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/* -*- C++ -*- */
//=============================================================================
/**
* @file SV_Semaphore_Complex.h
*
* $Id$
*
* @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
*/
//=============================================================================
#ifndef ACE_SV_SEMAPHORE_COMPLEX_H
#define ACE_SV_SEMAPHORE_COMPLEX_H
#include "ace/pre.h"
#include "ace/SV_Semaphore_Simple.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
/**
* @class ACE_SV_Semaphore_Complex
*
* @brief 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.
*/
class ACE_Export ACE_SV_Semaphore_Complex : private ACE_SV_Semaphore_Simple
{
public:
enum
{
ACE_CREATE = IPC_CREAT,
ACE_OPEN = 0
};
// = Initialization and termination methods.
ACE_SV_Semaphore_Complex (void);
ACE_SV_Semaphore_Complex (key_t key,
int create = ACE_SV_Semaphore_Complex::ACE_CREATE,
int initial_value = 1,
u_short nsems = 1,
int perms = ACE_DEFAULT_FILE_PERMS);
ACE_SV_Semaphore_Complex (const char *name,
int create = ACE_SV_Semaphore_Complex::ACE_CREATE,
int initial_value = 1,
u_short nsems = 1,
int perms = ACE_DEFAULT_FILE_PERMS);
~ACE_SV_Semaphore_Complex (void);
/// Open or create an array of SV_Semaphores. We return 0 if all is
/// OK, else -1.
int open (const char *name,
int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
int initial_value = 1,
u_short nsems = 1,
int perms = ACE_DEFAULT_FILE_PERMS);
/// Open or create an array of SV_Semaphores. We return 0 if all is
/// OK, else -1.
int open (key_t key,
int flags = ACE_SV_Semaphore_Simple::ACE_CREATE,
int initial_value = 1,
u_short nsems = 1,
int perms = ACE_DEFAULT_FILE_PERMS);
/**
* 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 close (void);
// = Semaphore acquire and release methods.
/// Acquire the semaphore.
int acquire (u_short n = 0, int flags = 0) const;
/// Acquire a semaphore for reading.
int acquire_read (u_short n = 0, int flags = 0) const;
/// Acquire a semaphore for writing
int acquire_write (u_short n = 0, int flags = 0) const;
/// Try to acquire the semaphore.
int tryacquire (u_short n = 0, int flags = 0) const;
/// Try to acquire the semaphore for reading.
int tryacquire_read (u_short n = 0, int flags = 0) const;
/// Try to acquire the semaphore for writing.
int tryacquire_write (u_short n = 0, int flags = 0) const;
/// Release the semaphore.
int release (u_short n = 0, int flags = 0) const;
// = Semaphore operation methods.
int op (int val, u_short n = 0, int flags = 0) const;
int op (sembuf op_vec[], u_short n) const;
// = Semaphore control methods.
int control (int cmd, semun arg, u_short n = 0) const;
int control (int cmd, int value = 0, u_short n = 0) const;
// = Upgrade access control...
ACE_USING ACE_SV_Semaphore_Simple::get_id;
ACE_USING ACE_SV_Semaphore_Simple::remove;
/// Dump the state of an object.
void dump (void) const;
/// Declare the dynamic allocation hooks.
ACE_ALLOC_HOOK_DECLARE;
private:
static const int BIGCOUNT_;
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];
};
#if !defined (ACE_LACKS_INLINE_FUNCTIONS)
#include "ace/SV_Semaphore_Complex.i"
#endif
#include "ace/post.h"
#endif /* ACE_SV_SEMAPHORE_COMPLEX_H */
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