Add DLTree()

This patch adds a double-linked tree class for use in storing the
library.  This class can walk backwards from a leaf node when
walk_backwards is called.

libsaria/trees.py

@@ -47,6 +47,30 @@ class Tree(dict):
 		if len(path) > 1:
 			child.insert(path[1:])
 
+class DLTree(Tree):
+	def __init__(self):
+		Tree.__init__(self)
+		self.parent = None
+
+	def walk_backwards(self, child = None):
+		key = None
+		if child != None:
+			key = [item[0] for item in self.items() if id(item[1]) == id(child)]
+			if self.parent == None:
+				return key
+		ret = self.parent.walk_backwards(self)
+		if key:
+			return ret + key
+		else:
+			return ret
+
+	def insert(self, path):
+		child = self.__insert__(path)
+		child.parent = self
+		if len(path) > 1:
+			return child.insert(path[1:])
+		return child
+
 
 class FSTree(Tree):
 	def __init__(self):

tests/trees.py

@@ -7,11 +7,22 @@ from libsaria import trees
 #tree.insert(["home", "bjschuma", "Videos"])
 #tree.insert(["home", "other", "Music"])
 
-from libsaria import path
-tree = path.make_tree("/home/bjschuma/Music")
+#from libsaria import path
+#tree = path.make_tree("/home/bjschuma/Music")
 #print tree
 
-print tree.value
+#print tree.value
 #tree.disp()
-for path in tree.walk():
-	print path
+#for path in tree.walk():
+#	print path
+
+
+tree = trees.DLTree()
+
+n = tree.insert(["a", "b", "c", "d"])
+o = tree.insert(["a", "b", "c", "e"])
+p = tree.insert(["f", "g", "h", "i"])
+tree.disp()
+print n.walk_backwards()
+print o.walk_backwards()
+print p.walk_backwards()