pluginmgr(3tcl) Plugin management pluginmgr(3tcl)______________________________________________________________________________NAMEpluginmgr - Manage a plugin
SYNOPSIS
package require Tcl 8.4
package require pluginmgr ?0.3?
::pluginmgr objectName ?option value...?
::pluginmgr::paths objectName name...
objectName method ?arg arg ...?
objectName clone
objectName configure
objectName configure option
objectName configure -option value...
objectName cget -option
objectName destroy
objectName do arg...
objectName interpreter
objectName plugin
objectName load string
objectName unload
objectName list
objectName path path
objectName paths
_________________________________________________________________DESCRIPTION
This package provides commands and objects for the generic management
of plugins which can be loaded into an application.
To avoid the implementation of yet another system to locate Tcl code
the system provides by this package is built on top of the regular
package management system. Each plugin is considered as a package and a
simple invokation of package require is enough to locate and load it,
if it exists. The only time we will need additional paths is when a
plugin manager is part of a wrapped application and has to be able to
search for plugins existing outside of that application. For this situ‐
ation the package provides a command to create a general set of such
paths based on names for the plugin manager and/or application in ques‐
tion.
The main contribution of this package is a generic framework which
allows the easy declaration of
[1] How to translate a plugin name to the name of the package imple‐
menting it, and vice versa.
[2] The list of commands a plugin has to provide as API, and also of
more complex checks as code.
[3] The list of commands expected by the plugin from the environ‐
ment.
This then allows the easy generation of plugin managers customized to
particular types of plugins for an application.
It should be noted that all plugin code is considered untrusted and
will always be executed within a safe interpreter. The interpreter is
enabled enough to allow plugins the loading of all additional packages
they may need.
PUBLIC API
PACKAGE COMMANDS
::pluginmgr objectName ?option value...?
This command creates a new plugin manager object with an associ‐
ated Tcl command whose name is objectName. This object command
is explained in full detail in the sections OBJECT COMMAND and
OBJECT METHODS. The object command will be created under the
current namespace if the objectName is not fully qualified, and
in the specified namespace otherwise.
The options and their values coming after the name of the object
are used to set the initial configuration of the mamager object,
specifying the applicable plugins and their API.
::pluginmgr::paths objectName name...
This utility command adds a set of paths to the specified
object, based on the given names. It will search for:
[1] The environment variable name_PLUGINS. Its contents will
be interpreted as a list of package paths. The entries
have to be separated by either : (unix) or ; (windows).
The name will be converted to upper-case letters.
[2] The registry entry "HKEY_LOCAL_MACHINE\SOFT‐
WARE\name\PLUGINS". Its contents will be interpreted as
a list of package paths. The entries have to be separated
by ;. This item is considered only when on Windows (tm).
The casing of letters is not changed.
[3] The registry entry "HKEY_CURRENT_USER\SOFTWARE\name\PLUG‐
INS". Its contents will be interpreted as a list of
package paths. The entries have to be separated by ;.
This item is considered only when on Windows (tm).
The casing of letters is not changed.
[4] The directory "~/.name/plugin".
[5] The directory "~/.name/plugins".
The casing of letters is not changed.
and add all the paths found that way to the list of package paths main‐
tained by the object.
If name is namespaced each item in the list will be repeated per prefix
of name, with conversion of :-sequences into the proper separator
(underscore for environment variables, backslash for registry entries,
and / for directories).
Examples:
::pluginmgr::paths ::obj docidx
=> env DOCIDX_PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\docidx\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\docidx\PLUGINS
path ~/.docidx/plugins
::pluginmgr::paths ::obj doctools::idx
=> env DOCTOOLS_PLUGINS
env DOCTOOLS_IDX_PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\doctools\PLUGINS
reg HKEY_LOCAL_MACHINE\SOFTWARE\doctools\idx\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\doctools\PLUGINS
reg HKEY_CURRENT_USER\SOFTWARE\doctools\idx\PLUGINS
path ~/.doctools/plugin
path ~/.doctools/idx/plugin
OBJECT COMMAND
All commands created by the command ::pluginmgr (See section PACKAGE
COMMANDS) have the following general form and may be used to invoke
various operations on their plugin manager object.
objectName method ?arg arg ...?
The method method and its arg'uments determine the exact behav‐
ior of the command. See section OBJECT METHODS for the detailed
specifications.
OBJECT METHODS
objectName clone
This method creates a new plugin management object and returns
the associated object command. The generated object is a clone
of the object the method was invoked on. I.e. the new object
will have the same configuration as the current object. With
regard to state, if the current object has a plugin loaded then
this plugin and all associated state is moved to the generated
clone and the current object is reset into the base state (no
plugin loaded). In this manner a configured plugin manager is
also a factory for loaded plugins.
objectName configure
The method returns a list of all known options and their current
values when called without any arguments.
objectName configure option
The method behaves like the method cget when called with a sin‐
gle argument and returns the value of the option specified by
said argument.
objectName configure -option value...
