shm.cpp

一套linux下的C++开发库

/***************************************************************************
                          shm.cpp  -  description
                             -------------------
    begin                : Fri Jul 20 2001
    copyright            : (C) 2001 by Mark
    email                : [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/


#include <errno.h>

#include "shm.h"


CShm::CShm(key_t tKey, int iSize, int iMode)
		: m_tShmKey(tKey), m_iShmSize(iSize)
{
	GetShm(iMode);
	AttachShm();
}


CShm::~CShm()
{
	DetachShm();
}


void CShm::GetShm(int iMode)
{
	if ((m_iShmId = shmget(m_tShmKey, m_iShmSize, IPC_CREAT | IPC_EXCL | iMode)) < 0)	//try to create
	{
		if (errno != EEXIST)
			throw CShmException(strerror(errno), __FILE__, __LINE__);

		if ((m_iShmId = shmget(m_tShmKey, m_iShmSize, iMode)) < 0)
			throw CShmException(strerror(errno), __FILE__, __LINE__);

		m_bCreate = false;
		return;
	}

	m_bCreate = true;
}


void CShm::AttachShm()
{
  if ((m_pchShm = (char*)shmat(m_iShmId, NULL, 0)) < 0)
		throw CShmException(strerror(errno), __FILE__, __LINE__);
}


void CShm::DetachShm()
{
	if (shmdt(m_pchShm) < 0)
		throw CShmException(strerror(errno), __FILE__, __LINE__);
}


void CShm::RemoveShm()
{
	if (shmctl(m_iShmId, IPC_RMID, NULL) < 0)
		throw CShmException(strerror(errno), __FILE__, __LINE__);
}


void CShm::InitShm()
{
	memset(m_pchShm, 0, m_iShmSize);
}