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/* -*- C++ -*- */
// $Id$
// ============================================================================
//
// = LIBRARY
// ace
//
// = FILENAME
// ACE_SV_Semaphore_Complex.h
//
// = AUTHOR
// Doug Schmidt
//
// ============================================================================
#ifndef ACE_SV_SEMAPHORE_COMPLEX_H
#define ACE_SV_SEMAPHORE_COMPLEX_H
#include "ace/SV_Semaphore_Simple.h"
#if !defined (ACE_LACKS_PRAGMA_ONCE)
#pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */
class ACE_Export ACE_SV_Semaphore_Complex : private ACE_SV_Semaphore_Simple
{
// = TITLE
// This is a more complex semaphore wrapper that handles race
// conditions for initialization correctly...
//
// = DESCRIPTION
// 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) ACE_SV_Semaphore Interface: we provide
// a simpler and easier to understand interface to the System V
// ACE_SV_Semaphore calls. We create and use a 2 + n-member
// set for the requested ACE_SV_Semaphore. The first member,
// [0], is a counter used to know when all processes have
// finished with the ACE_SV_Semaphore. 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) but it will work if any process other than
// the last does an exit (intentional or unintentional).
//
// The second member, [1], of the ACE_SV_Semaphore is used as a
// lock variable to avoid any race conditions in the create()
// and close() functions.
//
// The members beyond [1] are actual ACE_SV_Semaphore values in
// the array of SV_Semaphores (which may be sized by the user
// in the constructor).
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);
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);
// Open or create an array of SV_Semaphores. We return 0 if all is
// OK, else -1.
int 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.
// = Semaphore acquire and release methods.
int acquire (u_short n = 0, int flags = 0) const;
// Acquire the semaphore.
int acquire_read (u_short n = 0, int flags = 0) const;
// Acquire a semaphore for reading.
int acquire_write (u_short n = 0, int flags = 0) const;
// Acquire a semaphore for writing
int tryacquire (u_short n = 0, int flags = 0) const;
// Try to acquire the semaphore.
int tryacquire_read (u_short n = 0, int flags = 0) const;
// Try to acquire the semaphore for reading.
int tryacquire_write (u_short n = 0, int flags = 0) const;
// Try to acquire the semaphore for writing.
int release (u_short n = 0, int flags = 0) const;
// Release the semaphore.
// = 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;
void dump (void) const;
// Dump the state of an object.
ACE_ALLOC_HOOK_DECLARE;
// Declare the dynamic allocation hooks.
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
#endif /* ACE_SV_SEMAPHORE_COMPLEX_H */
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