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Edit File: xpath.py
# -*- test-case-name: twisted.words.test.test_xpath -*- # # Copyright (c) Twisted Matrix Laboratories. # See LICENSE for details. """ XPath query support. This module provides L{XPathQuery} to match L{domish.Element<twisted.words.xish.domish.Element>} instances against XPath-like expressions. """ from io import StringIO class LiteralValue(str): def value(self, elem): return self class IndexValue: def __init__(self, index): self.index = int(index) - 1 def value(self, elem): return elem.children[self.index] class AttribValue: def __init__(self, attribname): self.attribname = attribname if self.attribname == "xmlns": self.value = self.value_ns def value_ns(self, elem): return elem.uri def value(self, elem): if self.attribname in elem.attributes: return elem.attributes[self.attribname] else: return None class CompareValue: def __init__(self, lhs, op, rhs): self.lhs = lhs self.rhs = rhs if op == "=": self.value = self._compareEqual else: self.value = self._compareNotEqual def _compareEqual(self, elem): return self.lhs.value(elem) == self.rhs.value(elem) def _compareNotEqual(self, elem): return self.lhs.value(elem) != self.rhs.value(elem) class BooleanValue: """ Provide boolean XPath expression operators. @ivar lhs: Left hand side expression of the operator. @ivar op: The operator. One of C{'and'}, C{'or'}. @ivar rhs: Right hand side expression of the operator. @ivar value: Reference to the method that will calculate the value of this expression given an element. """ def __init__(self, lhs, op, rhs): self.lhs = lhs self.rhs = rhs if op == "and": self.value = self._booleanAnd else: self.value = self._booleanOr def _booleanAnd(self, elem): """ Calculate boolean and of the given expressions given an element. @param elem: The element to calculate the value of the expression from. """ return self.lhs.value(elem) and self.rhs.value(elem) def _booleanOr(self, elem): """ Calculate boolean or of the given expressions given an element. @param elem: The element to calculate the value of the expression from. """ return self.lhs.value(elem) or self.rhs.value(elem) def Function(fname): """ Internal method which selects the function object """ klassname = "_%s_Function" % fname c = globals()[klassname]() return c class _not_Function: def __init__(self): self.baseValue = None def setParams(self, baseValue): self.baseValue = baseValue def value(self, elem): return not self.baseValue.value(elem) class _text_Function: def setParams(self): pass def value(self, elem): return str(elem) class _Location: def __init__(self): self.predicates = [] self.elementName = None self.childLocation = None def matchesPredicates(self, elem): if self.elementName != None and self.elementName != elem.name: return 0 for p in self.predicates: if not p.value(elem): return 0 return 1 def matches(self, elem): if not self.matchesPredicates(elem): return 0 if self.childLocation != None: for c in elem.elements(): if self.childLocation.matches(c): return 1 else: return 1 return 0 def queryForString(self, elem, resultbuf): if not self.matchesPredicates(elem): return if self.childLocation != None: for c in elem.elements(): self.childLocation.queryForString(c, resultbuf) else: resultbuf.write(str(elem)) def queryForNodes(self, elem, resultlist): if not self.matchesPredicates(elem): return if self.childLocation != None: for c in elem.elements(): self.childLocation.queryForNodes(c, resultlist) else: resultlist.append(elem) def queryForStringList(self, elem, resultlist): if not self.matchesPredicates(elem): return if self.childLocation != None: for c in elem.elements(): self.childLocation.queryForStringList(c, resultlist) else: for c in elem.children: if isinstance(c, str): resultlist.append(c) class _AnyLocation: def __init__(self): self.predicates = [] self.elementName = None self.childLocation = None def matchesPredicates(self, elem): for p in self.predicates: if not p.value(elem): return 0 return 1 def listParents(self, elem, parentlist): if elem.parent != None: self.listParents(elem.parent, parentlist) parentlist.append(elem.name) def isRootMatch(self, elem): if ( self.elementName == None or self.elementName == elem.name ) and self.matchesPredicates(elem): if self.childLocation != None: for c in elem.elements(): if self.childLocation.matches(c): return True else: return True return False def findFirstRootMatch(self, elem): if ( self.elementName == None or self.elementName == elem.name ) and self.matchesPredicates(elem): # Thus far, the name matches and the predicates match, # now check into the children and find the first one # that matches the rest of the structure # the rest of the structure if self.childLocation != None: for c in elem.elements(): if self.childLocation.matches(c): return c return None else: # No children locations; this is a match! return elem else: # Ok, predicates or name didn't match, so we need to start # down each child and treat it as the root and try # again for c in elem.elements(): if self.matches(c): return c # No children matched... return None def matches(self, elem): if self.isRootMatch(elem): return True else: # Ok, initial element isn't an exact match, walk # down each child and treat it as the root and try # again for c in elem.elements(): if self.matches(c): return True # No children matched... return False def queryForString(self, elem, resultbuf): raise NotImplementedError("queryForString is not implemented for any location") def queryForNodes(self, elem, resultlist): # First check to see if _this_ element is a root if self.isRootMatch(elem): resultlist.append(elem) # Now check each child for c in elem.elements(): self.queryForNodes(c, resultlist) def queryForStringList(self, elem, resultlist): if self.isRootMatch(elem): for c in elem.children: if isinstance(c, str): resultlist.append(c) for c in elem.elements(): self.queryForStringList(c, resultlist) class XPathQuery: def __init__(self, queryStr): self.queryStr = queryStr # Prevent a circular import issue, as xpathparser imports this module. from twisted.words.xish.xpathparser import XPathParser, XPathParserScanner parser = XPathParser(XPathParserScanner(queryStr)) self.baseLocation = getattr(parser, "XPATH")() def __hash__(self): return self.queryStr.__hash__() def matches(self, elem): return self.baseLocation.matches(elem) def queryForString(self, elem): result = StringIO() self.baseLocation.queryForString(elem, result) return result.getvalue() def queryForNodes(self, elem): result = [] self.baseLocation.queryForNodes(elem, result) if len(result) == 0: return None else: return result def queryForStringList(self, elem): result = [] self.baseLocation.queryForStringList(elem, result) if len(result) == 0: return None else: return result __internedQueries = {} def internQuery(queryString): if queryString not in __internedQueries: __internedQueries[queryString] = XPathQuery(queryString) return __internedQueries[queryString] def matches(xpathstr, elem): return internQuery(xpathstr).matches(elem) def queryForStringList(xpathstr, elem): return internQuery(xpathstr).queryForStringList(elem) def queryForString(xpathstr, elem): return internQuery(xpathstr).queryForString(elem) def queryForNodes(xpathstr, elem): return internQuery(xpathstr).queryForNodes(elem)