This class allows loading and unloading of dynamically linked libraries which contain class definitions from which objects can be created/destroyed during runtime (i.e. class_loader). Libraries loaded by a ClassLoader are only accessible within scope of that ClassLoader object. More...

#include <class_loader.hpp>

Public Member Functions
	ClassLoader (const std::string &library_path, bool ondemand_load_unload=false)
	Constructor for ClassLoader.
template<class Base >
boost::shared_ptr< Base >	createInstance (const std::string &derived_class_name)
	Generates an instance of loadable classes (i.e. class_loader).
template<class Base >
Base *	createUnmanagedInstance (const std::string &derived_class_name)
	Generates an instance of loadable classes (i.e. class_loader).
template<class Base >
std::vector< std::string >	getAvailableClasses ()
	Indicates which classes (i.e. class_loader) that can be loaded by this object.
std::string	getLibraryPath ()
	Gets the full-qualified path and name of the library associated with this class loader.
template<class Base >
bool	isClassAvailable (const std::string &class_name)
	Indicates if a plugin class is available.
bool	isLibraryLoaded ()
	Indicates if a library is loaded within the scope of this ClassLoader. Note that the library may already be loaded internally through another ClassLoader, but until loadLibrary() method is called, the ClassLoader cannot create objects from said library. If we want to see if the library has been opened by somebody else,.
bool	isLibraryLoadedByAnyClassloader ()
	Indicates if a library is loaded by some entity in the plugin system (another ClassLoader), but not necessarily loaded by this ClassLoader.
bool	isOnDemandLoadUnloadEnabled ()
	Indicates if the library is to be loaded/unloaded on demand...meaning that only to load a lib when the first plugin is created and automatically shut it down when last active plugin is destroyed.
void	loadLibrary ()
	Attempts to load a library on behalf of the ClassLoader. If the library is already opened, this method has no effect. If the library has been already opened by some other entity (i.e. another ClassLoader or global interface), this object is given permissions to access any plugin classes loaded by that other entity. This is.
int	unloadLibrary ()
	Attempts to unload a library loaded within scope of the ClassLoader. If the library is not opened, this method has no effect. If the library is opened by other another ClassLoader, the library will NOT be unloaded internally -- however this ClassLoader will no longer be able to instantiate class_loader bound to that library. If there are plugin objects that exist in memory created by this classloader, a warning message will appear and the library will not be unloaded. If loadLibrary() was called multiple times (e.g. in the case of multiple threads or purposefully in a single thread), the user is responsible for calling unloadLibrary() the same number of times. The library will not be unloaded within the context of this classloader until the number of unload calls matches the number of loads.
virtual	~ClassLoader ()
	Destructor for ClassLoader. All libraries opened by this ClassLoader are unloaded automatically.
Private Member Functions
template<class Base >
Base *	createRawInstance (const std::string &derived_class_name, bool managed)
	Generates an instance of loadable classes (i.e. class_loader).
template<class Base >
void	onPluginDeletion (Base *obj)
	Callback method when a plugin created by this class loader is destroyed.
int	unloadLibraryInternal (bool lock_plugin_ref_count)
	As the library may be unloaded in "on-demand load/unload" mode, unload maybe called from createInstance(). The problem is that createInstance() locks the plugin_ref_count as does unloadLibrary(). This method is the implementation of unloadLibrary but with a parameter to decide if plugin_ref_mutex_ should be locked.
Static Private Member Functions
static bool	hasUnmanagedInstanceBeenCreated ()
	Getter for if an unmanaged (i.e. unsafe) instance has been created flag.
Private Attributes
std::string	library_path_
int	load_ref_count_
boost::recursive_mutex	load_ref_count_mutex_
bool	ondemand_load_unload_
int	plugin_ref_count_
boost::recursive_mutex	plugin_ref_count_mutex_
Static Private Attributes
static bool	has_unmananged_instance_been_created_ = false

Detailed Description

This class allows loading and unloading of dynamically linked libraries which contain class definitions from which objects can be created/destroyed during runtime (i.e. class_loader). Libraries loaded by a ClassLoader are only accessible within scope of that ClassLoader object.

A base class for all class_loader exceptions that inherits from std::runtime_exception.

Definition at line 66 of file class_loader.hpp.

Constructor & Destructor Documentation

class_loader::ClassLoader::ClassLoader	(	const std::string &	library_path,
		bool	ondemand_load_unload = `false`
	)

Constructor for ClassLoader.

Parameters:

library_path	- The path of the runtime library to load
ondemand_load_unload	- Indicates if on-demand (lazy) unloading/loading of libraries occurs as plugins are created/destroyed

Definition at line 49 of file class_loader.cpp.

class_loader::ClassLoader::~ClassLoader ( ) [virtual]

Destructor for ClassLoader. All libraries opened by this ClassLoader are unloaded automatically.

Definition at line 64 of file class_loader.cpp.

Member Function Documentation

template<class Base >

boost::shared_ptr<Base> class_loader::ClassLoader::createInstance ( const std::string & derived_class_name ) [inline]

Generates an instance of loadable classes (i.e. class_loader).

It is not necessary for the user to call loadLibrary() as it will be invoked automatically if the library is not yet loaded (which typically happens when in "On Demand Load/Unload" mode).

Parameters:

derived_class_name The name of the class we want to create (

See also:: getAvailableClasses())

Returns:: A boost::shared_ptr<Base> to newly created plugin object

Definition at line 114 of file class_loader.hpp.

template<class Base >

Base* class_loader::ClassLoader::createRawInstance	(	const std::string &	derived_class_name,
		bool	managed
	)		`[inline, private]`

Generates an instance of loadable classes (i.e. class_loader).

