Package paramiko :: Module resource |
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# Source Code for Module paramiko.resource

     1  # Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com>
     2  #
     3  # This file is part of paramiko.
     4  #
     5  # Paramiko is free software; you can redistribute it and/or modify it under the
     6  # terms of the GNU Lesser General Public License as published by the Free
     7  # Software Foundation; either version 2.1 of the License, or (at your option)
     8  # any later version.
     9  #
    10  # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
    11  # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
    12  # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
    13  # details.
    14  #
    15  # You should have received a copy of the GNU Lesser General Public License
    16  # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
    17  # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
    18
    19  """
    20  Resource manager.
    21  """
    22
    23  import weakref
    24
    25
    26 -class ResourceManager (object):
    27      """
    28      A registry of objects and resources that should be closed when those
    29      objects are deleted.
    30
    31      This is meant to be a safer alternative to python's C{__del__} method,
    32      which can cause reference cycles to never be collected.  Objects registered
    33      with the ResourceManager can be collected but still free resources when
    34      they die.
    35
    36      Resources are registered using L{register}, and when an object is garbage
    37      collected, each registered resource is closed by having its C{close()}
    38      method called.  Multiple resources may be registered per object, but a
    39      resource will only be closed once, even if multiple objects register it.
    40      (The last object to register it wins.)
    41      """
    42
    43 -    def __init__(self):
    44          self._table = {}
    45
    46 -    def register(self, obj, resource):
    47          """
    48          Register a resource to be closed with an object is collected.
    49
    50          When the given C{obj} is garbage-collected by the python interpreter,
    51          the C{resource} will be closed by having its C{close()} method called.
    52          Any exceptions are ignored.
    53
    54          @param obj: the object to track
    55          @type obj: object
    56          @param resource: the resource to close when the object is collected
    57          @type resource: object
    58          """
    59          def callback(ref):
    60              try:
    61                  resource.close()
    62              except:
    63                  pass
    64              del self._table[id(resource)]
    65
    66          # keep the weakref in a table so it sticks around long enough to get
    67          # its callback called. :)
    68          self._table[id(resource)] = weakref.ref(obj, callback)
    69
    70
    71  # singleton
    72  ResourceManager = ResourceManager()
    73