IPCMutex.cpp

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#include "blocxx/BLOCXX_config.h"

#ifdef BLOCXX_GNU_LINUX
#include "blocxx/IPCMutex.hpp"
#include "blocxx/ExceptionIds.hpp"


namespace BLOCXX_NAMESPACE
{

const int ADD_KEY = 1; 
const int BLOCK_FOR_KEY = -1; 

BLOCXX_DEFINE_EXCEPTION_WITH_ID(IPCMutex);


IPCMutex::IPCMutex(int semKey)
{
   m_sbuf.sem_num = 0; 
   m_sbuf.sem_flg = 0; 
   m_semid = semget((key_t)semKey, 1, 0666); 
   if (m_semid == -1)
   {
      m_semid = semget((key_t)semKey, 1, IPC_CREAT | 0666); 
      if (m_semid == -1)
      {
         BLOCXX_THROW(IPCMutexException, 
                   "Unable to create semaphore"); 
         return; 
      }
      m_arg.val = 1; 
      if (semctl(m_semid, 0, SETVAL, m_arg) != 0)
      {
         BLOCXX_THROW_ERRNO_MSG(IPCMutexException, 
            "semctl() failed"); 
      }
   }
}

void
IPCMutex::wait()
{
   m_sbuf.sem_op = BLOCK_FOR_KEY; 
   if (semop(m_semid, &m_sbuf, 1) != 0)
   {
      BLOCXX_THROW_ERRNO_MSG(IPCMutexException, 
         "Failed to wait on semaphore"); 
   }
}

void
IPCMutex::signal()
{
   m_sbuf.sem_op = ADD_KEY; 
   if (semop(m_semid, &m_sbuf, 1) != 0)
   {
      BLOCXX_THROW_ERRNO_MSG(IPCMutexException, 
         "Failed to signal semaphore"); 
   }
}

// static 
void
IPCMutex::free(int semKey)
{
   int semid = semget((key_t)semKey, 1, 0666); 
   if (semid != -1)
   {
      semctl(semid, 1, IPC_RMID, 0); 
   }
}

IPCMutexLock::IPCMutexLock(IPCMutex& sem)
: m_sem(sem)
{
   m_sem.wait(); 
}

IPCMutexLock::~IPCMutexLock()
{
   m_sem.signal(); 
}

}

#endif // BLOCXX_GNU_LINUX