It is not necessary for the user to call loadLibrary() as it will be invoked automatically if the library is not yet loaded (which typically happens when in "On Demand Load/Unload" mode).

Parameters:

derived_class_name The name of the class we want to create (

See also:: getAvailableClasses())

Parameters:

managed If true, the returned pointer is assumed to be wrapped in a smart pointer by the caller.

Returns:: A Base* to newly created plugin object

Definition at line 247 of file class_loader.hpp.

template<class Base >

Base* class_loader::ClassLoader::createUnmanagedInstance ( const std::string & derived_class_name ) [inline]

Generates an instance of loadable classes (i.e. class_loader).

It is not necessary for the user to call loadLibrary() as it will be invoked automatically if the library is not yet loaded (which typically happens when in "On Demand Load/Unload" mode).

Creating an unmanaged instance disables dynamically unloading libraries when managed pointers go out of scope for all class loaders in this process.

Parameters:

derived_class_name The name of the class we want to create (

See also:: getAvailableClasses())

Returns:: An unmanaged (i.e. not a shared_ptr) Base* to newly created plugin object.

Definition at line 157 of file class_loader.hpp.

template<class Base >

std::vector<std::string> class_loader::ClassLoader::getAvailableClasses ( ) [inline]

Indicates which classes (i.e. class_loader) that can be loaded by this object.

Returns:: vector of strings indicating names of instantiable classes derived from <Base>

Definition at line 94 of file class_loader.hpp.

std::string class_loader::ClassLoader::getLibraryPath ( ) [inline]

Gets the full-qualified path and name of the library associated with this class loader.

Definition at line 102 of file class_loader.hpp.

bool class_loader::ClassLoader::hasUnmanagedInstanceBeenCreated ( ) [static, private]

Getter for if an unmanaged (i.e. unsafe) instance has been created flag.

Definition at line 39 of file class_loader.cpp.

template<class Base >

bool class_loader::ClassLoader::isClassAvailable ( const std::string & class_name ) [inline]

Indicates if a plugin class is available.

Parameters:

Base	- polymorphic type indicating base class
class_name	- the name of the plugin class

Returns:: true if yes it is available, false otherwise

Definition at line 169 of file class_loader.hpp.

bool class_loader::ClassLoader::isLibraryLoaded ( )

Indicates if a library is loaded within the scope of this ClassLoader. Note that the library may already be loaded internally through another ClassLoader, but until loadLibrary() method is called, the ClassLoader cannot create objects from said library. If we want to see if the library has been opened by somebody else,.

See also:: isLibraryLoadedByAnyClassloader()

Parameters:

library_path The path to the library to load

Returns:: true if library is loaded within this ClassLoader object's scope, otherwise false

Definition at line 72 of file class_loader.cpp.

bool class_loader::ClassLoader::isLibraryLoadedByAnyClassloader ( )

Indicates if a library is loaded by some entity in the plugin system (another ClassLoader), but not necessarily loaded by this ClassLoader.

Returns:: true if library is loaded within the scope of the plugin system, otherwise false

Definition at line 77 of file class_loader.cpp.

bool class_loader::ClassLoader::isOnDemandLoadUnloadEnabled ( ) [inline]

Indicates if the library is to be loaded/unloaded on demand...meaning that only to load a lib when the first plugin is created and automatically shut it down when last active plugin is destroyed.

Definition at line 192 of file class_loader.hpp.

void class_loader::ClassLoader::loadLibrary ( )

Attempts to load a library on behalf of the ClassLoader. If the library is already opened, this method has no effect. If the library has been already opened by some other entity (i.e. another ClassLoader or global interface), this object is given permissions to access any plugin classes loaded by that other entity. This is.

Parameters:

library_path The path to the library to load

Definition at line 82 of file class_loader.cpp.

template<class Base >

void class_loader::ClassLoader::onPluginDeletion ( Base * obj ) [inline, private]

Callback method when a plugin created by this class loader is destroyed.

Parameters:

obj	- A pointer to the deleted object

Definition at line 212 of file class_loader.hpp.

int class_loader::ClassLoader::unloadLibrary ( )

Attempts to unload a library loaded within scope of the ClassLoader. If the library is not opened, this method has no effect. If the library is opened by other another ClassLoader, the library will NOT be unloaded internally -- however this ClassLoader will no longer be able to instantiate class_loader bound to that library. If there are plugin objects that exist in memory created by this classloader, a warning message will appear and the library will not be unloaded. If loadLibrary() was called multiple times (e.g. in the case of multiple threads or purposefully in a single thread), the user is responsible for calling unloadLibrary() the same number of times. The library will not be unloaded within the context of this classloader until the number of unload calls matches the number of loads.

Returns:: The number of times more unloadLibrary() has to be called for it to be unbound from this ClassLoader

Definition at line 89 of file class_loader.cpp.

int class_loader::ClassLoader::unloadLibraryInternal ( bool lock_plugin_ref_count ) [private]

As the library may be unloaded in "on-demand load/unload" mode, unload maybe called from createInstance(). The problem is that createInstance() locks the plugin_ref_count as does unloadLibrary(). This method is the implementation of unloadLibrary but with a parameter to decide if plugin_ref_mutex_ should be locked.

Parameters:

lock_plugin_ref_count - Set to true if plugin_ref_count_mutex_ should be locked, else false