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# XPath-based XML tree manipulation
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from copy import deepcopy
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from xml.dom import Node
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from Parser import Parser
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import xml_util
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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:
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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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while True:
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elem = XpathElem(is_attr=self._match_str('@'), name=self._fields())
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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('='): set_value(path, self._value())
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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 _fields(self):
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if self._match_str('{'):
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tree = []
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while True:
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tree.append(self._field())
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if not self._match_str(','): break
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self._match_str('}', required=True)
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tree = tuple(tree)
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tree = tree[0] # just use first field for now
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else: tree = self._field()
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return tree
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def _field(self):
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return self._name()
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def _name(self): return self._match_re(r'[\w.*]+', required=True)
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def _value(self): return self._match_re(r'[\w.|]+', required=True)
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instance_level = 1
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def obj(path):
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obj_path = 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 get(doc, path, create=False, last_only=None, parent=None):
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# Warning: The last_only optimization may put data that should be together
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# into separate nodes
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if parent == None: parent = doc.documentElement
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if last_only == None: last_only = create
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elem_idx = 0
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for elem in path:
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# Find possible matches
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children = []
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if elem.is_attr:
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child = parent.getAttributeNode(elem.name)
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if child != None: children = [child]
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elif elem.name == '.': children = [parent]
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else: children = xml_util.by_tag_name(parent, elem.name, last_only)
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# Check each match
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node = None
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for child in children:
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is_match = elem.value == None or xml_util.value(child) == elem.value
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for attr in elem.attrs:
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if not is_match: break
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is_match = get(doc, attr, False, last_only, child) != None
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if is_match: node = child; break
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# Create node
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if node == None:
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if not create: return None
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if elem.is_attr:
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parent.setAttribute(elem.name, '')
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node = parent.getAttributeNode(elem.name)
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else: node = parent.appendChild(doc.createElement(elem.name))
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if elem.value != None: xml_util.set_value(doc, node, elem.value)
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for attr in elem.attrs: get(doc, attr, create, last_only, node)
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# Follow pointer
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if elem.is_ptr:
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path = deepcopy(path[elem_idx+1:]) # rest of path
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id_elem = backward_id(path[instance_level])
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if id_elem != None:
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# backward (child-to-parent) pointer with target ID attr
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set_value(id_elem, xml_util.get_id(node))
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else: # forward (parent-to-child) pointer
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id_ = xml_util.value(node)
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obj_path = obj(path) # target object
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if id_ == None or get(doc, obj_path, False, True) == None:
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# no target or target attrs don't match
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if not create: return None
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# Use last target object's ID + 1
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obj_path[-1].attrs = [] # just get by tag name
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last = get(doc, obj_path, False, True)
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if last != None: id_ = str(int(xml_util.get_id(last)) + 1)
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else: id_ = '0'
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# Will append if target attrs didn't match. Place ! in XPath
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# after element to fork at to avoid this.
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xml_util.set_value(doc, node, id_)
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else: last_only = False
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set_id(path, id_)
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return get(doc, path, create, last_only)
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parent = node
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elem_idx += 1
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return parent
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