.

wcfs/internal/xbtree.py

@@ -79,6 +79,7 @@ from __future__ import print_function, absolute_import
 
 from BTrees import check as bcheck
 from golang import panic
+from golang.gcompat import qq
 import itertools
 import re
 inf = float('inf')
@@ -178,7 +179,7 @@ def StructureOf(node):
 
 # TopoEncode returns topology encoding for internal structure of the tree.
 #
-# See top-level docstring for what topology is.
+# See top-level docstring for description of topology encoding.
 def TopoEncode(tree):
     assert isinstance(tree, Tree)
     topo = ''
@@ -214,9 +215,54 @@ def TopoEncode(tree):
 
 # TopoDecode decodes topology-encoded text into Tree structure.
 #
-# XXX see -> ?
+# See top-level docstring for description of topology encoding.
+class TopoDecodeError(Exception):
+    pass
 def TopoDecode(text):
-    return Tree([], Bucket())   # XXX stub
+    levelv = text.split('/')    # T3/T-T/B1-T5/B-B7,8,9  -> T3 T-T B1-T5 B-B7,8,9
+
+    # build nodes from bottop-up
+    currentv = [] # of nodes on current level (that we are building)
+    bottomq  = [] # of nodes below current level that we are building
+                  # shrinks as fifo as nodes added to currentv link to bottom
+    while len(levelv) > 0:
+        level  = levelv.pop()       # e.g. B1-T5
+        tnodev = level.split('-')   # e.g. B1 T5
+        bottomq  = currentv
+        currentv = []
+        for tnode in tnodev:
+            if   tnode[:1] == 'T':
+                typ = Tree
+            elif tnode[:1] == 'B':
+                typ = Bucket
+            else:
+                raise TopoDecodeError("incorrect node %s: unknown prefix" % qq(tnode))
+            tkeyv = tnode[1:].split(',')    # e.g. 7 8 9
+            keyv  = [int(_) for _ in tkeyv]
+            if typ is Bucket:
+                node = Bucket(*keyv)
+            else:
+                # Tree
+                nchild = len(keyv) + 1
+                if len(bottomq) < nchild:
+                    raise TopoDecodeError(
+                        "node %s at level %d: next level does not have enough children to link to" %
+                        (qq(tnode), len(levelv)+1))
+                children = bottomq[:nchild]
+                bottomq  = bottomq[nchild:]
+                node = Tree(keyv, *children)
+
+            currentv.append(node)
+
+        if len(bottomq) != 0:
+            raise TopoDecodeError("level %d does not link to all nodes in the next level" %
+                                  len(levelv+1))
+
+    if len(currentv) != 0:
+        raise TopoDecodeError("first level has %d entries; must be 1" % len(currentv))
+
+    root = currentv[0]
+    return root
 
 
 # Restructure reorganizes BTree instance (not Tree) according to new structure.

wcfs/internal/xbtree_test.py

@@ -63,7 +63,7 @@ def test_topoEncoding():
     def X(tree):
         topo = xbtree.TopoEncode(tree)
         t2   = xbtree.TopoDecode(topo)
-        #assert t2 == tree      # XXX reenable
+        assert t2 == tree
         return topo
 
     assert X(T([], B()))            == 'T/B'