Package twisted :: Package spread :: Module newjelly
[show private | hide private]
[frames | no frames]

Module twisted.spread.newjelly

S-expression-based persistence of python objects.

Stability: semi-stable

Future Plans: Optimization. Lots of optimization. No semantic breakages should be necessary, but if small tweaks are required to gain acceptable large-scale performance then they will be made. Although Glyph is the maintainer, Bruce Mitchener will be supervising most of the optimization work here.

I do something very much like Pickle; however, pickle's main goal seems to be efficiency (both in space and time); jelly's main goals are security, human readability, and portability to other environments.

This is how Jelly converts various objects to s-expressions:

Boolean: True --> ['boolean', 'true']

Integer: 1 --> 1

List: [1, 2] --> ['list', 1, 2]

String: "hello" --> "hello"

Float: 2.3 --> 2.3

Dictionary: {'a' : 1, 'b' : 'c'} --> ['dictionary', ['b', 'c'], ['a', 1]]

Module: UserString --> ['module', 'UserString']

Class: UserString.UserString --> ['class', ['module', 'UserString'], 'UserString']

Function: string.join --> ['function', 'join', ['module', 'string']]

Instance: s is an instance of UserString.UserString, with a __dict__ {'data': 'hello'}: ["UserString.UserString", ['dictionary', ['data', 'hello']]]

# ['instance', ['class', ['module', 'UserString'], 'UserString'], ['dictionary', ['data', 'hello']]]

Class Method: UserString.UserString.center: ['method', 'center', ['None'], ['class', ['module', 'UserString'], 'UserString']]

Instance Method: s.center, where s is an instance of UserString.UserString: ['method', 'center', ['instance', ['reference', 1, ['class', ['module', 'UserString'], 'UserString']], ['dictionary', ['data', 'd']]], ['dereference', 1]]

Author: Glyph Lefkowitz

Classes
DummySecurityOptions DummySecurityOptions() -> insecure security options Dummy security options -- this class will allow anything.
Jellyable Inherit from me to Jelly yourself directly.
SecurityOptions This will by default disallow everything, except for 'none'.
Unjellyable Inherit from me to Unjelly yourself directly.
Unpersistable This is an instance of a class that comes back when something couldn't be persisted.
_Dummy (Internal) Dummy class, used for unserializing instances.
_Jellier (Internal) This class manages state for a call to jelly()
_Unjellier  

Exceptions
InsecureJelly This exception will be raised when a jelly is deemed `insecure'; e.g.
NullReference This object is a marker for when a reference is made to an object that can't be referenced, i.e.

Function Summary
  getInstanceState(inst, jellier)
Utility method to default to 'normal' state rules in serialization.
  jelly(object, taster, persistentStore, invoker)
Serialize to s-expression.
  setInstanceState(inst, unjellier, jellyList)
Utility method to default to 'normal' state rules in unserialization.
  setUnjellyableFactoryForClass(classname, copyFactory)
Set the factory to construct a remote instance of a type:
  setUnjellyableForClass(classname, unjellyable)
Set which local class will represent a remote type.
  setUnjellyableForClassTree(module, baseClass, prefix)
Set all classes in a module derived from baseClassas copiers for a corresponding remote class.
  unjelly(sexp, taster, persistentLoad, invoker)
Unserialize from s-expression.
  _maybeClass(classnamep)

Variable Summary
str __version__
NoneType BooleanType
str class_atom
list debugCrap
str dereference_atom
str dictionary_atom
tuple DictTypes
str function_atom
SecurityOptions globalSecurity
str list_atom
str module_atom
str None_atom
str persistent_atom
str reference_atom
str tuple_atom
dict unjellyableFactoryRegistry
dict unjellyableRegistry
str unpersistable_atom
NullReference _theNullRef

Function Details

getInstanceState(inst, jellier)

Utility method to default to 'normal' state rules in serialization.

jelly(object, taster=<twisted.spread.newjelly.DummySecurityOptions ins..., persistentStore=None, invoker=None)

Serialize to s-expression.

