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# XPath parsing
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import copy
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from Parser import Parser
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class XpathElem:
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def __init__(self, name, value=None, attrs=None, is_attr=False,
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is_ptr=False):
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if attrs == None: attrs = []
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self.name = name
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self.value = value
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self.attrs = attrs
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self.is_attr = is_attr
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self.is_ptr = is_ptr
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def __repr__(self):
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str_ = ''
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if self.is_attr: str_ += '@'
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str_ += self.name
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if self.attrs != []: str_ += repr(self.attrs)
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if self.value != None: str_ += '='+repr(self.value)
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if self.is_ptr: str_ += '->'
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return str_
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def __eq__(self, other): return self.__dict__ == other.__dict__
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def value(path): return path[-1].value
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def set_value(path, value): path[-1].value = value
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def backward_id(elem):
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if len(elem.attrs) >= 1 and value(elem.attrs[0]) == None and\
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len(elem.attrs[0]) == 1: return elem.attrs[0]
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else: return None
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class XpathParser(Parser):
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def _main(self):
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self._match_str('/') # optional leading /
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return self._path()
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def _path(self):
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tree = []
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trailing_slash = False
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while True:
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# Split path
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if self._match_str('{'):
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paths = []
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while True:
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paths.append(tree + self._path())
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if not self._match_str(','): break
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self._match_str('}', required=True)
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tree = paths[0] # just use first subpath for now
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break # nothing allowed after split path
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elem = XpathElem(is_attr=self._match_str('@'),
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name=self._match_re(r'[\w.*]+', required=True))
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# Attrs
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if self._match_str('['):
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elem.attrs = []
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while True:
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path = self._path()
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if self._match_str('='):
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set_value(path, self._match_re(r'[\w.|]*'))
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elem.attrs.append(path)
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if not self._match_str(','): break
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self._match_str(']', required=True)
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elem.is_ptr = self._match_str('->')
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tree.append(elem)
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# Lookahead assertion
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if self._match_str('('):
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self._match_str('/', required=True) # next / is inside ()
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path = self._path()
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self._match_str(')', required=True)
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elem.attrs.append(path)
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tree += path
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if not self._match_str('/'): break
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# Expand * abbrs
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elem_idx = 0
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for elem in tree:
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id_ = backward_id(elem)
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if id_ != None: elem = id_[0]; offset = -2
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elif elem.is_ptr: offset = 2
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else: offset = 1
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before, abbr, after = elem.name.partition('*')
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if abbr != '':
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try: elem.name = before+tree[elem_idx+offset].name+after
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except IndexError: pass # no replacement elem
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elem_idx += 1
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return tree
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def parse(string): return XpathParser(string).parse()
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instance_level = 1
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def obj(path):
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obj_path = copy.deepcopy(path[:instance_level+1])
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obj_path[-1].is_ptr = False # prevent pointer w/o target
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return obj_path
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def set_id(path, id_, has_types=True):
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if has_types: id_level = instance_level
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else: id_level = 0
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path[id_level].attrs.append([XpathElem('id', id_, is_attr=True)])
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def is_id(path): return path[0].is_attr and path[0].name == 'id'
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def is_instance(elem): return elem.attrs != [] and is_id(elem.attrs[0])
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