python: solve ComputerSystem issues

Added ComputerSystem module to lmi.providers with convenience functions
allowing to obtain instance from CIMOM and check for its correctness
when inspecting client's input.

Also removed obsoleted system_name property out of BaseConfiguration
class.

3 files changed, 177 insertions, 6 deletions

diff --git a/src/python/lmi/base/BaseConfiguration.py b/src/python/lmi/base/BaseConfiguration.py
index 8333cca..baabcc6 100644
--- a/src/python/lmi/base/BaseConfiguration.py
+++ b/src/python/lmi/base/BaseConfiguration.py
@@ -72,6 +72,10 @@ class BaseConfiguration(Singleton):
         There should be only one instance of this class.
     """
 
+    #: Allow to access global configuration object also from lmi.providers
+    #: subpackage where ``get_instance()`` can not be used.
+    #: This variable shall be set in ``__init__()`` method.
+    INSTANCE = None
     CONFIG_DIRECTORY_TEMPLATE_TOPLEVEL = '/etc/openlmi/'
     CONFIG_DIRECTORY_TEMPLATE_PROVIDER = '/etc/openlmi/%(provider_prefix)s/'
     CONFIG_FILE_PATH_TEMPLATE_TOPLEVEL = \
@@ -152,6 +156,7 @@ class BaseConfiguration(Singleton):
         self.config = ConfigParser.SafeConfigParser(
                 defaults=self.default_options())
         self.load()
+        BaseConfiguration.INSTANCE = self
 
     def add_listener(self, callback):
         """
@@ -199,11 +204,6 @@ class BaseConfiguration(Singleton):
         return self.config.get('CIM', 'SystemClassName')
 
