ACE_Object_Manager Class Reference

Manager for ACE library services and singleton cleanup. More...

#include <Object_Manager.h>

Inheritance diagram for ACE_Object_Manager:

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Collaboration diagram for ACE_Object_Manager:

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List of all members.

Public Types

enum  Preallocated_Object { ACE_FILECACHE_LOCK, ACE_STATIC_OBJECT_LOCK, ACE_PREALLOCATED_OBJECTS }
enum  Preallocated_Array { ACE_EMPTY_PREALLOCATED_ARRAY, ACE_PREALLOCATED_ARRAYS }

Public Member Functions

virtual int init (void)
virtual int fini (void)
 ACE_Object_Manager (void)
 ~ACE_Object_Manager (void)

Static Public Member Functions

static int starting_up (void)
static int shutting_down (void)
static int at_exit (ACE_Cleanup *object, void *param=0)
static int at_exit (void *object, ACE_CLEANUP_FUNC cleanup_hook, void *param)
static ACE_Sig_Setdefault_mask (void)
static ACE_Object_Managerinstance (void)

Static Public Attributes

static void * preallocated_object [ACE_PREALLOCATED_OBJECTS] = { 0 }
 Table of preallocated objects.
static void * preallocated_array [ACE_PREALLOCATED_ARRAYS] = { 0 }
 Table of preallocated arrays.

Private Member Functions

int at_exit_i (void *object, ACE_CLEANUP_FUNC cleanup_hook, void *param)
 ACE_Object_Manager (const ACE_Object_Manager &)
ACE_Object_Manageroperator= (const ACE_Object_Manager &)

Private Attributes

ACE_OS_Exit_Info exit_info_
 For at_exit support.
ACE_Object_Manager_Preallocationspreallocations_
 Preallocated objects collection.
ACE_Sig_Adapterace_service_config_sig_handler_
 ACE_Service_Config signal handler.

Static Private Attributes

static ACE_Object_Managerinstance_ = 0
 Singleton pointer.

Friends

class ACE_Object_Manager_Manager

Detailed Description

Manager for ACE library services and singleton cleanup.

The <ACE_Object_Manager> manages cleanup of objects, typically singletons, at program termination. In addition to managing the cleanup of the ACE library, it provides an interface for application to register objects to be cleaned up. This class also shuts down ACE library services, so that they can reclaim their storage, at program termination. It works by creating a static instance whose destructor gets called along with those of all other static objects. Hooks are provided for application code to register objects and arrays for cleanup, e.g., destruction. The order of such cleanup calls is in the reverse order of registration, i.e., that last object/array to register gets cleaned up first. The <ACE_Object_Manager> API includes <ACE_Managed_Object>. That class is contained in a separate file because it is a template class, and some compilers require that template and non-template class definitions appear in separate files. Please see ace/Managed_Object.h for a description of that part of the API. In summary, <ACE_Managed_Object> provides two adapters, the <ACE_Cleanup_Adapter> and <ACE_Managed_Object> template classes for adapting objects of any type to be easily managed by the <ACE_Object_Manager>. There are several mechanisms for adapting objects and arrays for cleanup at program termination, in roughly increasing order of ease-of-use: 1) Derive the object's class from <ACE_Cleanup>. 2) Allow the <ACE_Object_Manager> to both dynamically allocate and deallocate the object. 3) Provide an <ACE_CLEANUP_FUNC> cleanup hook for the object or array. 4) Allow the <ACE_Object_Manager> to both preallocate the object or array, either statically in global data or dynamically on the heap, when its singleton instance is construction.

There are also several mechanisms for registering objects and arrays for cleanup. In decreasing order of flexibility and complexity (with the exception of the last mechanism):

