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75 lines
2.4 KiB
75 lines
2.4 KiB
15 years ago
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##############################################################################
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#
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# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
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#
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# This software is subject to the provisions of the Zope Public License,
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# Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
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# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
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# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
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# FOR A PARTICULAR PURPOSE
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#
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##############################################################################
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__version__='$Revision: 1.6 $'[11:-2]
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from SelectCompiler import ast
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ListType = type([])
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TupleType = type(())
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SequenceTypes = (ListType, TupleType)
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class MutatingWalker:
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def __init__(self, visitor):
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self.visitor = visitor
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self._cache = {}
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def defaultVisitNode(self, node, walker=None, exclude=None):
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for name, child in node.__dict__.items():
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if exclude is not None and name in exclude:
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continue
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v = self.dispatchObject(child)
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if v is not child:
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# Replace the node.
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node.__dict__[name] = v
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return node
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def visitSequence(self, seq):
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res = seq
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for idx in range(len(seq)):
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child = seq[idx]
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v = self.dispatchObject(child)
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if v is not child:
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# Change the sequence.
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if type(res) is ListType:
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res[idx : idx + 1] = [v]
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else:
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res = res[:idx] + (v,) + res[idx + 1:]
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return res
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def dispatchObject(self, ob):
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'''
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Expected to return either ob or something that will take
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its place.
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'''
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if isinstance(ob, ast.Node):
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return self.dispatchNode(ob)
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elif type(ob) in SequenceTypes:
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return self.visitSequence(ob)
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else:
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return ob
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def dispatchNode(self, node):
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klass = node.__class__
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meth = self._cache.get(klass, None)
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if meth is None:
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className = klass.__name__
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meth = getattr(self.visitor, 'visit' + className,
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self.defaultVisitNode)
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self._cache[klass] = meth
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return meth(node, self)
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def walk(tree, visitor):
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return MutatingWalker(visitor).dispatchNode(tree)
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