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introspection.py

# -*- coding: utf-8 -*-

# slip.dbus.introspection -- access dbus introspection data
#
# Copyright © 2011 Red Hat, Inc.
#
# 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, see <http://www.gnu.org/licenses/>.
#
# Authors:
# Nils Philippsen <nils@redhat.com>

"""Classes and functions to easily access DBus introspection data."""

from __future__ import absolute_import

from xml.etree.ElementTree import ElementTree
from io import StringIO
from six import with_metaclass

class IElemMeta(type):
    """Metaclass for introspection elements.

Sets elemname class member automatically from class name if not set
    explicitly. Registers classes for their element names."""

elemnames_to_classes = {}

@classmethod
    def clsname_to_elemname(cls, clsname):
        elemname = ""
        for c in clsname:
            c_lower = c.lower()
            if c_lower != c:
                if len(elemname):
                    elemname += "_"
            elemname += c_lower
        return elemname

def __new__(cls, name, bases, dct):
        if name == "IElem":
            return type.__new__(cls, name, bases, dct)

if 'elemname' not in dct:
            if not name.startswith("IElem"):
                raise TypeError(
                    "Class '%s' needs to set elemname (or be called "
                    "'IElem...'))" % name)
            dct['elemname'] = IElemMeta.clsname_to_elemname(name[5:])

elemname = dct['elemname']

if elemname in IElemMeta.elemnames_to_classes:
            raise TypeError(
                "Class '%s' tries to register duplicate elemname '%s'" %
                (name, elemname))

kls = type.__new__(cls, name, bases, dct)

IElemMeta.elemnames_to_classes[elemname] = kls

return kls

class IElem(with_metaclass(IElemMeta, object)):
    """Base class for introspection elements."""

def __new__(cls, elem, parent=None):
        kls = IElemMeta.elemnames_to_classes.get(
            elem.tag, IElemMeta.elemnames_to_classes[None])
        return super(IElem, cls).__new__(kls, elem, parent)

def __init__(self, elem, parent=None):
        self.elem = elem
        self.parent = parent
        self.child_elements = [IElem(c, parent=self) for c in elem]

def __str__(self):
        s = "%s %r" % (self.elemname if self.elemname else "unknown:%s" %
            self.elem.tag, self.attrib)
        for c in self.child_elements:
            for cc in str(c).split("\n"):
                s += "\n  %s" % (cc)
        return s

@property
    def attrib(self):
        return self.elem.attrib

class IElemUnknown(IElem):
    """Catch-all for unknown introspection elements."""

elemname = None

class IElemNameMixin(object):
    """Mixin for introspection elements with names."""

@property
    def name(self):
        return self.attrib['name']

class IElemNode(IElem, IElemNameMixin):
    """Introspection node."""

def __init__(self, elem, parent=None):
        super(IElemNode, self).__init__(elem, parent)

self.child_nodes = [
            c for c in self.child_elements if isinstance(c, IElemNode)]

class IElemInterface(IElem):
    """Introspection interface."""

class IElemMethod(IElem):
    """Introspection interface method."""

class IElemArg(IElem):
    """Introspection method argument."""

class IElemSignal(IElem, IElemNameMixin):
    """Introspection interface signal."""

def introspect(string_or_file):
    tree = ElementTree()
    # assume string if read() method doesn't exist, works for string, unicode,
    # dbus.String
    if not hasattr(string_or_file, "read"):
        string_or_file = StringIO(string_or_file)
    xml_root = tree.parse(string_or_file)
    elem_root = IElem(xml_root)
    return elem_root

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