virt-manager/virtinst/xmlapi.py
Cole Robinson b2b9d7d366 devices: char: Add CharSource
Move all ./source handling into CharSource, which will be reused by
other device classes as well. This requires us to add ../ handling
into our xmlapi xpath engine
2019-05-14 11:57:50 -04:00

395 lines
13 KiB
Python

#
# XML API wrappers
#
# This work is licensed under the GNU GPLv2 or later.
# See the COPYING file in the top-level directory.
import libxml2
from . import util
# pylint: disable=protected-access
class _XPathSegment(object):
"""
Class representing a single 'segment' of an xpath string. For example,
the xpath:
./qemu:foo/bar[1]/baz[@somepro='someval']/@finalprop
will be split into the following segments:
#1: nodename=., fullsegment=.
#2: nodename=foo, nsname=qemu, fullsegment=qemu:foo
#3: nodename=bar, condition_num=1, fullsegment=bar[1]
#4: nodename=baz, condition_prop=somepro, condition_val=someval,
fullsegment=baz[@somepro='somval']
#5: nodename=finalprop, is_prop=True, fullsegment=@finalprop
"""
def __init__(self, fullsegment):
self.fullsegment = fullsegment
self.nodename = fullsegment
self.condition_prop = None
self.condition_val = None
self.condition_num = None
if "[" in self.nodename:
self.nodename, cond = self.nodename.strip("]").split("[")
if "=" in cond:
(cprop, cval) = cond.split("=")
self.condition_prop = cprop.strip("@")
self.condition_val = cval.strip("'")
elif cond.isdigit():
self.condition_num = int(cond)
self.is_prop = self.nodename.startswith("@")
if self.is_prop:
self.nodename = self.nodename[1:]
self.nsname = None
if ":" in self.nodename:
self.nsname, self.nodename = self.nodename.split(":")
class _XPath(object):
"""
Helper class for performing manipulations of XPath strings. Splits
the xpath into segments.
"""
def __init__(self, fullxpath):
self.fullxpath = fullxpath
self.segments = []
for s in self.fullxpath.split("/"):
if s == "..":
# Resolve and flatten .. in xpaths
self.segments = self.segments[:-1]
continue
self.segments.append(_XPathSegment(s))
self.is_prop = self.segments[-1].is_prop
self.propname = (self.is_prop and self.segments[-1].nodename or None)
if self.is_prop:
self.segments = self.segments[:-1]
self.xpath = self.join(self.segments)
@staticmethod
def join(segments):
return "/".join(s.fullsegment for s in segments)
def parent_xpath(self):
return self.join(self.segments[:-1])
class _XMLBase(object):
NAMESPACES = {}
@classmethod
def register_namespace(cls, nsname, uri):
cls.NAMESPACES[nsname] = uri
def copy_api(self):
raise NotImplementedError()
def count(self, xpath):
raise NotImplementedError()
def _find(self, fullxpath):
raise NotImplementedError()
def _node_tostring(self, node):
raise NotImplementedError()
def _node_get_text(self, node):
raise NotImplementedError()
def _node_set_text(self, node, setval):
raise NotImplementedError()
def _node_get_property(self, node, propname):
raise NotImplementedError()
def _node_set_property(self, node, propname, setval):
raise NotImplementedError()
def _node_new(self, xpathseg, parentnode):
raise NotImplementedError()
def _node_add_child(self, parentxpath, parentnode, newnode):
raise NotImplementedError()
def _node_remove_child(self, parentnode, childnode):
raise NotImplementedError()
def _node_from_xml(self, xml):
raise NotImplementedError()
def _node_has_content(self, node):
raise NotImplementedError()
def _node_get_name(self, node):
raise NotImplementedError()
def node_clear(self, xpath):
raise NotImplementedError()
def _sanitize_xml(self, xml):
raise NotImplementedError()
def get_xml(self, xpath):
node = self._find(xpath)
if node is None:
return ""
return self._sanitize_xml(self._node_tostring(node))
def get_xpath_content(self, xpath, is_bool):
node = self._find(xpath)
if node is None:
return None
if is_bool:
return True
xpathobj = _XPath(xpath)
if xpathobj.is_prop:
return self._node_get_property(node, xpathobj.propname)
return self._node_get_text(node)
def set_xpath_content(self, xpath, setval):
node = self._find(xpath)
if setval is False:
# Boolean False, means remove the node entirely
self.node_force_remove(xpath)
elif setval is None:
if node is not None:
self._node_set_content(xpath, node, None)
self._node_remove_empty(xpath)
else:
if node is None:
node = self._node_make_stub(xpath)
if setval is True:
# Boolean property, creating the node is enough
return
self._node_set_content(xpath, node, setval)
def node_add_xml(self, xml, xpath):
newnode = self._node_from_xml(xml)
parentnode = self._node_make_stub(xpath)
self._node_add_child(xpath, parentnode, newnode)
def node_force_remove(self, fullxpath):
"""
Remove the element referenced at the passed xpath, regardless
of whether it has children or not, and then clean up the XML
chain
"""
xpathobj = _XPath(fullxpath)
parentnode = self._find(xpathobj.parent_xpath())
childnode = self._find(fullxpath)
if parentnode is None or childnode is None:
return
self._node_remove_child(parentnode, childnode)
def validate_root_name(self, expected_root_name):
rootname = self._node_get_name(self._find("."))
if rootname == expected_root_name:
return
raise RuntimeError(
_("XML did not have expected root element name '%s', found '%s'") %
(expected_root_name, rootname))
def _node_set_content(self, xpath, node, setval):
xpathobj = _XPath(xpath)
if setval is not None:
setval = str(setval)
if xpathobj.is_prop:
self._node_set_property(node, xpathobj.propname, setval)
else:
self._node_set_text(node, setval)
def _node_make_stub(self, fullxpath):
"""
Build all nodes for the passed xpath. For example, if XML is <foo/>,
and xpath=./bar/@baz, after this function the XML will be:
<foo>
<bar baz=''/>
</foo>
And the node pointing to @baz will be returned, for the caller to
do with as they please.
