virt-manager/virtinst/xmlbuilder.py

#
# Base class for all VM devices
#
# Copyright 2008  Red Hat, Inc.
# Cole Robinson <crobinso@redhat.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free  Software Foundation; either version 2 of the License, or
# (at your option)  any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA 02110-1301 USA.

import copy
import os

import libxml2

from virtinst import util

# pylint: disable=W0212
# This whole file is calling around into non-public functions that we
# don't want regular API users to touch

_trackprops = bool("VIRTINST_TEST_TRACKPROPS" in os.environ)
_allprops = []
_seenprops = []


class _DocCleanupWrapper(object):
    def __init__(self, doc):
        self._doc = doc
    def __del__(self):
        self._doc.freeDoc()


class _CtxCleanupWrapper(object):
    def __init__(self, ctx):
        self._ctx = ctx
    def __del__(self):
        self._ctx.xpathFreeContext()
        self._ctx = None
    def __getattr__(self, attrname):
        return getattr(self._ctx, attrname)


def _indent(xmlstr, level):
    xml = ""
    if not xmlstr:
        return xml
    if not level:
        return xmlstr
    return "\n".join((" " * level + l) for l in xmlstr.splitlines())


def _tuplify_lists(*args):
    """
    Similar to zip(), but use None if lists aren't long enough, and
    don't skip any None list entry
    """
    args = [util.listify(l) for l in args]
    maxlen = max([len(l) for l in args])

    ret = []
    for idx in range(maxlen):
        tup = tuple()
        for l in args:
            tup += (idx >= len(l) and (None,) or (l[idx],))
        ret.append(tup)
    return ret


def _sanitize_libxml_xml(xml):
    # Strip starting <?...> line
    if xml.startswith("<?"):
        ignore, xml = xml.split("\n", 1)
    if not xml.endswith("\n") and xml.count("\n"):
        xml += "\n"
    return xml


def _get_xpath_node(ctx, xpath):
    node = ctx.xpathEval(xpath)
    return (node and node[0] or None)


def _build_xpath_node(ctx, xpath, addnode=None):
    """
    Build all nodes required to set an xpath. If we have XML <foo/>, and want
    to set xpath /foo/bar/baz@booyeah, we create node 'bar' and 'baz'
    returning the last node created.
    """
    parentpath = ""
    parentnode = None

    def prevSibling(node):
        parent = node.get_parent()
        if not parent:
            return None

        prev = None
        for child in parent.children:
            if child == node:
                return prev
            prev = child

        return None

    def make_node(parentnode, newnode):
        # Add the needed parent node, try to preserve whitespace by
        # looking for a starting TEXT node, and copying it
        def node_is_text(n):
            return bool(n and n.type == "text" and not n.content.count("<"))

        sib = parentnode.get_last()
        if not node_is_text(sib):
            # This case is when we add a child element to a node for the
            # first time, like:
            #
            # <features/>
            # to
            # <features>
            #   <acpi/>
            # </features>
            prevsib = prevSibling(parentnode)
            if node_is_text(prevsib):
                sib = libxml2.newText(prevsib.content)
            else:
                sib = libxml2.newText("\n")
            parentnode.addChild(sib)

        # This case is adding a child element to an already properly
        # spaced element. Example:
        # <features>
        #   <acpi/>
        # </features>
        # to
        # <features>
        #   <acpi/>
        #   <apic/>
        # </features>
        sib = parentnode.get_last()
        content = sib.content
        sib = sib.addNextSibling(libxml2.newText("  "))
        txt = libxml2.newText(content)

        sib.addNextSibling(newnode)
        newnode.addNextSibling(txt)
        return newnode

    nodelist = xpath.split("/")
    for idx in range(len(nodelist)):
        nodename = nodelist[idx]
        if not nodename:
            continue

        # If xpath is a node property, set it and move on
        if nodename.startswith("@"):
            nodename = nodename.strip("@")
            parentnode = parentnode.setProp(nodename, "")
            continue

        if not parentpath:
            parentpath = nodename
        else:
            parentpath += "/%s" % nodename

        # Node found, nothing to create for now
        node = _get_xpath_node(ctx, parentpath)
        if node:
            parentnode = node
            continue

        if not parentnode:
            raise RuntimeError("Could not find XML root node")

