sem4.cpp

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/******************************************************************************\
sem4.cpp                        Neal Kettler
 
Simple Posix semaphore class
This is useful because the constructor will automatically call sem_init
  and you don't have to worry about it.  It also allows for other semaphore
  libraries if you don't have posix.
\******************************************************************************/
 
#include "sem4.h"
 
#ifdef _REENTRANT
 
Sem4::Sem4()
{
#ifndef _WINDOWS
  sem_init(&sem,1,1);
#else
  sem = CreateSemaphore(NULL, 1, 1, NULL);
#endif
}
 
Sem4::Sem4(uint32 value)
{
#ifndef _WINDOWS
  sem_init(&sem,1,value);
#else
  sem = CreateSemaphore(NULL, value, value, NULL);
#endif
}
 
Sem4::~Sem4()
{
#ifndef _WINDOWS
  sem_destroy(&sem);
#else
  if (sem) CloseHandle(sem);
#endif
}
 
sint32  Sem4::Wait(void) const
{
#ifndef _WINDOWS
    return(sem_wait((sem_t *)&sem));
#else
    if (!sem)
        return -1; // no semaphore!
 
    DWORD dwWaitResult = WaitForSingleObject(sem, INFINITE);
    switch (dwWaitResult) { 
    case WAIT_OBJECT_0: // The semaphore object was signaled.
        return 0;
        break;
    case WAIT_TIMEOUT: // Should not happen ;)
        return -1;
        break; 
    }
    return -1;
#endif
} 
 
sint32 Sem4::Post(void) const
{
#ifndef _WINDOWS
  return(sem_post((sem_t *)&sem));
#else
  if (!sem)
      return -1;
  if (!ReleaseSemaphore(sem, 1 ,NULL))
      return -1;
  return 0;
#endif
}
 
sint32 Sem4::TryWait(void) const
{
#ifndef _WINDOWS
  return(sem_trywait((sem_t *)&sem));
#else
    if (!sem)
        return -1;
    DWORD dwWaitResult = WaitForSingleObject(sem, 0L);
    switch (dwWaitResult) { 
    case WAIT_OBJECT_0: // The semaphore object was signaled.
        return 0;
        break;
    case WAIT_TIMEOUT:
        return -1;
        break; 
    }
    return -1;
#endif
}
 
sint32 Sem4::GetValue(int *sval) const
{
#ifndef _WINDOWS
  return(sem_getvalue((sem_t *)&sem,sval));
#else
    if (!sem)
        return -1;
    long prev;
    if (!ReleaseSemaphore(sem, 0, &prev))
        return -1;
    if (sval)
        *sval = prev;
    return 0;
#endif
}
 
sint32 Sem4::Destroy(void)
{
#ifndef _WINDOWS
  return(sem_destroy(&sem));
#else
  return CloseHandle(sem);
#endif
}
 
#else  
 
/****************************************************************************
non threaded versions that do nothing
*****************************************************************************/
 
Sem4::Sem4()
{
}
 
Sem4::Sem4(uint32)
{
}
 
Sem4::~Sem4()
{
}
 
sint32  Sem4::Wait(void) const
{
  return(0);
} 
 
sint32 Sem4::Post(void) const
{
  return(0);
}
 
sint32 Sem4::TryWait(void) const
{
  return(0);
}
 
sint32 Sem4::GetValue(int *) const
{
  return(0);
}
 
sint32 Sem4::Destroy(void)
{
  return(0);
}
 
#endif