projects / OpenSPARC-T2-SAM / blame
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| 54 | <H1><A NAME="SECTION0019200000000000000000"> | |
| 55 | 17.2 <tt class="module">Bastion</tt> -- | |
| 56 | Restricting access to objects</A> | |
| 57 | </H1> | |
| 58 | ||
| 59 | <P> | |
| 60 | <A NAME="module-Bastion"></A> | |
| 61 | ||
| 62 | <span class="versionnote">Changed in version 2.3: | |
| 63 | Disabled module.</span> | |
| 64 | ||
| 65 | <P> | |
| 66 | <div class="warning"><b class="label">Warning:</b> | |
| 67 | ||
| 68 | The documentation has been left in place to help in reading old code | |
| 69 | that uses the module. | |
| 70 | </div> | |
| 71 | ||
| 72 | <P> | |
| 73 | According to the dictionary, a bastion is ``a fortified area or | |
| 74 | position'', or ``something that is considered a stronghold.'' It's a | |
| 75 | suitable name for this module, which provides a way to forbid access | |
| 76 | to certain attributes of an object. It must always be used with the | |
| 77 | <tt class="module"><a href="module-rexec.html">rexec</a></tt> module, in order to allow restricted-mode programs | |
| 78 | access to certain safe attributes of an object, while denying access | |
| 79 | to other, unsafe attributes. | |
| 80 | ||
| 81 | <P> | |
| 82 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 83 | <td><nobr><b><tt id='l2h-4934' xml:id='l2h-4934' class="function">Bastion</tt></b>(</nobr></td> | |
| 84 | <td><var>object</var><big>[</big><var>, filter</var><big>[</big><var>, | |
| 85 | name</var><big>[</big><var>, class</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> | |
| 86 | <dd> | |
| 87 | Protect the object <var>object</var>, returning a bastion for the | |
| 88 | object. Any attempt to access one of the object's attributes will | |
| 89 | have to be approved by the <var>filter</var> function; if the access is | |
| 90 | denied an <tt class="exception">AttributeError</tt> exception will be raised. | |
| 91 | ||
| 92 | <P> | |
| 93 | If present, <var>filter</var> must be a function that accepts a string | |
| 94 | containing an attribute name, and returns true if access to that | |
| 95 | attribute will be permitted; if <var>filter</var> returns false, the access | |
| 96 | is denied. The default filter denies access to any function beginning | |
| 97 | with an underscore ("<tt class="character">_</tt>"). The bastion's string representation | |
| 98 | will be "<tt class="samp"><Bastion for <var>name</var>></tt>" if a value for | |
| 99 | <var>name</var> is provided; otherwise, "<tt class="samp">repr(<var>object</var>)</tt>" will be | |
| 100 | used. | |
| 101 | ||
| 102 | <P> | |
| 103 | <var>class</var>, if present, should be a subclass of <tt class="class">BastionClass</tt>; | |
| 104 | see the code in <span class="file">bastion.py</span> for the details. Overriding the | |
| 105 | default <tt class="class">BastionClass</tt> will rarely be required. | |
| 106 | </dl> | |
| 107 | ||
| 108 | <P> | |
| 109 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 110 | <td><nobr><b><span class="typelabel">class</span> <tt id='l2h-4935' xml:id='l2h-4935' class="class">BastionClass</tt></b>(</nobr></td> | |
| 111 | <td><var>getfunc, name</var>)</td></tr></table></dt> | |
| 112 | <dd> | |
| 113 | Class which actually implements bastion objects. This is the default | |
| 114 | class used by <tt class="function">Bastion()</tt>. The <var>getfunc</var> parameter is a | |
| 115 | function which returns the value of an attribute which should be | |
| 116 | exposed to the restricted execution environment when called with the | |
| 117 | name of the attribute as the only parameter. <var>name</var> is used to | |
| 118 | construct the <tt class="function">repr()</tt> of the <tt class="class">BastionClass</tt> instance. | |
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