1 # Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 """ Visitor Object for traversing AST """ 6 7 # 8 # IDLVisitor 9 # 10 # The IDLVisitor class will traverse an AST truncating portions of the tree 11 # when 'VisitFilter' returns false. After the filter returns true, for each 12 # node, the visitor will call the 'Arrive' member passing in the node and 13 # and generic data object from the parent call. The returned value is then 14 # passed to all children who's results are aggregated into a list. The child 15 # results along with the original Arrive result are passed to the Depart 16 # function which returns the final result of the Visit. By default this is 17 # the exact value that was return from the original arrive. 18 # 19 20 class IDLVisitor(object): 21 def __init__(self): 22 pass 23 24 # Return TRUE if the node should be visited 25 def VisitFilter(self, node, data): 26 return True 27 28 def Visit(self, node, data): 29 if not self.VisitFilter(node, data): return None 30 31 childdata = [] 32 newdata = self.Arrive(node, data) 33 for child in node.GetChildren(): 34 ret = self.Visit(child, newdata) 35 if ret is not None: 36 childdata.append(ret) 37 return self.Depart(node, newdata, childdata) 38 39 def Arrive(self, node, data): 40 __pychecker__ = 'unusednames=node' 41 return data 42 43 def Depart(self, node, data, childdata): 44 __pychecker__ = 'unusednames=node,childdata' 45 return data 46
