Open Media Library Platform

Linux/lib/python2.7/site-packages/twisted/persisted/styles.py

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+# -*- test-case-name: twisted.test.test_persisted -*-
+# Copyright (c) Twisted Matrix Laboratories.
+# See LICENSE for details.
+
+
+
+"""
+Different styles of persisted objects.
+"""
+
+# System Imports
+import types
+import copy_reg
+import copy
+import inspect
+import sys
+
+try:
+    import cStringIO as StringIO
+except ImportError:
+    import StringIO
+
+# Twisted Imports
+from twisted.python import log
+from twisted.python import reflect
+
+oldModules = {}
+
+## First, let's register support for some stuff that really ought to
+## be registerable...
+
+def pickleMethod(method):
+    'support function for copy_reg to pickle method refs'
+    return unpickleMethod, (method.im_func.__name__,
+                             method.im_self,
+                             method.im_class)
+
+def unpickleMethod(im_name,
+                    im_self,
+                    im_class):
+    'support function for copy_reg to unpickle method refs'
+    try:
+        unbound = getattr(im_class,im_name)
+        if im_self is None:
+            return unbound
+        bound = types.MethodType(unbound.im_func, im_self, im_class)
+        return bound
+    except AttributeError:
+        log.msg("Method",im_name,"not on class",im_class)
+        assert im_self is not None,"No recourse: no instance to guess from."
+        # Attempt a common fix before bailing -- if classes have
+        # changed around since we pickled this method, we may still be
+        # able to get it by looking on the instance's current class.
+        unbound = getattr(im_self.__class__,im_name)
+        log.msg("Attempting fixup with",unbound)
+        if im_self is None:
+            return unbound
+        bound = types.MethodType(unbound.im_func, im_self, im_self.__class__)
+        return bound
+
+copy_reg.pickle(types.MethodType,
+                pickleMethod,
+                unpickleMethod)
+
+def pickleModule(module):
+    'support function for copy_reg to pickle module refs'
+    return unpickleModule, (module.__name__,)
+
+def unpickleModule(name):
+    'support function for copy_reg to unpickle module refs'
+    if name in oldModules:
+        log.msg("Module has moved: %s" % name)
+        name = oldModules[name]
+        log.msg(name)
+    return __import__(name,{},{},'x')
+
+
+copy_reg.pickle(types.ModuleType,
+                pickleModule,
+                unpickleModule)
+
+def pickleStringO(stringo):
+    'support function for copy_reg to pickle StringIO.OutputTypes'
+    return unpickleStringO, (stringo.getvalue(), stringo.tell())
+
+def unpickleStringO(val, sek):
+    x = StringIO.StringIO()
+    x.write(val)
+    x.seek(sek)
+    return x
+
+if hasattr(StringIO, 'OutputType'):
+    copy_reg.pickle(StringIO.OutputType,
+                    pickleStringO,
+                    unpickleStringO)
+
+def pickleStringI(stringi):
+    return unpickleStringI, (stringi.getvalue(), stringi.tell())
+
+def unpickleStringI(val, sek):
+    x = StringIO.StringIO(val)
+    x.seek(sek)
+    return x
+
+
+if hasattr(StringIO, 'InputType'):
+    copy_reg.pickle(StringIO.InputType,
+                pickleStringI,
+                unpickleStringI)
+
+class Ephemeral:
+    """
+    This type of object is never persisted; if possible, even references to it
+    are eliminated.
+    """
+
+    def __getstate__(self):
+        log.msg( "WARNING: serializing ephemeral %s" % self )
+        import gc
+        if '__pypy__' not in sys.builtin_module_names:
+            if getattr(gc, 'get_referrers', None):
+                for r in gc.get_referrers(self):
+                    log.msg( " referred to by %s" % (r,))
+        return None
+
+    def __setstate__(self, state):
+        log.msg( "WARNING: unserializing ephemeral %s" % self.__class__ )
+        self.__class__ = Ephemeral
+
+
+versionedsToUpgrade = {}
+upgraded = {}
+
+def doUpgrade():
+    global versionedsToUpgrade, upgraded
+    for versioned in versionedsToUpgrade.values():
+        requireUpgrade(versioned)
+    versionedsToUpgrade = {}
+    upgraded = {}
+
+def requireUpgrade(obj):
+    """Require that a Versioned instance be upgraded completely first.