1) ACE_Object_Manager::at_exit (void *object, ACE_CLEANUP_FUNC cleanup_hook, void *param); can be used to register any object or array for any cleanup activity at program termination. 2) ACE_Object_Manager::at_exit (ACE_Cleanup *object, void *param = 0); can be used to register an <ACE_Cleanup> object for any cleanup activity at program termination. The final mechanism is not general purpose, but can only be used to allocate objects and arrays at program startup: 3) ACE_Managed_Object::get_preallocated_object (ACE_Object_Manager::Preallocated_Object id); and ACE_Managed_Object::get_preallocated_array (ACE_Object_Manager::Preallocated_Array id); can only be used to allocate objects at program startup, either in global data or on the heap (selected at compile time). These are intended to replace static locks, etc. Instead of creating a static <ACE_Object_Manager> instance, one can alternatively be created on the stack of the main program thread. It is created just after entry to main (int, char *[]), and before any existing code in that function is executed. To enable this alternative, add define ACE_HAS_NONSTATIC_OBJECT_MANAGER before including the platform specific config-* file in ace/config.h prior to building the ACE library and your applications. This define is enabled in some config files that are supplied with ACE.

To ensure a static object manager is used, undef ACE_HAS_NONSTATIC_OBJECT_MANAGER *after* including the platform specific config-* file. Note that the ACE_Object_Manager _must_ be created before any threads are spawned by the program. If ACE_HAS_NONSTATIC_OBJECT_MANAGER is not defined, the ACE library creates a static, singleton <ACE_Object_Manager> instance. The instance is placed in global program data, and constructed via a static object constructor. If ACE_HAS_NONSTATIC_OBJECT_MANAGER is defined, the <ACE_Object_Manager> instance is created on the stack of the main program thread, as noted above.

With ACE_HAS_NONSTATIC_OBJECT_MANAGER enabled, the ACE library has no static objects that require destruction. However, there are two drawbacks to using it: 1) main (int, char *[]) must be declared with arguments, even if they're not used. All of ACE is converted to this, so just applications have to be concerned with it. 2) If there any static objects that depend on those that are cleaned up by the Object_Manager, they'll get cleaned up too late. The ACE tests do not violate this requirement. However, applications may have trouble with it. NOTE on the use of <exit> -- <exit> does not destroy automatic objects. Therefore, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is enabled, the <ACE_Object_Manager> instance will *not* be destroyed if <exit> is called! However, <ACE_OS::exit> will properly destroy the ACE_Object_Manager. It is highly recommended that <ACE_OS::exit> be used instead of <exit>.

However, <exit> and <ACE_OS::exit> are tricky to use properly, especially in multithread programs. It is much safer to throw an exception (or simulate that effect) that will be caught by <main> instead of calling exit. Then, <main> can perform any necessary application-specific cleanup and return the status value. In addition, it's usually best to avoid calling <exit> and <ACE_OS::exit> from threads other than the main thread. Thanks to Jeff Greif <jmg@trivida.com> for pointing out that <exit> doesn't destroy automatic objects, and for developing the recommendations in this paragraph.

Instead of creating a static <ACE_Object_Manager>, or letting ACE create it on the stack of <main> for you, another alternative is to define ACE_DOESNT_INSTANTIATE_NONSTATIC_OBJECT_MANAGER. With that define, the application must create the ACE_Object_Manager. The recommended way is to call <ACE::init> at the start of the program, and call <ACE::fini> at the end. Alternatively, the application could explicity construct an <ACE_Object_Manager>.


Member Enumeration Documentation

enum ACE_Object_Manager::Preallocated_Array
 

Unique identifiers for preallocated arrays. Please see ace/Managed_Object.h for information on accessing preallocated arrays.

Enumerator:
ACE_EMPTY_PREALLOCATED_ARRAY  There currently are no preallocated arrays in the ACE library. If the application doesn't have any, make sure the the preallocated_array size is at least one by declaring this dummy . . .
ACE_PREALLOCATED_ARRAYS  Hook for preallocated arrays provided by application.

enum ACE_Object_Manager::Preallocated_Object
 

Unique identifiers for preallocated objects. Please see ace/Managed_Object.h for information on accessing preallocated objects.

