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//usr/lib/python2.4/Bastion.pyc
mς =5Dc @ sl d Z d d g Z d k l Z d f d YZ d d e d Z d Z e d j o e n d S( sΤ Bastionification utility. A bastion (for another object -- the 'original') is an object that has the same methods as the original but does not give access to its instance variables. Bastions have a number of uses, but the most obvious one is to provide code executing in restricted mode with a safe interface to an object implemented in unrestricted mode. The bastionification routine has an optional second argument which is a filter function. Only those methods for which the filter method (called with the method name as argument) returns true are accessible. The default filter method returns true unless the method name begins with an underscore. There are a number of possible implementations of bastions. We use a 'lazy' approach where the bastion's __getattr__() discipline does all the work for a particular method the first time it is used. This is usually fastest, especially if the user doesn't call all available methods. The retrieved methods are stored as instance variables of the bastion, so the overhead is only occurred on the first use of each method. Detail: the bastion class has a __repr__() discipline which includes the repr() of the original object. This is precomputed when the bastion is created. t BastionClasst Bastion( s MethodTypec B s) t Z d Z d Z d Z d Z RS( s Helper class used by the Bastion() function. You could subclass this and pass the subclass as the bastionclass argument to the Bastion() function, as long as the constructor has the same signature (a get() function and a name for the object). c C s | | _ | | _ d S( sΧ Constructor. Arguments: get - a function that gets the attribute value (by name) name - a human-readable name for the original object (suggestion: use repr(object)) N( t gett selft _get_t namet _name_( R R R ( ( t /usr/lib/python2.4/Bastion.pyt __init__, s c C s d | i S( sΥ Return a representation string. This includes the name passed in to the constructor, so that if you print the bastion during debugging, at least you have some idea of what it is. s <Bastion for %s>N( R R ( R ( ( R t __repr__9 s c C s | i | } | | i | <| S( s Get an as-yet undefined attribute value. This calls the get() function that was passed to the constructor. The result is stored as an instance variable so that the next time the same attribute is requested, __getattr__() won't be invoked. If the get() function raises an exception, this is simply passed on -- exceptions are not cached. N( R R R t attributet __dict__( R R R ( ( R t __getattr__C s ( t __name__t __module__t __doc__R R R ( ( ( R R " s c C s | d d j S( Ni t _( R ( R ( ( R t <lambda>T s c C sN t d | | d } | d } | d j o t | } n | | | S( s· Create a bastion for an object, using an optional filter. See the Bastion module's documentation for background. Arguments: object - the original object filter - a predicate that decides whether a function name is OK; by default all names are OK that don't start with '_' name - the name of the object; default repr(object) bastionclass - class used to create the bastion; default BastionClass s- This code is not secure in Python 2.2 and 2.3c C sH | | o. t | | } t | t j o | Sq; n t | d S( s6 Internal function for Bastion(). See source comments.N( t filterR t getattrt objectR t typet MethodTypet AttributeError( R R R R ( ( R t get1r s c C s | | S( s6 Internal function for Bastion(). See source comments.N( R R ( R R ( ( R t get2z s N( t RuntimeErrorR R R R R t Nonet reprt bastionclass( R R R R R R ( ( R R T s c B s d f d Y} | } e | } d } | d Ud d Gd Gd d GHd k } | i } | i d } | | _ | i | d S( s Test the Bastion() function.t Originalc B s, t Z d Z d Z d Z d Z RS( Nc C s d | _ d S( Ni ( R t sum( R ( ( R R s c C s | i | d S( N( R t _addt n( R R! ( ( R t add s c C s | i | | _ d S( N( R R R! ( R R! ( ( R R s c C s | i S( N( R R ( R ( ( R t total s ( R R R R" R R# ( ( ( R R s sά if 1: b.add(81) b.add(18) print "b.total() =", b.total() try: print "b.sum =", b.sum, except: print "inaccessible" else: print "accessible" try: print "b._add =", b._add, except: print "inaccessible" else: print "accessible" try: print "b._get_.func_defaults =", map(type, b._get_.func_defaults), except: print "inaccessible" else: print "accessible" Nt =i s Using rexec:t __main__( R t oR t bt testcodet rexect RExect rt add_modulet mt r_exec( R' R( R- R& R) R+ R ( ( R t _test s R% N( R t __all__t typesR R R R R/ R ( R0 R/ R R R ( ( R t ? s 2/ -