        # Remove conditional xpath elements for node creation
        if nodename.count("["):
            nodename = nodename[:nodename.index("[")]

        newnode = libxml2.newNode(nodename)
        parentnode = make_node(parentnode, newnode)

    if addnode:
        parentnode = make_node(parentnode, addnode)

    return parentnode


def _remove_xpath_node(ctx, xpath, dofree=True, root_name=None):
    """
    Remove an XML node tree if it has no content
    """
    curxpath = xpath

    while curxpath:
        is_orig = (curxpath == xpath)
        node = _get_xpath_node(ctx, curxpath)
        if curxpath.count("/"):
            curxpath, ignore = curxpath.rsplit("/", 1)
        else:
            curxpath = None

        if not node:
            continue

        if node.type not in ["attribute", "element"]:
            continue

        if node.type == "element" and (node.children or node.properties):
            # Only do a deep unlink if it was the original requested path
            if not is_orig:
                continue

        # Look for preceding whitespace and remove it
        white = node.get_prev()
        if white and white.type == "text" and not white.content.count("<"):
            white.unlinkNode()
            white.freeNode()

        # Don't unlink the root node. This is usually a programming error,
        # but the error usually cascades to a different spot and is hard
        # to pin down. With this we usually get invalid XML which is
        # easier to debug.
        if root_name and node.name == root_name:
            break

        node.unlinkNode()
        if dofree:
            node.freeNode()


class XMLProperty(property):
    def __init__(self, doc=None, xpath=None, name=None,
                 set_converter=None, validate_cb=None,
                 make_getter_xpath_cb=None, make_setter_xpath_cb=None,
                 is_bool=False, is_int=False, is_yesno=False,
                 clear_first=None, default_cb=None, default_name=None):
        """
        Set a XMLBuilder class property that represents a value in the
        <domain> XML. For example

        name = XMLProperty(get_name, set_name, xpath="/domain/name")

        When building XML from scratch (virt-install), name is a regular
        class property. When parsing and editting existing guest XML, we
        use the xpath value to map the name property to the underlying XML
        definition.

        @param doc: option doc string for the property
        @param xpath: xpath string which maps to the associated property
                      in a typical XML document
        @param name: Just a string to print for debugging, only needed
            if xpath isn't specified.
        @param set_converter: optional function for converting the property
            value from the virtinst API to the guest XML. For example,
            the Guest.memory API was once in MB, but the libvirt domain
            memory API is in KB. So, if xpath is specified, on a 'get'
            operation we convert the XML value with int(val) / 1024.
        @param validate_cb: Called once when value is set, should
            raise a RuntimeError if the value is not proper.
        @param make_getter_xpath_cb:
        @param make_setter_xpath_cb: Not all props map cleanly to a
            static xpath. This allows passing functions which generate
            an xpath for getting or setting.
        @param is_bool: Whether this is a boolean property in the XML
        @param is_int: Whethere this is an integer property in the XML
        @param is_yesno: Whethere this is a yes/no property in the XML
        @param clear_first: List of xpaths to unset before any 'set' operation.
            For those weird interdependent XML props like disk source type and
            path attribute.
        @param default_cb: If building XML from scratch, and this property
            is never explicitly altered, this function is called for setting
            a default value in the XML, and for any 'get' call before the
            first explicit 'set'.
        @param default_name: If the user does a set and passes in this
            value, instead use the value of default_cb()
        """

        self._xpath = xpath
        self._name = name or xpath
        if not self._name:
            raise RuntimeError("XMLProperty: name or xpath must be passed.")

        self._is_bool = is_bool
        self._is_int = is_int
        self._is_yesno = is_yesno

        self._xpath_for_getter_cb = make_getter_xpath_cb
        self._xpath_for_setter_cb = make_setter_xpath_cb

        self._validate_cb = validate_cb
        self._convert_value_for_setter_cb = set_converter
        self._setter_clear_these_first = clear_first or []
        self._default_cb = default_cb
        self._default_name = default_name

        if sum([int(bool(i)) for i in
               [self._is_bool, self._is_int, self._is_yesno]]) > 1:
            raise RuntimeError("Conflict property converter options.")

        if self._default_name and not self._default_cb:
            raise RuntimeError("default_name requires default_cb.")

        if _trackprops:
            _allprops.append(self)

        property.__init__(self, fget=self.getter, fset=self.setter)
        self.__doc__ = doc


    def __repr__(self):
        return "<XMLProperty %s %s>" % (str(self._name), id(self))