Enumerator:
ACE_FILECACHE_LOCK 
ACE_STATIC_OBJECT_LOCK 
ACE_PREALLOCATED_OBJECTS 


Constructor & Destructor Documentation

ACE_Object_Manager::ACE_Object_Manager void   ) 
 

ACE_Object_Manager::~ACE_Object_Manager void   ) 
 

ACE_Object_Manager::ACE_Object_Manager const ACE_Object_Manager  )  [private]
 


Member Function Documentation

ACE_INLINE int ACE_Object_Manager::at_exit void *  object,
ACE_CLEANUP_FUNC  cleanup_hook,
void *  param
[static]
 

Register an object (or array) for cleanup at process termination. "cleanup_hook" points to a (global, or static member) function that is called for the object or array when it to be destroyed. It may perform any necessary cleanup specific for that object or its class. "param" is passed as the second parameter to the "cleanup_hook" function; the first parameter is the object (or array) to be destroyed. "cleanup_hook", for example, may delete the object (or array). For OS's that do not have processes, this function is the same as <at_thread_exit>. Returns 0 on success. On failure, returns -1 and sets errno to: EAGAIN if shutting down, ENOMEM if insufficient virtual memory, or EEXIST if the object (or array) had already been registered.

ACE_INLINE int ACE_Object_Manager::at_exit ACE_Cleanup object,
void *  param = 0
[static]
 

Register an ACE_Cleanup object for cleanup at process termination. The object is deleted via the <ace_cleanup_destroyer>. If you need more flexiblity, see the <other at_exit>=""> method below. For OS's that do not have processes, cleanup takes place at the end of <main>. Returns 0 on success. On failure, returns -1 and sets errno to: EAGAIN if shutting down, ENOMEM if insufficient virtual memory, or EEXIST if the object (or array) had already been registered.

int ACE_Object_Manager::at_exit_i void *  object,
ACE_CLEANUP_FUNC  cleanup_hook,
void *  param
[private]
 

Register an object or array for deletion at program termination. See description of static version above for return values.

ACE_INLINE ACE_Sig_Set & ACE_Object_Manager::default_mask void   )  [static]
 

Deprecated:
Accesses a default signal set used, for example, in ACE_Sig_Guard methods. Deprecated: use ACE_Object_Manager::default_mask () instead.

int ACE_Object_Manager::fini void   )  [virtual]
 

Explicitly destroy the singleton instance of the ACE_Object_Manager. Returns 0 on success, -1 on failure, and 1 if it had already been called.

Implements ACE_Object_Manager_Base.

int ACE_Object_Manager::init void   )  [virtual]
 

Explicitly initialize (construct the singleton instance of) the ACE_Object_Manager. Returns 0 on success, -1 on failure, and 1 if it had already been called.

Implements ACE_Object_Manager_Base.

ACE_Object_Manager * ACE_Object_Manager::instance void   )  [static]
 

Accessor to singleton instance. Because static member functions are provided in the interface, this should not be public. However, it is public so that ACE_Managed_Object<TYPE> can access it.

ACE_Object_Manager& ACE_Object_Manager::operator= const ACE_Object_Manager  )  [private]
 

int ACE_Object_Manager::shutting_down void   )  [static]
 

Returns 1 after the ACE_Object_Manager has been destroyed. This flag can be used to determine if the program is in the midst of destroying static objects. (Note that the program might destroy some static objects before this flag can return 1, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is not defined.)

int ACE_Object_Manager::starting_up void   )  [static]
 

Returns 1 before the ACE_Object_Manager has been constructed. This flag can be used to determine if the program is constructing static objects. If no static object spawns any threads, the program will be single-threaded when this flag returns 1. (Note that the program still might construct some static objects when this flag returns 0, if ACE_HAS_NONSTATIC_OBJECT_MANAGER is not defined.)


Friends And Related Function Documentation

friend class ACE_Object_Manager_Manager [friend]
 


Member Data Documentation

ACE_Sig_Adapter* ACE_Object_Manager::ace_service_config_sig_handler_ [private]
 

ACE_Service_Config signal handler.

ACE_OS_Exit_Info ACE_Object_Manager::exit_info_ [private]
 

For at_exit support.

ACE_Object_Manager * ACE_Object_Manager::instance_ = 0 [static, private]
 

Singleton pointer.

void * ACE_Object_Manager::preallocated_array = { 0 } [static]
 

Table of preallocated arrays.

void * ACE_Object_Manager::preallocated_object = { 0 } [static]
 

Table of preallocated objects.

ACE_Object_Manager_Preallocations* ACE_Object_Manager::preallocations_ [private]
 

Preallocated objects collection.


The documentation for this class was generated from the following files:
Generated on Wed Nov 23 15:49:32 2005 for ACE by  doxygen 1.4.5