+    """
+    objID = id(obj)
+    if objID in versionedsToUpgrade and objID not in upgraded:
+        upgraded[objID] = 1
+        obj.versionUpgrade()
+        return obj
+
+def _aybabtu(c):
+    """
+    Get all of the parent classes of C{c}, not including C{c} itself, which are
+    strict subclasses of L{Versioned}.
+
+    The name comes from "all your base are belong to us", from the deprecated
+    L{twisted.python.reflect.allYourBase} function.
+
+    @param c: a class
+    @returns: list of classes
+    """
+    # begin with two classes that should *not* be included in the
+    # final result
+    l = [c, Versioned]
+    for b in inspect.getmro(c):
+        if b not in l and issubclass(b, Versioned):
+            l.append(b)
+    # return all except the unwanted classes
+    return l[2:]
+
+class Versioned:
+    """
+    This type of object is persisted with versioning information.
+
+    I have a single class attribute, the int persistenceVersion.  After I am
+    unserialized (and styles.doUpgrade() is called), self.upgradeToVersionX()
+    will be called for each version upgrade I must undergo.
+
+    For example, if I serialize an instance of a Foo(Versioned) at version 4
+    and then unserialize it when the code is at version 9, the calls::
+
+      self.upgradeToVersion5()
+      self.upgradeToVersion6()
+      self.upgradeToVersion7()
+      self.upgradeToVersion8()
+      self.upgradeToVersion9()
+
+    will be made.  If any of these methods are undefined, a warning message
+    will be printed.
+    """
+    persistenceVersion = 0
+    persistenceForgets = ()
+
+    def __setstate__(self, state):
+        versionedsToUpgrade[id(self)] = self
+        self.__dict__ = state
+
+    def __getstate__(self, dict=None):
+        """Get state, adding a version number to it on its way out.
+        """
+        dct = copy.copy(dict or self.__dict__)
+        bases = _aybabtu(self.__class__)
+        bases.reverse()
+        bases.append(self.__class__) # don't forget me!!
+        for base in bases:
+            if 'persistenceForgets' in base.__dict__:
+                for slot in base.persistenceForgets:
+                    if slot in dct:
+                        del dct[slot]
+            if 'persistenceVersion' in base.__dict__:
+                dct['%s.persistenceVersion' % reflect.qual(base)] = base.persistenceVersion
+        return dct
+
+    def versionUpgrade(self):
+        """(internal) Do a version upgrade.
+        """
+        bases = _aybabtu(self.__class__)
+        # put the bases in order so superclasses' persistenceVersion methods
+        # will be called first.
+        bases.reverse()
+        bases.append(self.__class__) # don't forget me!!
+        # first let's look for old-skool versioned's
+        if "persistenceVersion" in self.__dict__:
+
+            # Hacky heuristic: if more than one class subclasses Versioned,
+            # we'll assume that the higher version number wins for the older
+            # class, so we'll consider the attribute the version of the older
+            # class.  There are obviously possibly times when this will
+            # eventually be an incorrect assumption, but hopefully old-school
+            # persistenceVersion stuff won't make it that far into multiple
+            # classes inheriting from Versioned.
+
+            pver = self.__dict__['persistenceVersion']
+            del self.__dict__['persistenceVersion']
+            highestVersion = 0
+            highestBase = None
+            for base in bases:
+                if not base.__dict__.has_key('persistenceVersion'):
+                    continue
+                if base.persistenceVersion > highestVersion:
+                    highestBase = base
+                    highestVersion = base.persistenceVersion
+            if highestBase:
+                self.__dict__['%s.persistenceVersion' % reflect.qual(highestBase)] = pver
+        for base in bases:
+            # ugly hack, but it's what the user expects, really
+            if (Versioned not in base.__bases__ and
+                'persistenceVersion' not in base.__dict__):
+                continue
+            currentVers = base.persistenceVersion
+            pverName = '%s.persistenceVersion' % reflect.qual(base)
+            persistVers = (self.__dict__.get(pverName) or 0)
+            if persistVers:
+                del self.__dict__[pverName]
+            assert persistVers <=  currentVers, "Sorry, can't go backwards in time."
+            while persistVers < currentVers:
+                persistVers = persistVers + 1
+                method = base.__dict__.get('upgradeToVersion%s' % persistVers, None)
+                if method:
+                    log.msg( "Upgrading %s (of %s @ %s) to version %s" % (reflect.qual(base), reflect.qual(self.__class__), id(self), persistVers) )
+                    method(self)
+                else:
+                    log.msg( 'Warning: cannot upgrade %s to version %s' % (base, persistVers) )