There's also special handling to ensure that setting
xpath=./bar[@baz='foo']/frob will create
<bar baz='foo'>
<frob></frob>
</bar>
Even if <bar> didn't exist before. So we fill in the dependent property
expression values
"""
xpathobj = _XPath(fullxpath)
parentxpath = "."
parentnode = self._find(parentxpath)
if parentnode is None:
raise RuntimeError("programming error: "
"Did not find XML root node for xpath=%s" % fullxpath)
for xpathseg in xpathobj.segments[1:]:
oldxpath = parentxpath
parentxpath += "/%s" % xpathseg.fullsegment
tmpnode = self._find(parentxpath)
if tmpnode is not None:
# xpath node already exists, nothing to create yet
parentnode = tmpnode
continue
newnode = self._node_new(xpathseg, parentnode)
self._node_add_child(oldxpath, parentnode, newnode)
parentnode = newnode
# For a conditional xpath like ./foo[@bar='baz'],
# we also want to implicitly set <foo bar='baz'/>
if xpathseg.condition_prop:
self._node_set_property(parentnode, xpathseg.condition_prop,
xpathseg.condition_val)
return parentnode
def _node_remove_empty(self, fullxpath):
"""
Walk backwards up the xpath chain, and remove each element
if it doesn't have any children or attributes, so we don't
leave stale elements in the XML
"""
xpathobj = _XPath(fullxpath)
segments = xpathobj.segments[:]
parent = None
while segments:
xpath = _XPath.join(segments)
segments.pop()
child = parent
parent = self._find(xpath)
if parent is None:
break
if child is None:
continue
if self._node_has_content(child):
break
self._node_remove_child(parent, child)
def node_is_text(n):
return bool(n and n.type == "text")
class _Libxml2API(_XMLBase):
def __init__(self, xml):
_XMLBase.__init__(self)
self._doc = libxml2.parseDoc(xml)
self._ctx = self._doc.xpathNewContext()
self._ctx.setContextNode(self._doc.children)
for key, val in self.NAMESPACES.items():
self._ctx.xpathRegisterNs(key, val)
def __del__(self):
self._doc.freeDoc()
self._doc = None
self._ctx.xpathFreeContext()
self._ctx = None
def _sanitize_xml(self, xml):
# Strip starting <?...> line
if xml.startswith("<?"):
ignore, xml = xml.split("\n", 1)
if not xml.endswith("\n") and "\n" in xml:
xml += "\n"
return xml
def copy_api(self):
return _Libxml2API(self._doc.children.serialize())
def _find(self, fullxpath):
xpath = _XPath(fullxpath).xpath
node = self._ctx.xpathEval(xpath)
return (node and node[0] or None)
def count(self, xpath):
return len(self._ctx.xpathEval(xpath))
def _node_tostring(self, node):
return node.serialize()
def _node_from_xml(self, xml):
return libxml2.parseDoc(xml).children
def _node_get_text(self, node):
return node.content
def _node_set_text(self, node, setval):
if setval is not None:
setval = util.xml_escape(setval)
node.setContent(setval)
def _node_get_property(self, node, propname):
prop = node.hasProp(propname)
if prop:
return prop.content
def _node_set_property(self, node, propname, setval):
if setval is None:
prop = node.hasProp(propname)
if prop:
prop.unlinkNode()
prop.freeNode()
else:
node.setProp(propname, util.xml_escape(setval))
def _node_new(self, xpathseg, parentnode):
newnode = libxml2.newNode(xpathseg.nodename)
if not xpathseg.nsname:
return newnode
def _find_parent_ns():
parent = parentnode
while parent:
for ns in util.listify(parent.nsDefs()):
if ns.name == xpathseg.nsname:
return ns
parent = parent.get_parent()
ns = _find_parent_ns()
if not ns:
ns = newnode.newNs(
self.NAMESPACES[xpathseg.nsname], xpathseg.nsname)
newnode.setNs(ns)
return newnode
def node_clear(self, xpath):
node = self._find(xpath)
if node:
propnames = [p.name for p in (node.properties or [])]
for p in propnames:
node.unsetProp(p)
node.setContent(None)
def _node_has_content(self, node):
return node.type == "element" and (node.children or node.properties)
def _node_get_name(self, node):
return node.name
def _node_remove_child(self, parentnode, childnode):
node = childnode
# Look for preceding whitespace and remove it
white = node.get_prev()
if node_is_text(white):
white.unlinkNode()
white.freeNode()
node.unlinkNode()
node.freeNode()
if all([node_is_text(n) for n in parentnode.children]):
parentnode.setContent(None)
def _node_add_child(self, parentxpath, parentnode, newnode):
ignore = parentxpath
if not node_is_text(parentnode.get_last()):
prevsib = parentnode.get_prev()
if node_is_text(prevsib):
newlast = libxml2.newText(prevsib.content)
else:
newlast = libxml2.newText("\n")
parentnode.addChild(newlast)
endtext = parentnode.get_last().content
parentnode.addChild(libxml2.newText(" "))
parentnode.addChild(newnode)
parentnode.addChild(libxml2.newText(endtext))
XMLAPI = _Libxml2API