ACE_SV_Semaphore_Complex Class Reference

This is a more complex semaphore wrapper that handles race conditions for initialization correctly... More...

#include <SV_Semaphore_Complex.h>

Inheritance diagram for ACE_SV_Semaphore_Complex:

Collaboration diagram for ACE_SV_Semaphore_Complex:

Public Types
enum	{ ACE_CREATE = IPC_CREAT , ACE_OPEN = 0 }

Public Member Functions
	ACE_SV_Semaphore_Complex ()
	ACE_SV_Semaphore_Complex (key_t key, short create=ACE_SV_Semaphore_Complex::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
	ACE_SV_Semaphore_Complex (const char *name, short create=ACE_SV_Semaphore_Complex::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
	~ACE_SV_Semaphore_Complex ()
int	open (const char *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
int	open (key_t key, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
int	close ()
int	acquire (u_short n=0, short flags=0) const
	Acquire the semaphore.
int	acquire_read (u_short n=0, short flags=0) const
	Acquire a semaphore for reading.
int	acquire_write (u_short n=0, short flags=0) const
	Acquire a semaphore for writing.
int	tryacquire (u_short n=0, short flags=0) const
	Try to acquire the semaphore.
int	tryacquire_read (u_short n=0, short flags=0) const
	Try to acquire the semaphore for reading.
int	tryacquire_write (u_short n=0, short flags=0) const
	Try to acquire the semaphore for writing.
int	release (u_short n=0, short flags=0) const
	Release the semaphore.
int	op (short val, u_short n=0, short flags=0) const
int	op (sembuf op_vec[], u_short n) const
int	control (int cmd, semun arg, u_short n=0) const
int	control (int cmd, int value=0, u_short n=0) const
void	dump () const
	Dump the state of an object.
int	get_id () const
	Get underlying internal id.
int	remove () const

Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks.

Static Private Attributes
static const int	BIGCOUNT_ = 10000
static sembuf	op_lock_ [2]
static sembuf	op_endcreate_ [2]
static sembuf	op_open_ [1]
static sembuf	op_close_ [3]
static sembuf	op_unlock_ [1]

Additional Inherited Members
Private Types inherited from ACE_SV_Semaphore_Simple
enum	{ ACE_CREATE = IPC_CREAT , ACE_EXCL = IPC_EXCL , ACE_OPEN = 0 }
Private Member Functions inherited from ACE_SV_Semaphore_Simple
	ACE_SV_Semaphore_Simple ()
	ACE_SV_Semaphore_Simple (key_t key, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
	ACE_SV_Semaphore_Simple (const char *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
	ACE_SV_Semaphore_Simple (const wchar_t *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
	~ACE_SV_Semaphore_Simple ()
int	open (const char *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
int	open (const wchar_t *name, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
int	open (key_t key, short flags=ACE_SV_Semaphore_Simple::ACE_CREATE, int initial_value=1, u_short nsems=1, mode_t perms=ACE_DEFAULT_FILE_PERMS)
int	close ()
int	remove () const
int	acquire (u_short n=0, short flags=0) const
int	acquire_read (u_short n=0, short flags=0) const
	Acquire a semaphore for reading.
int	acquire_write (u_short n=0, short flags=0) const
	Acquire a semaphore for writing.
int	tryacquire (u_short n=0, short flags=0) const
	Non-blocking version of <acquire>.
int	tryacquire_read (u_short n=0, short flags=0) const
	Try to acquire the semaphore for reading.
int	tryacquire_write (u_short n=0, short flags=0) const
	Try to acquire the semaphore for writing.
int	release (u_short n=0, short flags=0) const
int	op (short val, u_short semnum=0, short flags=SEM_UNDO) const
int	op (sembuf op_vec[], u_short nsems) const
	General ACE_SV_Semaphore operation on an array of SV_Semaphores.
int	control (int cmd, semun arg, u_short n=0) const
int	control (int cmd, int value=0, u_short n=0) const
int	get_id () const
	Get underlying internal id.
void	dump () const
	Dump the state of an object.
key_t	name_2_key (const char *name)
Private Attributes inherited from ACE_SV_Semaphore_Simple
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks.
key_t	key_
	Semaphore key.
int	internal_id_
	Internal ID to identify the semaphore group within this process.
int	sem_number_
	Number of semaphores we're creating.

Detailed Description

This is a more complex semaphore wrapper that handles race conditions for initialization correctly...

This code is a port to C++, inspired by: W. Richard Stevens from his book: UNIX Network Programming (Prentice Hall, ISBN 0-13-949876-1 - 1990). We provide a simpler and easier to understand interface to the System V Semaphore system calls. We create and use a 2 + n-member set for the requested ACE_SV_Semaphore_Complex. The first member, [0], is a counter used to know when all processes have finished with the ACE_SV_Semaphore_Complex. The counter is initialized to a large number, decremented on every create or open and incremented on every close. This way we can use the "adjust" feature provided by System V so that any process that exit's without calling <close> is accounted for. It doesn't help us if the last process does this (as we have no way of getting control to remove the ACE_SV_Semaphore_Complex) but it will work if any process other than the last does an exit (intentional or unintentional). The second member, [1], of the semaphore is used as a lock variable to avoid any race conditions in the create() and close() functions. The members beyond [1] are actual semaphore values in the array of semaphores, which may be sized by the user in the constructor.

