'''
All KVM technology specefic functions are implemented inside this module
Two entites belong to this module: a Kvm hypervisor or a Kvm virtual machine
'''


from libvirtwrapper import *
from exceptions import *
import subprocess
import hashlib


class KvmHypervisor(LibvirtHypervisor):
    '''
    Base class of a Kvm Hypervisor
    This class have a attribute hv_type for tagging purposes
    '''
    _instance = None

    def __init__(self):
        super(KvmHypervisor, self).__init__('kvm')
        self.hv_type = 'KVM/QEMU'
    
    def __new__(cls, *args, **kwargs):
        '''
        .. note::
            We use singleton design pattern to force only a single instance
            of ourlibvirt hypervisor handle, it's essential since we connect
            with libvirt only on localhost so we must assure one single 
            connection to the hypervisor
        '''
        if cls._instance is None:
            cls._instance = super(KvmHypervisor, cls).__new__(cls, *args,
                                                                **kwargs)
        return cls._instance