TarsCpp/util/src/tc_shm.cpp

/**
 * Tencent is pleased to support the open source community by making Tars available.
 *
 * Copyright (C) 2016THL A29 Limited, a Tencent company. All rights reserved.
 *
 * Licensed under the BSD 3-Clause License (the "License"); you may not use this file except 
 * in compliance with the License. You may obtain a copy of the License at
 *
 * https://opensource.org/licenses/BSD-3-Clause
 *
 * Unless required by applicable law or agreed to in writing, software distributed 
 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the 
 * specific language governing permissions and limitations under the License.
 */

#include "util/tc_shm.h"
#include "util/tc_common.h"
#include <cassert>
#include <errno.h>

namespace tars
{

TC_Shm::TC_Shm(size_t iShmSize, key_t iKey, bool bOwner) : _pshm(NULL)
{
    init(iShmSize, iKey, bOwner);
}

TC_Shm::~TC_Shm()
{
    if (_bOwner)
    {
        detach();
    }
}

void TC_Shm::init(size_t iShmSize, key_t iKey, bool bOwner)
{
    assert(_pshm == NULL);

#if TARGET_PLATFORM_WINDOWS
    // 首先试图打开一个命名的内存映射文件对象  
    HANDLE hMap = ::OpenFileMapping(FILE_MAP_ALL_ACCESS, 0, TC_Common::tostr(iKey).c_str());
    if (NULL == hMap)
    {    
        // 打开失败，创建之
        hMap = ::CreateFileMapping(INVALID_HANDLE_VALUE, NULL,PAGE_READWRITE,0, iShmSize, TC_Common::tostr(iKey).c_str());
        // 映射对象的一个视图，得到指向共享内存的指针，设置里面的数据
        _pshm = ::MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);
    }
    else
    {    // 打开成功，映射对象的一个视图，得到指向共享内存的指针，显示出里面的数据
        _pshm = ::MapViewOfFile(hMap, FILE_MAP_ALL_ACCESS, 0, 0, 0);
    }

    _shemID = hMap;
    _shmKey = iKey;
#else
    _bOwner     = bOwner;

    //注意_bCreate的赋值位置:保证多线程用一个对象的时候也不会有问题
    //试图创建
    if ((_shemID = shmget(iKey, iShmSize, IPC_CREAT | IPC_EXCL | 0666)) < 0)
    {
        _bCreate = false;
        //有可能是已经存在同样的key_shm,则试图连接
        if ((_shemID = shmget(iKey, iShmSize, 0666)) < 0)
        {
            THROW_EXCEPTION_SYSCODE(TC_Shm_Exception, "[TC_Shm::init()] shmget error");
            // throw TC_Shm_Exception("[TC_Shm::init()] shmget error", TC_Exception::getSystemCode());
        }
    }
    else
    {
        _bCreate    = true;
    }

    //try to access shm
    if ((_pshm = shmat(_shemID, NULL, 0)) == (char *) - 1)
    {
        THROW_EXCEPTION_SYSCODE(TC_Shm_Exception, "[TC_Shm::init()] shmat error");
        // throw TC_Shm_Exception("[TC_Shm::init()] shmat error", TC_Exception::getSystemCode());
    }

    _shmSize = iShmSize;
    _shmKey = iKey;
#endif    
}

int TC_Shm::detach()
{
#if TARGET_PLATFORM_WINDOWS    
    if (_pshm != NULL)
    {
        UnmapViewOfFile(_pshm);
        CloseHandle(_shemID);
    }
    return 0;
#else
    int iRetCode = 0;
    if (_pshm != NULL)
    {
        iRetCode = shmdt(_pshm);

        _pshm = NULL;
    }

    return iRetCode;

 #endif   
}

int TC_Shm::del()
{
#if TARGET_PLATFORM_WINDOWS    
    return 0;
#else
    int iRetCode = 0;
    if (_pshm != NULL)
    {
        iRetCode = shmctl(_shemID, IPC_RMID, 0);

        _pshm = NULL;
    }

    return iRetCode;
#endif

}

}