# -*- 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 __future__ import absolute_import, division
from io import StringIO
from twisted.python.compat import StringType, unicode
class LiteralValue(unicode):
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 unicode(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(unicode(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, StringType):
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, StringType):
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)