Package logilab :: Package common :: Module visitor
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Source Code for Module logilab.common.visitor

  1  # copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved. 
  2  # contact http://www.logilab.fr/ -- mailto:contact@logilab.fr 
  3  # 
  4  # This file is part of logilab-common. 
  5  # 
  6  # logilab-common is free software: you can redistribute it and/or modify it under 
  7  # the terms of the GNU Lesser General Public License as published by the Free 
  8  # Software Foundation, either version 2.1 of the License, or (at your option) any 
  9  # later version. 
 10  # 
 11  # logilab-common is distributed in the hope that it will be useful, but WITHOUT 
 12  # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS 
 13  # FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more 
 14  # details. 
 15  # 
 16  # You should have received a copy of the GNU Lesser General Public License along 
 17  # with logilab-common.  If not, see <http://www.gnu.org/licenses/>. 
 18  """A generic visitor abstract implementation. 
 19   
 20   
 21   
 22   
 23  """ 
 24  __docformat__ = "restructuredtext en" 
 25   
26 -def no_filter(_):
27 return 1
28 29 # Iterators ###################################################################
30 -class FilteredIterator(object):
31
32 - def __init__(self, node, list_func, filter_func=None):
33 self._next = [(node, 0)] 34 if filter_func is None: 35 filter_func = no_filter 36 self._list = list_func(node, filter_func)
37
38 - def __next__(self):
39 try: 40 return self._list.pop(0) 41 except : 42 return None
43 44 next = __next__
45 46 # Base Visitor ################################################################
47 -class Visitor(object):
48
49 - def __init__(self, iterator_class, filter_func=None):
50 self._iter_class = iterator_class 51 self.filter = filter_func
52
53 - def visit(self, node, *args, **kargs):
54 """ 55 launch the visit on a given node 56 57 call 'open_visit' before the beginning of the visit, with extra args 58 given 59 when all nodes have been visited, call the 'close_visit' method 60 """ 61 self.open_visit(node, *args, **kargs) 62 return self.close_visit(self._visit(node))
63
64 - def _visit(self, node):
65 iterator = self._get_iterator(node) 66 n = next(iterator) 67 while n: 68 result = n.accept(self) 69 n = next(iterator) 70 return result
71
72 - def _get_iterator(self, node):
73 return self._iter_class(node, self.filter)
74
75 - def open_visit(self, *args, **kargs):
76 """ 77 method called at the beginning of the visit 78 """ 79 pass
80
81 - def close_visit(self, result):
82 """ 83 method called at the end of the visit 84 """ 85 return result
86 87 # standard visited mixin ######################################################
88 -class VisitedMixIn(object):
89 """ 90 Visited interface allow node visitors to use the node 91 """
92 - def get_visit_name(self):
93 """ 94 return the visit name for the mixed class. When calling 'accept', the 95 method <'visit_' + name returned by this method> will be called on the 96 visitor 97 """ 98 try: 99 return self.TYPE.replace('-', '_') 100 except: 101 return self.__class__.__name__.lower()
102
103 - def accept(self, visitor, *args, **kwargs):
104 func = getattr(visitor, 'visit_%s' % self.get_visit_name()) 105 return func(self, *args, **kwargs)
106
107 - def leave(self, visitor, *args, **kwargs):
108 func = getattr(visitor, 'leave_%s' % self.get_visit_name()) 109 return func(self, *args, **kwargs)
110