    ####################
    # Internal helpers #
    ####################

    def _findpropname(self, xmlbuilder):
        """
        Map the raw property() instance to the param name it's exposed
        as in the XMLBuilder class. This is just for debug purposes.
        """
        for key, val in xmlbuilder.all_xml_props().items():
            if val is self:
                return key
        raise RuntimeError("Didn't find expected property")

    def _xpath_for_getter(self, xmlbuilder):
        ret = self._xpath
        if self._xpath_for_getter_cb:
            ret = self._xpath_for_getter_cb(xmlbuilder)
        if ret is None:
            raise RuntimeError("%s: didn't generate any setter xpath." % self)
        return xmlbuilder.fix_relative_xpath(ret)
    def _xpath_for_setter(self, xmlbuilder):
        ret = self._xpath
        if self._xpath_for_setter_cb:
            ret = self._xpath_for_setter_cb(xmlbuilder)
        if ret is None:
            raise RuntimeError("%s: didn't generate any setter xpath." % self)
        return xmlbuilder.fix_relative_xpath(ret)


    def _convert_value_for_setter(self, xmlbuilder):
        # Convert from API value to XML value
        val = self._nonxml_fget(xmlbuilder)
        if self._default_name and val == self._default_name:
            val = self._default_cb(xmlbuilder)
        elif self._is_yesno:
            if val is not None:
                val = bool(val) and "yes" or "no"

        if self._convert_value_for_setter_cb:
            val = self._convert_value_for_setter_cb(xmlbuilder, val)
        return val

    def _build_node_list(self, xmlbuilder, xpath):
        """
        Build list of nodes that the passed xpaths reference
        """
        root_ctx = getattr(xmlbuilder, "_xml_ctx")
        nodes = _get_xpath_node(root_ctx, xpath)
        return util.listify(nodes)

    def _build_clear_list(self, xmlbuilder, setternode):
        """
        Build a list of nodes that we should erase first before performing
        a set operation. But we don't want to unset a node that we are
        just going to 'set' on top of afterwards, so skip those ones.
        """
        root_ctx = getattr(xmlbuilder, "_xml_ctx")
        clear_nodes = []

        for cpath in self._setter_clear_these_first:
            cpath = xmlbuilder.fix_relative_xpath(cpath)
            cnode = _get_xpath_node(root_ctx, cpath)
            if not cnode:
                continue
            if setternode and setternode.nodePath() == cnode.nodePath():
                continue
            clear_nodes.append(cnode)
        return clear_nodes


    def _convert_get_value(self, val):
        if self._default_name and val == self._default_name:
            ret = val
        elif self._is_bool:
            ret = bool(val)
        elif self._is_int and val is not None:
            intkwargs = {}
            if "0x" in str(val):
                intkwargs["base"] = 16
            ret = int(val, **intkwargs)
        elif self._is_yesno and val is not None:
            ret = bool(val == "yes")
        else:
            ret = val
        return ret

    def _prop_is_unset(self, xmlbuilder):
        propstore = getattr(xmlbuilder, "_propstore")
        propname = self._findpropname(xmlbuilder)
        return (propname not in propstore)

    def _set_default(self, xmlbuilder):
        """
        Encode the property default into the XML and propstore, but
        only if a default is registered, and only if the property was
        not already explicitly set by the API user.

        This is called during the get_xml_config process and shouldn't
        be called from outside this file.
        """
        if not self._prop_is_unset(xmlbuilder):
            return
        if not self._default_cb:
            return
        if self._default_cb(xmlbuilder) is None:
            return
        self.setter(xmlbuilder, self.getter(xmlbuilder), validate=False)

    def _nonxml_fset(self, xmlbuilder, val):
        """
        This stores the value in XMLBuilder._propstore
        dict as propname->value. This saves us from having to explicitly
        track every variable.
        """
        propstore = getattr(xmlbuilder, "_propstore")
        proporder = getattr(xmlbuilder, "_proporder")

        if _trackprops and self not in _seenprops:
            _seenprops.append(self)
        propname = self._findpropname(xmlbuilder)
        propstore[propname] = val

        if propname in proporder:
            proporder.remove(propname)
        proporder.append(propname)

    def _nonxml_fget(self, xmlbuilder):
        """
        The flip side to nonxml_fset, fetch the value from
        XMLBuilder._propstore
        """
        propstore = getattr(xmlbuilder, "_propstore")
        propname = self._findpropname(xmlbuilder)
        unset = (propname not in propstore)
        if unset and self._default_cb:
            if self._default_name:
                return self._default_name
            return self._default_cb(xmlbuilder)
        return propstore.get(propname, None)

    def _clear(self, xmlbuilder):
        self.setter(xmlbuilder, None)


