.

wcfs/internal/xbtree.py

@@ -456,7 +456,12 @@ def _walkBFS(tree): # i[] of [](of nodes on each level)
     for level in __walkBFS(tree):
         yield tuple(rn.node for rn in level)
 
-def __walkBFS(tree): # i[] of [](of _NodeInRange)
+# _zwalkBFS, similarly to _walkBFS, walks ZODB BTree in breadth-first order layer by layer.
+def _zwalkBFS(ztree): # i[] of [](of nodes on each level)
+    for zlevel in __zwalkBFS(ztree):
+        yield tuple(rn.node for rn in zlevel)
+
+def __walkBFS(tree): # i[] of [](of _NodeInRange on each level)
     assert isinstance(tree, Tree)
     currentq = []
     nextq    = [_NodeInRange(_Range(-inf,+inf), tree)]
@@ -474,8 +479,7 @@ def __walkBFS(tree): # i[] of [](of _NodeInRange)
                 for i in range(len(rv)):
                     nextq.append(_NodeInRange(_Range(*rv[i]), rn.node.children[i]))
 
-# _zwalkBFS, similarly to _walkBFS, walks ZODB BTree in breadth-first order layer by layer.
-def _zwalkBFS(ztree): # i[] of [](of nodes on each level)
+def __zwalkBFS(ztree): # i[] of [](of _NodeInRange on each level)
     _ = _zclassify(ztree)
     assert _.is_ztree
 

wcfs/internal/xbtree_test.py

@@ -28,6 +28,26 @@ from BTrees import check as bcheck
 from persistent import Persistent
 inf = float('inf')
 
+# build ztree with known degenerate topology, see:
+# https://github.com/zopefoundation/ZODB/commit/6cd24e99f89b
+# https://github.com/zopefoundation/BTrees/blob/4.7.2-1-g078ba60/BTrees/tests/testBTrees.py#L20
+def buildDegenerateZTree():
+    ztree, keys = testBTrees.DegenerateBTree("testBasicOps")._build_degenerate_tree()
+    assert keys == [1, 3, 5, 7, 11]
+
+    T = xbtree.Tree
+    B = xbtree.Bucket
+    assert xbtree.StructureOf(ztree) == T([4],
+                                          T([2],
+                                               T([], B(1)), T([], B(3))),
+                                          T([],
+                                               T([6, 10],
+                                                   T([], T([], B(5))),
+                                                   T([], B(7)),
+                                                   T([], B(11))) ))
+    return ztree
+
+
 def test_structureOf():
     T = xbtree.Tree
     B = xbtree.Bucket
@@ -42,10 +62,7 @@ def test_structureOf():
     assert xbtree.StructureOf(t) == T([], B(10))
 
     # known degenerate topology, see:
-    # https://github.com/zopefoundation/ZODB/commit/6cd24e99f89b
-    # https://github.com/zopefoundation/BTrees/blob/4.7.2-1-g078ba60/BTrees/tests/testBTrees.py#L20
-    t, keys = testBTrees.DegenerateBTree("testBasicOps")._build_degenerate_tree()
-    assert keys == [1, 3, 5, 7, 11]
+    t = buildDegenerateZTree()
     assert xbtree.StructureOf(t) == T([4],
                                       T([2],
                                            T([], B(1)), T([], B(3))),
@@ -400,6 +417,9 @@ def test_walkBFS():
     B = xbtree.Bucket
     R = xbtree._Range
 
+    # XXX ø
+    # XXX 1 k->v
+
     bl = B(); br = B()
     tl = T([], bl)
     tr = T([], br)
@@ -430,6 +450,48 @@ def test_walkBFS():
 
     # XXX more tests?
 
+def test_zwalkBFS():
+    zt = buildDegenerateZTree()
+
+    # T return kind + keys of a ztree node
+    def T(ztree):
+        assert isinstance(ztree, IITreeSet)
+        kind, keys, kids = zbcheck.crack_btree(ztree)
+        return (kind, keys)
+
+    # B returns keys from zbucket node
+    def B(zbucket):
+        assert isinstance(zbucket, IISet)
+        keys, _ = zbcheck.crack_bucket(zbucket)
+        return keys
+
+    zwalkv = list(xbtree.__zwalkBFS(zt))
+    assert len(zwalkv) == 6         # [-∞,∞)T4,
+                                    #   [-∞,4)T2,  [4,∞)T
+                                    #     [-∞,2)T, [2,4)T, [4,∞)T6,10
+                                    #       [-∞,2)B1, [2,4)B3, [4,6)T, [6,10)T, [10,∞]T
+                                    #         [4,6)T, [6,10)B7, [10,∞)B11
+                                    #           [4,6)B5
+
+    _ = zwalkv[0]   # [-∞,∞)T4,
+    assert len(_) == 1
+    assert _[0].range   == R(-inf, inf)
+    assert T(_[0].node) == (BTREE_NORMAL, [4])
+
+    _ = zwalkv[1]   # [-∞,4)T2,  [4,∞)T
+    assert len(_) == 2
+    assert _[0].range   == R(-inf, 4)
+    assert T(_[0].node) == (BTREE_NORMAL, [2])
+    assert _[1].range   == R(4, inf)
+    assert T(_[1].node) == (BTREE_NORMAL, [])
+
+    _ = zwalkv[2]   # [-∞,2)T, [2,4)T, [4,∞)T6,10
+    assert len(_) == 3
+
+
+    # XXX
+
+
 
 def test_keyvSliceBy():
     X = xbtree._keyvSliceBy