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# Copyright 2012 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
""" Visitor Object for traversing AST """
#
# IDLVisitor
#
# The IDLVisitor class will traverse an AST truncating portions of the tree
# when 'VisitFilter' returns false. After the filter returns true, for each
# node, the visitor will call the 'Arrive' member passing in the node and
# and generic data object from the parent call. The returned value is then
# passed to all children who's results are aggregated into a list. The child
# results along with the original Arrive result are passed to the Depart
# function which returns the final result of the Visit. By default this is
# the exact value that was return from the original arrive.
#
class IDLVisitor(object):
def __init__(self):
pass
# Return TRUE if the node should be visited
def VisitFilter(self, node, data):
return True
def Visit(self, node, data):
if not self.VisitFilter(node, data): return None
childdata = []
newdata = self.Arrive(node, data)
for child in node.GetChildren():
ret = self.Visit(child, newdata)
if ret is not None:
childdata.append(ret)
return self.Depart(node, newdata, childdata)
def Arrive(self, node, data):
__pychecker__ = 'unusednames=node'
return data
def Depart(self, node, data, childdata):
__pychecker__ = 'unusednames=node,childdata'
return data
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