    ##################################
    # The actual getter/setter impls #
    ##################################

    def getter(self, xmlbuilder):
        if xmlbuilder._xml_ctx is None:
            fgetval = self._nonxml_fget(xmlbuilder)
            return self._convert_get_value(fgetval)

        xpath = self._xpath_for_getter(xmlbuilder)
        node = _get_xpath_node(xmlbuilder._xml_ctx, xpath)

        if not node:
            return self._convert_get_value(None)

        content = node.content
        if self._is_bool:
            content = True
        return self._convert_get_value(content)

    def setter(self, xmlbuilder, val, call_fset=True, validate=True):
        if call_fset:
            if validate and self._validate_cb:
                self._validate_cb(xmlbuilder, val)
            self._nonxml_fset(xmlbuilder, val)

        root_node = getattr(xmlbuilder, "_xml_node")
        if root_node is None:
            return

        xpath = self._xpath_for_setter(xmlbuilder)
        setval = self._convert_value_for_setter(xmlbuilder)
        node = _get_xpath_node(xmlbuilder._xml_ctx, xpath)
        clearlist = self._build_clear_list(xmlbuilder, node)

        node_map = []
        if clearlist:
            node_map += _tuplify_lists(clearlist, None, "")
        node_map += [(node, setval, xpath)]

        for node, val, use_xpath in node_map:
            if node:
                use_xpath = node.nodePath()

            if val is None or val is False:
                _remove_xpath_node(root_node, use_xpath,
                                   root_name=root_node.name)
                continue

            if not node:
                node = _build_xpath_node(root_node, use_xpath)

            if val is True:
                # Boolean property, creating the node is enough
                continue
            node.setContent(util.xml_escape(str(val)))


class XMLBuilder(object):
    """
    Base for all classes which build or parse domain XML
    """
    # Order that we should apply values to the XML. Keeps XML generation
    # consistent with what the test suite expects.
    _XML_PROP_ORDER = []

    # Absolute xpath this object is rooted at
    _XML_ROOT_XPATH = None

    def __init__(self, conn, parsexml=None, parsexmlnode=None):
        """
        Initialize state

        @param conn: libvirt connection to validate device against
        @type conn: VirtualConnection
        @param parsexml: Optional XML string to parse
        @type parsexml: C{str}
        @param parsexmlnode: Option xpathNode to use
        """
        self.conn = conn

        xpath = self._XML_ROOT_XPATH
        if xpath is None or not xpath.startswith("/"):
            raise RuntimeError("xpath=%s must start with /" % xpath)

        self._xml_root_name = xpath.split("/")[-1]
        self._xml_indent = (xpath.count("/") - 1) * 2
        self._xml_dump_xpath = xpath
        self._xml_root_xpath = ""

        self._xml_node = None
        self._xml_ctx = None
        self._xml_root_doc = None
        self._propstore = {}
        self._proporder = []

        if parsexml or parsexmlnode:
            self._parsexml(parsexml, parsexmlnode)


    ##############
    # Public API #
    ##############

    def copy(self):
        ret = copy.copy(self)
        ret._propstore = ret._propstore.copy()
        ret._proporder = ret._proporder[:]
        return ret

    def set_new_xml(self, xml):
        self._parsexml(xml, None)

    def set_root_xpath(self, xpath):
        self._xml_root_xpath = xpath
        xmlprops = self.all_xml_props()

        for propname in self._XML_PROP_ORDER:
            if propname in xmlprops:
                continue
            for prop in util.listify(getattr(self, propname)):
                prop.set_root_xpath(xpath)

    def get_root_xpath(self):
        return self._xml_root_xpath

    def fix_relative_xpath(self, xpath):
        if not self._xml_root_xpath:
            return xpath
        return "%s%s" % (self._xml_root_xpath, xpath.strip("."))

    def get_xml_config(self):
        data = self._prepare_get_xml()
        try:
            return self._do_get_xml_config()
        finally:
            self._finish_get_xml(data)

    def clear(self):
        for prop in self.all_xml_props().values():
            prop._clear(self)

    def _do_get_xml_config(self):
        """
        Construct and return object xml