Returns a list which is the serialized representation of an object. An optional 'taster' argument takes a SecurityOptions and will mark any insecure objects as unpersistable rather than serializing them.

setInstanceState(inst, unjellier, jellyList)

Utility method to default to 'normal' state rules in unserialization.

setUnjellyableFactoryForClass(classname, copyFactory)

Set the factory to construct a remote instance of a type:
   jellier.setFactoryForClass('module.package.Class', MyFactory)

Call this at the module level immediately after its class definition. copyFactory should return an instance or subclass of RemoteCopy.

Similar to setUnjellyableForClass except it uses a factory instead of creating an instance.

setUnjellyableForClass(classname, unjellyable)

Set which local class will represent a remote type.

If you have written a Copyable class that you expect your client to be receiving, write a local "copy" class to represent it, then call:
   jellier.setUnjellyableForClass('module.package.Class', MyJellier).

Call this at the module level immediately after its class definition. MyCopier should be a subclass of RemoteCopy.

The classname may be a special tag returned by 'Copyable.getTypeToCopyFor' rather than an actual classname.

This call is also for cached classes, since there will be no overlap. The rules are the same.

setUnjellyableForClassTree(module, baseClass, prefix=None)

Set all classes in a module derived from baseClass as copiers for a corresponding remote class.

When you have a heirarchy of Copyable (or Cacheable) classes on one side, and a mirror structure of Copied (or RemoteCache) classes on the other, use this to setCopierForClass all your Copieds for the Copyables.

Each copyTag (the "classname" argument to getTypeToCopyFor, and what the Copyable's getTypeToCopyFor returns) is formed from adding a prefix to the Copied's class name. The prefix defaults to module.__name__. If you wish the copy tag to consist of solely the classname, pass the empty string ''.
Parameters:
module - a module object from which to pull the Copied classes. (passing sys.modules[__name__] might be useful)
baseClass - the base class from which all your Copied classes derive.
prefix - the string prefixed to classnames to form the unjellyableRegistry.

unjelly(sexp, taster=<twisted.spread.newjelly.DummySecurityOptions ins..., persistentLoad=None, invoker=None)

Unserialize from s-expression.

Takes an list that was the result from a call to jelly() and unserializes an arbitrary object from it. The optional 'taster' argument, an instance of SecurityOptions, will cause an InsecureJelly exception to be raised if a disallowed type, module, or class attempted to unserialize.

Variable Details

__version__

Type:
str
Value:
'1.9'                                                                  

BooleanType

Type:
NoneType
Value:
None                                                                   

class_atom

Type:
str
Value:
'class'                                                                

debugCrap

Type:
list
Value:
[]                                                                     

dereference_atom

Type:
str
Value:
'dereference'                                                          

dictionary_atom

Type:
str
Value:
'dictionary'                                                           

DictTypes

Type:
tuple
Value:
(<type 'dict'>,)                                                       

function_atom

Type:
str
Value:
'function'                                                             

globalSecurity

Type:
SecurityOptions
Value:
<twisted.spread.newjelly.SecurityOptions instance at 0x897f914>        

list_atom

Type:
str
Value:
'list'                                                                 

module_atom

Type:
str
Value:
'module'                                                               

None_atom

Type:
str
Value:
'None'                                                                 

persistent_atom

Type:
str
Value:
'persistent'                                                           

reference_atom

Type:
str
Value:
'reference'                                                            

tuple_atom

Type:
str
Value:
'tuple'                                                                

unjellyableFactoryRegistry

Type:
dict
Value:
{}                                                                     

unjellyableRegistry

Type:
dict
Value:
{}                                                                     

unpersistable_atom

Type:
str
Value:
'unpersistable'                                                        

_theNullRef

Type:
NullReference
Value:
<twisted.spread.newjelly.NullReference instance at 0x899287c>          

Generated by Epydoc 1.1 on Fri Jun 27 03:48:55 2003 http://epydoc.sf.net