Member Enumeration Documentation

anonymous enum

anonymous enum

Enumerator
ACE_CREATE
ACE_OPEN

Constructor & Destructor Documentation

ACE_SV_Semaphore_Complex() [1/3]

ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex

(

)

ACE_SV_Semaphore_Complex() [2/3]

ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex	(	key_t	key,
		short	create = ACE_SV_Semaphore_Complex::ACE_CREATE,
		int	initial_value = 1,
		u_short	nsems = 1,
		mode_t	perms = ACE_DEFAULT_FILE_PERMS )

ACE_SV_Semaphore_Complex() [3/3]

ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex	(	const char *	name,
		short	create = ACE_SV_Semaphore_Complex::ACE_CREATE,
		int	initial_value = 1,
		u_short	nsems = 1,
		mode_t	perms = ACE_DEFAULT_FILE_PERMS )

~ACE_SV_Semaphore_Complex()

ACE_SV_Semaphore_Complex::~ACE_SV_Semaphore_Complex

(

)

Member Function Documentation

acquire()

int ACE_SV_Semaphore_Complex::acquire ( u_short n = 0, short flags = 0 ) const

inline

Acquire the semaphore.

acquire_read()

int ACE_SV_Semaphore_Complex::acquire_read ( u_short n = 0, short flags = 0 ) const

inline

Acquire a semaphore for reading.

acquire_write()

int ACE_SV_Semaphore_Complex::acquire_write ( u_short n = 0, short flags = 0 ) const

inline

Acquire a semaphore for writing.

close()

int ACE_SV_Semaphore_Complex::close

(

)

Close an ACE_SV_Semaphore. Unlike the remove() method, this method is for a process to call before it exits, when it is done with the ACE_SV_Semaphore. We "decrement" the counter of processes using the ACE_SV_Semaphore, and if this was the last one, we can remove the ACE_SV_Semaphore.

control() [1/2]

int ACE_SV_Semaphore_Complex::control ( int cmd, int value = 0, u_short n = 0 ) const

inline

control() [2/2]

int ACE_SV_Semaphore_Complex::control ( int cmd, semun arg, u_short n = 0 ) const

inline

dump()

void ACE_SV_Semaphore_Complex::dump

(

)

const

Dump the state of an object.

get_id()

int ACE_SV_Semaphore_Simple::get_id ( ) const

inline

Get underlying internal id.

op() [1/2]

int ACE_SV_Semaphore_Complex::op ( sembuf op_vec[], u_short n ) const

inline

op() [2/2]

int ACE_SV_Semaphore_Complex::op ( short val, u_short n = 0, short flags = 0 ) const

inline

open() [1/2]

int ACE_SV_Semaphore_Complex::open	(	const char *	name,
		short	flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
		int	initial_value = 1,
		u_short	nsems = 1,
		mode_t	perms = ACE_DEFAULT_FILE_PERMS )

Open or create an array of SV_Semaphores. We return 0 if all is OK, else -1.

open() [2/2]

int ACE_SV_Semaphore_Complex::open	(	key_t	key,
		short	flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
		int	initial_value = 1,
		u_short	nsems = 1,
		mode_t	perms = ACE_DEFAULT_FILE_PERMS )

Open or create an array of SV_Semaphores. We return 0 if all is OK, else -1.

release()

int ACE_SV_Semaphore_Complex::release ( u_short n = 0, short flags = 0 ) const

inline

Release the semaphore.

remove()

int ACE_SV_Semaphore_Simple::remove

(

)

const

Remove all SV_Semaphores associated with a particular key. This call is intended to be called from a server, for example, when it is being shut down, as we do an IPC_RMID on the ACE_SV_Semaphore, regardless of whether other processes may be using it or not. Most other processes should use close() below.

tryacquire()

int ACE_SV_Semaphore_Complex::tryacquire ( u_short n = 0, short flags = 0 ) const

inline

Try to acquire the semaphore.

tryacquire_read()

int ACE_SV_Semaphore_Complex::tryacquire_read ( u_short n = 0, short flags = 0 ) const

inline

Try to acquire the semaphore for reading.

tryacquire_write()

int ACE_SV_Semaphore_Complex::tryacquire_write ( u_short n = 0, short flags = 0 ) const

inline

Try to acquire the semaphore for writing.

Member Data Documentation

ACE_ALLOC_HOOK_DECLARE

ACE_SV_Semaphore_Complex::ACE_ALLOC_HOOK_DECLARE

Declare the dynamic allocation hooks.

BIGCOUNT_

const int ACE_SV_Semaphore_Complex::BIGCOUNT_ = 10000

staticprivate

op_close_

sembuf ACE_SV_Semaphore_Complex::op_close_

staticprivate

Initial value:

=
{
  {0, 0, 0},                    
  {0, 1, SEM_UNDO},             
  {1, 1, SEM_UNDO},             
}

op_endcreate_

sembuf ACE_SV_Semaphore_Complex::op_endcreate_

staticprivate

Initial value:

=
{
  {1, -1, SEM_UNDO},            
                                
                                
  {0, -1, SEM_UNDO},            
}

op_lock_

sembuf ACE_SV_Semaphore_Complex::op_lock_

staticprivate

Initial value:

=
{
  {0, 0, 0},                    
  {0, 1, SEM_UNDO},             
                                
                                
}

op_open_

sembuf ACE_SV_Semaphore_Complex::op_open_

staticprivate

Initial value:

=
{
  {1, -1, SEM_UNDO},            
                                
}

op_unlock_

sembuf ACE_SV_Semaphore_Complex::op_unlock_

staticprivate

Initial value:

=
{
  {0, -1, SEM_UNDO},            
}

---

The documentation for this class was generated from the following files:

• SV_Semaphore_Complex.h
• SV_Semaphore_Complex.cpp
• SV_Semaphore_Complex.inl