/* SSemaphore.h
  A VERY simplified semaphore class for use in a std UNIX
  environment.  See the text for instructions on how to use
  this class.  Copyright (c) 2002 J. S. Gray

  Exit codes for class operations:

  1 - Semaphore allocation failure   2 - Unable remove semaphore
  3 - Unable to LOCK semaphore       4 - Unable to UNLOCK semaphore
  5 - Failure on wait for ZERO       6 - Unable to assign value
  7 - Unable to return value
*/

#ifndef SSemaphore_h
#define SSemaphore_h
#define _GNU_SOURCE
#include <iostream>
#include <cstdio>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdlib.h>
#include <unistd.h>
using namespace std;

class SSemaphore {
  public:
    SSemaphore ( );                 // Constructor
    ~SSemaphore( );                 // Destructor - remove semaphore
    int  P( );                      // LOCK (decrement semaphore)
    void V( );                      // UNLOCK (increment semaphore)
    int  Z( );                      // WAIT while semaphore is NOT 0
    void Put( const int );          // Assign a value to semaphore
    int  Get( );                    // Return value of the semaphore
  private:
    #if defined(__GNU_LIBRARY__) && !defined(_SEM_SEMUN_UNDEFINED)
                                    // definition in <sys/sem.h>
    #else
    union semun {                   // We define:
      int val;                      // value  for SETVAL
      struct semid_ds *buf;         // buffer for IPC_STAT, IPC_SET
      unsigned short int *array;    // array  for GETALL, SETALL
      struct seminfo *__buf;        // buffer for IPC_INFO
    };
    #endif
    union  semun  arg;              // For semctl call
    struct sembuf zero,lock, unlock; // hoo ha's for P,V & Z operations
    int   semid;                    // ID of semaphore
    pid_t my_pid;                   // PID of creator
};
#endif