     @property
-    def system_name(self):
-        """ Return SystemName of OpenLMI provider. """
-        return socket.getfqdn()
-
-    @property
     def logging_level(self):
         """ Return name of logging level in lower case. """
         return self.config.get('Log', 'Level').lower()
diff --git a/src/python/lmi/providers/ComputerSystem.py b/src/python/lmi/providers/ComputerSystem.py
new file mode 100644
index 0000000..0b347f8
--- /dev/null
+++ b/src/python/lmi/providers/ComputerSystem.py
@@ -0,0 +1,154 @@
+# -*- encoding: utf-8 -*-
+# Software Management Providers
+#
+# Copyright (C) 2012-2013 Red Hat, Inc.  All rights reserved.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+"""
+Just a common functionality related to associated class ``CIM_ComputerSystem``.
+"""
+
+import pywbem
+
+from lmi.base.BaseConfiguration import BaseConfiguration
+from lmi.providers import cmpi_logging
+from lmi.software import util
+
+class UninitializedError(Exception):
+    """
+    Raised when the initialization parameter is not passed to function upon
+    its first invocation.
+    """
+    pass
+
+class NotInstrumentedError(Exception):
+    """
+    Raised when some CIM class is not instrumented in current *CIMOM*.
+    """
+    pass
+
+@cmpi_logging.trace_function
+def get_path(env=None):
+    """
+    Get the instance name of preferred computer system. Instance is cached,
+    so the broker is accessed just upon the first invocation. Confiruation
+    instance must be instantiated before this function is called.
+
+    :param ProviderEnvironment env: Provider environment, taken from CIMOM
+        callback (e.g. ``get_providers()``). It's needed just upon the first
+        invocation.
+    :returns: Instance of ``CIM_ComputerSystem``. Exact subclass is defined
+        in configuration file.
+    :rtype: :py:class:`pywbem.CIMInstanceName`
+    """
+    if not hasattr(get_path, '_instance'):
+        if env is None:
+            raise UninitializedError("get_computer_system_path() needs to be"
+                    " given environment object at first invocation")
+        inames = [ i for i in env.get_cimom_handle().EnumerateInstanceNames(
+                        "root/cimv2",
+                        BaseConfiguration.INSTANCE.system_class_name) ]
+        if len(inames) < 1:
+            raise NotInstrumentedError("CIM_ComputerSystem class is not"
+                    " instrumented or EnumerateInstanceNames() operation"
+                    " is not supported")
+        get_path._instance = inames[0]
+    return get_path._instance.copy()
+
+@cmpi_logging.trace_function
+def get_system_name(env=None):
+    """
+    Get the name of system contained in a ``Name`` property of instance of
+    ``CIM_ComputerSystem``.
+
+    :param ProviderEnvironment env: Provider environment, taken from CIMOM
+        callback (e.g. ``get_providers()``). It's needed only upon a
+        first invocation of this function or
+        :py:func:`get_computer_system_path`.
+    :returns: Name of computer system.
+    :rtype: string
+    """
+    return get_path(env)["Name"]
+
+@cmpi_logging.trace_function
+def check_path(env, system, prop_name):
+    """
+    Checks instance name of ``CIM_ComputerSystem``. If the object path matches
+    this computer system, ``True`` is returned. Exception is raised otherwise.
+    Especially useful when checking arguments of instance's method taking
+    reference to computer system an argument.
+
+    :param system: Instance name of computer system to check.
+    :type system: :py:class:`pywbem.CIMInstanceName`
+    :param string prop_name: Name of argument or property referring to the object
+        path being checked. This is used in exception messages upon
+        unsuccessful checks.
+    :returns: ``True``
+    :rtype: boolean
+    """
+    if not isinstance(system, pywbem.CIMInstanceName):
+        raise pywbem.CIMError(pywbem.CIM_ERR_INVALID_PARAMETER,
+                "\"%s\" must be a CIMInstanceName" % prop_name)
+    our_system = get_path(env)
+    ch = env.get_cimom_handle()
+    if system.namespace != our_system.namespace:
+        raise pywbem.CIMError(pywbem.CIM_ERR_NOT_FOUND,
+                'Namespace of "%s" does not match "%s"' % (
+                    prop_name, our_system.namespace))
+    if not ch.is_subclass(our_system.namespace,
+            sub=system.classname,
+            super="CIM_ComputerSystem"):
+        raise pywbem.CIMError(pywbem.CIM_ERR_NOT_FOUND,
+                "Class of \"%s\" must be a sublass of %s" % (
+                    prop_name, our_system.classname))
+    if not 'CreationClassName' in system or not 'Name' in system:
+        raise pywbem.CIMError(pywbem.CIM_ERR_NOT_FOUND,
+                "\"%s\" is missing one of keys", prop_name)
+    if not ch.is_subclass(our_system.namespace,
+            sub=system['CreationClassName'],
+            super="CIM_ComputerSystem"):
+        raise pywbem.CIMError(pywbem.CIM_ERR_NOT_FOUND,
+                "CreationClassName of \"%s\" must be a sublass of %s" % (
+                prop_name, our_system.classname))
+    if not util.is_this_system(system['Name']):
+        raise pywbem.CIMError(pywbem.CIM_ERR_NOT_FOUND,
+                "Name of \"%s\" does not match \"%s\"" % (
+                prop_name, our_system['Name']))
+    return True
+
+@cmpi_logging.trace_function
+def check_path_property(env, op, prop_name):
+    """
+    This checks, whether the object path contains correct instance name of
+    ``CIM_ComputerSystem`` corresponding to this system. If not, an exception
+    is raised.
+
+    Example usage in ``get_instance()`` method of provider: ::
+
+        # body of get_instance() method of some association class having
+        # *System* property referring to an instance of *CIM_ComputerSystem*.
+        ComputerSystem.check_path_property(env, model, "System")
+
+    :param op: Object path to check.
+    :param string prop_name: Name of property referring to the object path being
+        checked. This is used in exception messages when check is unsuccessful.
+    :returns: ``True``
+    :rtype: boolean
+    """
+    if not prop_name in op:
+        raise pywbem.CIMError(pywbem.CIM_ERR_INVALID_PARAMETER,
+                "Missing %s key property!" % prop_name)
+    return check_path(env, op[prop_name], prop_name)
+
diff --git a/src/python/lmi/providers/__init__.py b/src/python/lmi/providers/__init__.py
index baebcdb..7aec342 100644
--- a/src/python/lmi/providers/__init__.py
+++ b/src/python/lmi/providers/__init__.py
@@ -18,10 +18,13 @@
 #
 # Authors: Michal Minar <miminar@redhat.com>
 #
-
 """
 Common utilities for OpenLMI python providers.
 """
+
+import socket
+from lmi.base.BaseConfiguration import BaseConfiguration
+
 def parse_instance_id(instance_id, classname=None):
     """
     Parse InstanceID, check it has LMI:<classname>:<ID> format and return
@@ -40,3 +43,17 @@ def parse_instance_id(instance_id, classname=None):
     if classname and real_classname.lower() != classname.lower():
         return None
     return parts[2]
+
+def is_this_system(system_name):
+    """
+    Return ``True`` if given *system_name* matches the hostname of currently
+    running system.
+
+    Global configuration object must be initialized before calling this
+    function.
+
+    :rtype: boolean
+    """
+    return (  socket.gethostbyaddr(system_name)[0]
+           == socket.gethostbyaddr(
+               BaseConfiguration.INSTANCE.system_class_name)[0])