ppapi/generators/idl_visitor.py

   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