ACE  6.1.0
Public Types | Public Member Functions | Public Attributes | Static Private Attributes
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:
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Collaboration diagram for ACE_SV_Semaphore_Complex:
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List of all members.

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

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]

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.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Acquire a semaphore for reading.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Acquire a semaphore for writing.

Reimplemented from ACE_SV_Semaphore_Simple.

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.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Reimplemented from ACE_SV_Semaphore_Simple.

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

Reimplemented from ACE_SV_Semaphore_Simple.

void ACE_SV_Semaphore_Complex::dump ( void  ) const

Dump the state of an object.

Reimplemented from ACE_SV_Semaphore_Simple.

int ACE_SV_Semaphore_Complex::op ( short  val,
u_short  semnum = 0,
short  flags = 0 
) const [inline]

General ACE_SV_Semaphore operation. Increment or decrement by a specific amount (positive or negative; amount can`t be zero).

Reimplemented from ACE_SV_Semaphore_Simple.

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

General ACE_SV_Semaphore operation on an array of SV_Semaphores.

Reimplemented from ACE_SV_Semaphore_Simple.

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.

Reimplemented from ACE_SV_Semaphore_Simple.

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.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Release the semaphore.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Try to acquire the semaphore.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Try to acquire the semaphore for reading.

Reimplemented from ACE_SV_Semaphore_Simple.

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

Try to acquire the semaphore for writing.

Reimplemented from ACE_SV_Semaphore_Simple.


Member Data Documentation

Declare the dynamic allocation hooks.

Reimplemented from ACE_SV_Semaphore_Simple.

const int ACE_SV_Semaphore_Complex::BIGCOUNT_ = 10000 [static, private]
sembuf ACE_SV_Semaphore_Complex::op_close_ [static, private]
Initial value:
{
  {0, 0, 0},                    
  {0, 1, SEM_UNDO},             
  {1, 1, SEM_UNDO},             
}
sembuf ACE_SV_Semaphore_Complex::op_endcreate_ [static, private]
Initial value:
{
  {1, -1, SEM_UNDO},            
                                
                                
  {0, -1, SEM_UNDO},            
}
sembuf ACE_SV_Semaphore_Complex::op_lock_ [static, private]
Initial value:
{
  {0, 0, 0},                    
  {0, 1, SEM_UNDO},             
                                
                                
}
sembuf ACE_SV_Semaphore_Complex::op_open_ [static, private]
Initial value:
{
  {1, -1, SEM_UNDO},            
                                
}
sembuf ACE_SV_Semaphore_Complex::op_unlock_ [static, private]
Initial value:
{
  {0, -1, SEM_UNDO},            
}

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