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52 lines
2.3 KiB
TeX
52 lines
2.3 KiB
TeX
\section{\module{Bastion} ---
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Providing restricted access to objects.}
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\declaremodule{standard}{Bastion}
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\modulesynopsis{Providing restricted access to objects.}
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% I'm concerned that the word 'bastion' won't be understood by people
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% for whom English is a second language, making the module name
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% somewhat mysterious. Thus, the brief definition... --amk
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According to the dictionary, a bastion is ``a fortified area or
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position'', or ``something that is considered a stronghold.'' It's a
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suitable name for this module, which provides a way to forbid access
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to certain attributes of an object. It must always be used with the
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\module{rexec} module, in order to allow restricted-mode programs access
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to certain safe attributes of an object, while denying access to
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other, unsafe attributes.
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% I've punted on the issue of documenting keyword arguments for now.
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\begin{funcdesc}{Bastion}{object\optional{, filter\optional{,
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name\optional{, class}}}}
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Protect the object \var{object}, returning a bastion for the
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object. Any attempt to access one of the object's attributes will
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have to be approved by the \var{filter} function; if the access is
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denied an \exception{AttributeError} exception will be raised.
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If present, \var{filter} must be a function that accepts a string
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containing an attribute name, and returns true if access to that
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attribute will be permitted; if \var{filter} returns false, the access
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is denied. The default filter denies access to any function beginning
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with an underscore (\samp{_}). The bastion's string representation
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will be \samp{<Bastion for \var{name}>} if a value for
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\var{name} is provided; otherwise, \samp{repr(\var{object})} will be
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used.
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\var{class}, if present, should be a subclass of \class{BastionClass};
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see the code in \file{bastion.py} for the details. Overriding the
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default \class{BastionClass} will rarely be required.
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\end{funcdesc}
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\begin{classdesc}{BastionClass}{getfunc, name}
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Class which actually implements bastion objects. This is the default
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class used by \function{Bastion()}. The \var{getfunc} parameter is a
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function which returns the value of an attribute which should be
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exposed to the restricted execution environment when called with the
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name of the attribute as the only parameter. \var{name} is used to
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construct the \function{repr()} of the \class{BastionClass} instance.
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\end{classdesc}
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