The method reconfigures the specified options of the object,
setting them to the associated values, when called with an even
number of arguments, at least two.
The legal options are described in the section OBJECT CONFIGURA‐
TION.
objectName cget -option
This method expects a legal configuration option as argument and
will return the current value of that option for the object the
method was invoked for.
The legal configuration options are described in section OBJECT
CONFIGURATION.
objectName destroy
This method destroys the object it is invoked for.
objectName do arg...
This method interprets its list of arguments as the words of a
command and invokes this command in the execution context of the
plugin. The result of the invoked command is made the result of
the method. The call will fail with an error if no valid plugin
has been loaded into the manager object.
objectName interpreter
This method returns the handle of the safe interpreter the cur‐
rent plugin is loaded into. An empty string as return value sig‐
nals that the manager currently has no valid plugin loaded.
objectName plugin
This method returns the name of the plugin currently loaded. An
empty string as return value signals that the manager currently
has no valid plugin loaded.
objectName load string
This method loads, validates, and initializes a named plugin
into the manager object.
The algorithm to locate and load the plugin employed is:
[1] If the string contains the path to an existing file then
this file is taken as the implementation of the plugin.
[2] Otherwise the plugin name is translated into a package
name via the value of the option -pattern and then loaded
through the regular package management.
[3] The load fails.
The algorithm to validate and initialize the loaded code is:
[1] If the option -api is non-empty introspection commands
are used to ascertain that the plugin provides the listed
commands.
[2] If the option -check is non-empty the specified command
prefix is called.
[3] If either of the above fails the candidate plugin is
unloaded again
[4] Otherwise all the commands specified via the option -cmds
are installed in the plugin.
A previously loaded plugin is discarded, but only if the new plugin was
found and sucessfully validated and initialized. Note that there will
be no intereference between old and new plugin as both will be put into
separate safe interpreters.
objectName unload
This method unloads the currently loaded plugin. It returns the
empty string. The call will be silently ignored if no plugin is
loaded at all.
objectName list
This method uses the contents of the option -pattern to find all
packages which can be plugins under the purview of this manager
object. It translates their names into plugin names and returns
a list containing them.
objectName path path
This methods adds the specified path to the list of additional
package paths to look at when searching for a plugin. It returns
the empty string. Duplicate paths are ignored, i.e. each path is
added only once. Paths are made absolute, but are not normal‐
ized.
objectName paths
This method returns a list containing all additional paths which
have been added to the plugin manager object since its creation.
OBJECT CONFIGURATION
All plugin manager objects understand the following configuration
options:
-pattern string
The value of this option is a glob pattern which has to contain
exactly one '*'-operator. All packages whose names match this
pattern are the plugins recognized by the manager object. And
vice versa, the replacement of the '*'-operator with a plugin
name will yield the name of the package implementing that plug‐
in.
This option has no default, except if option -name was set. It
has to be set before attempting to load a plugin, either
directly, or through option -name.
-api list
The value of this option is a list of command names, and any
plugin loaded has to provide these commands. Names which are not
fully qualified are considered to be rooted in the global names‐
pace. If empty no expectations are made on the plugin. The
default value is the empty list.
-check cmdprefix
The value of this option is interpreted as a command prefix.
Its purpose is to perform complex checks on a loaded plugin
package to validate it, which go beyond a simple list of pro‐
vided commands.
It is called with the manager object command as the only argu‐
ment and has to return a boolean value. A value of true will be
interpreted to mean that the candidate plugin passed the test.
The call will happen if and only if the candidate plugin already
passed the basic API check specified through the option -api.
The default value is the empty list, which causes the manager
object to suppress the call and to assume the candidate plugin
passes.
-cmds dict
The value of this option is a dictionary. It specifies the com‐
mands which will be made available to the plugin (as keys), and
the trusted commands in the environment which implement them (as
values). The trusted commands will be executed in the inter‐
preter specified by the option -cmdip. The default value is the
empty dictionary.
-cmdip ipspec
The value of this option is the path of the interpreter where
the trusted commands given to the plugin will be executed in.
The default is the empty string, referring to the current inter‐
preter.
-setup cmdprefix
The value of this option is interpreted as a command prefix.
It is called whenever a new safe interpreter for a plugin has
been created, but before a plugin is loaded. It is provided with
the manager object command and the interpreter handle as its
only arguments. Any return value will be ignored.
Its purpose is give a user of the plugin management the ability
to define commands, packages, etc. a chosen plugin may need
while being loaded.
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain
bugs and other problems. Please report such in the category pluginmgr
of the Tcllib SF Trackers [http://source‐
forge.net/tracker/?group_id=12883]. Please also report any ideas for
enhancements you may have for either package and/or documentation.
KEYWORDS
plugin management, plugin search
CATEGORY
Programming tools
COPYRIGHT
Copyright (c) 2005 Andreas Kupries <andreas_kupries@users.sourceforge.net>
pluginmgr 0.3 pluginmgr(3tcl)
