.

wcfs/internal/xbtree.py

@@ -181,7 +181,29 @@ def StructureOf(node):
 # See top-level docstring for what topology is.
 def TopoEncode(tree):
     assert isinstance(tree, Tree)
-    topo = 'zzz'    # XXX
+    topo = ''
+
+    # breadth-first traversal of the tree with '/' injected in between layers
+    queue  = [tree, '/']
+    while 1:
+        x = queue.pop(0)
+        if x == '/':
+            if len(queue) == 0:
+                break   # it was last '/'
+            topo += '/'
+            queue.append('/')   # add / after all queued nodes of next layer
+            continue
+
+        node = x
+        assert isinstance(node, (Tree, Bucket))
+        tnode = ('T' if isinstance(node, Tree) else 'B') + \
+                    (','.join(['%d' % _ for _ in node.keyv]))
+        if len(topo) != 0 and topo[-1] != '/':
+            topo += '-'
+        topo += tnode
+
+        if isinstance(node, Tree):
+            queue += node.children
 
     if 1:   # debug
         t2 = TopoDecode(topo)
@@ -198,6 +220,18 @@ def TopoDecode(text):
 
 
 
+# _iterBFS iterates tree nodes in breadth-first order.
+def _iterBFS(tree): # -> i[] of tree nodes
+    assert isinstance(tree, Tree)
+    queue = [tree]
+    while len(queue) > 0:
+        node = queue.pop(0)
+        assert isinstance(node, (Tree, Bucket))
+        yield node
+        if isinstance(node, Tree):
+            queue += node.children
+
+
 # Restructure reorganizes BTree instance (not Tree) according to new structure.
 def Restructure(tree, newStructure):
     assert istree(tree)

wcfs/internal/xbtree_test.py

@@ -88,6 +88,7 @@ def test_topoEncoding():
     assert X(T([], B(1,3)))         == 'T/B1,3'
     assert X(T([], T([], B())))     == 'T/T/B'
 
+    # XXX two B under same T
     # XXX more
 
     assert X(T([3],