with only keys

wcfs/internal/xbtree.py

@@ -187,7 +187,10 @@ class Bucket(object):
             kvv = ['%s' % k for k in b.keyv]
         else:
             assert len(b.keyv) == len(b.valuev)
-            kvv = ['%s:%s' % (k,v) for (k,v) in zip(b.keyv, b.valuev)]
+            if len(b.keyv) == 0:
+                kvv = [':']
+            else:
+                kvv = ['%s:%s' % (k,v) for (k,v) in zip(b.keyv, b.valuev)]
         return "B" + ','.join(kvv)
     __repr__ = __str__
 
@@ -762,16 +765,19 @@ def TopoEncode(tree, vencode=lambda v: '%d' % v):
             tnode = ('T' if isinstance(node, Tree) else 'B')
             if isinstance(node, Bucket) and node.valuev is not None:
                 # bucket with key and values
-                assert len(node.valuev) == len(node.keyv)
-                vtxtv = []
-                for v in node.valuev:
-                    vtxt = vencode(v)
-                    assert ' ' not in vtxt
-                    assert ':' not in vtxt
-                    assert ',' not in vtxt
-                    assert '-' not in vtxt
-                tnode += ','.join(['%d:%s' % (k,vtxt)
-                                for (k,vtxt) in zip(node.keyv, vtxtv)])
+                assert len(node.keyv) == len(node.valuev)
+                if len(node.keyv) == 0:
+                    tnode += ':'
+                else:
+                    vtxtv = []
+                    for v in node.valuev:
+                        vtxt = vencode(v)
+                        assert ' ' not in vtxt
+                        assert ':' not in vtxt
+                        assert ',' not in vtxt
+                        assert '-' not in vtxt
+                    tnode += ','.join(['%d:%s' % (k,vtxt)
+                                    for (k,vtxt) in zip(node.keyv, vtxtv)])
             else:
                 # tree or bucket with keys
                 tnode += ','.join(['%d' % _ for _ in node.keyv])
@@ -820,14 +826,15 @@ def TopoDecode(text, vdecode=int):
             withV = (typ is Bucket and ':' in tkeys)
             keyv  = []
             valuev= [] if withV else None
-            for tkey in tkeyv:
-                ktxt = tkey
-                if withV:
-                    ktxt, vtxt = tkey.split(':')
-                    v = vdecode(vtxt)
-                    valuev.append(v)
-                k = int(ktxt)
-                keyv.append(k)
+            if tkeys != ':': # "B:" indicates ø bucket with values
+                for tkey in tkeyv:
+                    ktxt = tkey
+                    if withV:
+                        ktxt, vtxt = tkey.split(':')
+                        v = vdecode(vtxt)
+                        valuev.append(v)
+                    k = int(ktxt)
+                    keyv.append(k)
 
             if typ is Bucket:
                 node = Bucket(keyv, valuev)