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 (void)

	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 (void)

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 (void)

int	acquire (u_short n=0, short flags=0) const
	Acquire the semaphore. More...

int	acquire_read (u_short n=0, short flags=0) const
	Acquire a semaphore for reading. More...

int	acquire_write (u_short n=0, short flags=0) const
	Acquire a semaphore for writing. More...

int	tryacquire (u_short n=0, short flags=0) const
	Try to acquire the semaphore. More...

int	tryacquire_read (u_short n=0, short flags=0) const
	Try to acquire the semaphore for reading. More...

int	tryacquire_write (u_short n=0, short flags=0) const
	Try to acquire the semaphore for writing. More...

int	release (u_short n=0, short flags=0) const
	Release the semaphore. More...

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 (void) const
	Dump the state of an object. More...

Public Attributes
	ACE_ALLOC_HOOK_DECLARE
	Declare the dynamic allocation hooks. More...

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 (void)

	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 (void)

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 (void)

int	remove (void) 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. More...

int	acquire_write (u_short n=0, short flags=0) const
	Acquire a semaphore for writing. More...

int	tryacquire (u_short n=0, short flags=0) const
	Non-blocking version of <acquire>. More...

int	tryacquire_read (u_short n=0, short flags=0) const
	Try to acquire the semaphore for reading. More...

int	tryacquire_write (u_short n=0, short flags=0) const
	Try to acquire the semaphore for writing. More...

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. More...

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 (void) const
	Get underlying internal id. More...

void	dump (void) const
	Dump the state of an object. More...

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. More...

key_t	key_
	Semaphore key. More...

int	internal_id_
	Internal ID to identify the semaphore group within this process. More...

int	sem_number_
	Number of semaphores we're creating. More...

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

Enumerator
ACE_CREATE
ACE_OPEN

Constructor & Destructor Documentation

ACE_SV_Semaphore_Complex::ACE_SV_Semaphore_Complex ( void )

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::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 ( void )

Member Function Documentation

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

inline

Acquire the semaphore.

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

inline

Acquire a semaphore for reading.

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

inline

Acquire a semaphore for writing.

int ACE_SV_Semaphore_Complex::close ( void )

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.

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

inline

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

inline

void ACE_SV_Semaphore_Complex::dump ( void ) const

Dump the state of an object.

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

inline

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

inline

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.

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.

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

inline

Release the semaphore.

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

inline

Try to acquire the semaphore.

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

inline

Try to acquire the semaphore for reading.

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_SV_Semaphore_Complex::ACE_ALLOC_HOOK_DECLARE

Declare the dynamic allocation hooks.

const int ACE_SV_Semaphore_Complex::BIGCOUNT_ = 10000

staticprivate

sembuf ACE_SV_Semaphore_Complex::op_close_

staticprivate

Initial value:

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

sembuf ACE_SV_Semaphore_Complex::op_endcreate_

staticprivate

Initial value:

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

sembuf ACE_SV_Semaphore_Complex::op_lock_

staticprivate

Initial value:

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

sembuf ACE_SV_Semaphore_Complex::op_open_

staticprivate

Initial value:

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

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:

Public Types

Public Member Functions

Public Attributes

Static Private Attributes

Additional Inherited Members

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation