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