        @return: object xml representation as a string
        @rtype: str
        """
        if self._xml_ctx:
            node = _get_xpath_node(self._xml_ctx, self._xml_dump_xpath)
            if not node:
                ret = ""
            else:
                ret = _sanitize_libxml_xml(node.serialize())
        else:
            xmlstub = self._make_xml_stub()
            if xmlstub is None:
                return None

            ret = self._add_parse_bits(xmlstub)
            if ret == xmlstub:
                ret = ""

        if ret and self._xml_root_name == "domain" and not ret.endswith("\n"):
            ret += "\n"
        return ret


    #######################
    # Internal helper API #
    #######################

    def _is_parse(self):
        return bool(self._xml_node or self._xml_ctx)


    ###################
    # Child overrides #
    ###################

    def set_defaults(self):
        pass

    def validate(self):
        pass

    def _prepare_get_xml(self):
        return None
    def _finish_get_xml(self, data):
        ignore = data


    ########################
    # Internal XML parsers #
    ########################

    def _make_xml_stub(self):
        return _indent("<%s/>" % (self._xml_root_name), self._xml_indent)

    def _add_child(self, parent_xpath, dev):
        """
        Insert the passed XMLBuilder object into our XML document at the
        specified path
        """
        dev.set_new_xml(dev.get_xml_config())
        newnode = dev._xml_node
        ret = _build_xpath_node(self._xml_ctx, parent_xpath, newnode)
        return ret

    def _remove_child_xpath(self, xpath):
        _remove_xpath_node(self._xml_ctx, xpath, dofree=False)
        self._set_xml_context()

    def _set_xml_context(self):
        doc = self._xml_node.doc
        ctx = _CtxCleanupWrapper(doc.xpathNewContext())
        ctx.setContextNode(self._xml_node)
        self._xml_ctx = ctx

    def _parsexml(self, xml, node):
        if xml:
            doc = libxml2.parseDoc(xml)
            self._xml_root_doc = _DocCleanupWrapper(doc)
            self._xml_node = doc.children
            self._xml_dump_xpath = "."

            # This just stores a reference to our root doc wrapper in
            # the root node, so when the node goes away it triggers
            # auto free'ing of the doc
            self._xml_node.virtinst_root_doc = self._xml_root_doc
        else:
            self._xml_node = node
            self._xml_dump_xpath = self._XML_ROOT_XPATH

        self._set_xml_context()

    def all_xml_props(self):
        ret = {}
        for c in reversed(type.mro(self.__class__)[:-1]):
            for key, val in c.__dict__.items():
                if val.__class__ is XMLProperty:
                    ret[key] = val
        return ret

    def _do_add_parse_bits(self, xml, node):
        # Set all defaults if the properties have one registered
        xmlprops = self.all_xml_props()
        for prop in xmlprops.values():
            prop._set_default(self)

        # Default props alter our _propstore. But at this point _propstore
        # is empty, there's nothing for us to do, so exit early
        if not self._propstore:
            return xml

        # Unindent XML
        indent = 0
        if xml:
            for c in xml:
                if c != " ":
                    break
                indent += 1
            xml = "\n".join([l[indent:] for l in xml.splitlines()])

        # Parse the XML into our internal state. Use the raw
        # _parsexml so we don't hit Guest parsing into its internal state
        XMLBuilder._parsexml(self, xml, node)

        # Set up preferred XML ordering
        do_order = self._proporder[:]
        for key in reversed(self._XML_PROP_ORDER):
            if key in do_order:
                do_order.remove(key)
                do_order.insert(0, key)
            elif key not in xmlprops:
                do_order.insert(0, key)

        # Alter the XML
        for key in do_order:
            if key in xmlprops:
                xmlprops[key].setter(self, self._propstore[key],
                                     validate=False)
            else:
                for obj in util.listify(getattr(self, key)):
                    if self._xml_root_xpath and not obj._xml_root_xpath:
                        obj._xml_root_xpath = self._xml_root_xpath
                    obj._add_parse_bits(xml=None, node=self._xml_node)

        return _indent(self._do_get_xml_config(), indent)

    def _add_parse_bits(self, xml, node=None):
        """
        Callback that adds the implicitly tracked XML properties to
        the manually generated xml. This should only exist until all
        classes are converted to all parsing all the time
        """
        if self._is_parse():
            return xml

        origproporder = self._proporder[:]
        origpropstore = self._propstore.copy()
        try:
            return self._do_add_parse_bits(xml, node)
        finally:
            self._xml_root_doc = None
            self._xml_node = None
            self._xml_ctx = None
            self._proporder = origproporder
            self._propstore = origpropstore