shared_mem_manager.cpp

/****************************************************************************
 Copyright (c) 2015, ko jung hyun
 
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 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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#include "shared_mem_manager.hpp" 
#include "common_def.hpp"

///////////////////////////////////////////////////////////////////////////////
SharedMemoryManager::SharedMemoryManager(): 
    sh_mem_id_(-1), sh_mem_size_(0), sh_mem_start_addr_(NULL) , total_attached_(0)
{
}

///////////////////////////////////////////////////////////////////////////////
bool SharedMemoryManager::CreateShMem(key_t key, size_t size, bool* is_first_created)
{            
    *is_first_created = false;
    sh_mem_key_  = key ;
    sh_mem_size_ = size;
    sh_mem_id_ = shmget((key_t)key, size, IPC_CREAT | IPC_EXCL | 0666 ); //IPC_CREAT | IPC_EXCL 

    if (sh_mem_id_ < 0) {
        if(errno == EINVAL ) {
            err_msg_ = std::string("shmget error: key [ ") + 
                       std::to_string(key) + std::string(strerror(errno)) ;
            DEBUG_ELOG(err_msg_);
        } else if(errno == EEXIST || errno == EACCES ) {
            return GetShMem(key,size);
        } else {
            err_msg_ = std::string("shmget error: key [ ") + 
                       std::to_string(key) + std::string(strerror(errno)) ;
            DEBUG_ELOG(err_msg_);
        }
        return false;
    }
    *is_first_created = true;
    return true;
}

///////////////////////////////////////////////////////////////////////////////
bool SharedMemoryManager::GetShMem(key_t key, size_t size)
{            
    sh_mem_key_  = key ;
    sh_mem_size_ = size;

    sh_mem_id_ = shmget((key_t)key, size, 0666 );
    if (sh_mem_id_ < 0) {
        err_msg_ = "shmget error: " + std::string(strerror(errno)) ;
        DEBUG_ELOG(err_msg_);
        return false;
    }
    return true;
}

///////////////////////////////////////////////////////////////////////////////
bool SharedMemoryManager::AttachShMem()
{            
	sh_mem_start_addr_ = shmat(sh_mem_id_ , NULL, 0);

	if (sh_mem_start_addr_ == (void *) -1) {
        DEBUG_ELOG("shmat error: "<< strerror(errno) <<",sh_mem_id_="<<sh_mem_id_);
		return false;
	}
    total_attached_ ++ ;
    return true;
}

///////////////////////////////////////////////////////////////////////////////
bool SharedMemoryManager::DetachShMem()
{            
	if (sh_mem_start_addr_ == NULL) {
        DEBUG_ELOG("Error : shared mem start addr is NULL");
		return false;
    }
	if (shmdt(sh_mem_start_addr_) == -1) {
        DEBUG_ELOG("shmdt error: "<< strerror(errno) );
		return false;
	}
    total_attached_ -- ;
    return true;
}

///////////////////////////////////////////////////////////////////////////////
bool SharedMemoryManager::RemoveShMem()
{            
    if(total_attached_ > 0 ) {
        DEBUG_ELOG("Error : attached exists :" <<total_attached_ );
		return false;
    }
    if (shmctl(sh_mem_id_, IPC_RMID, (struct shmid_ds *)NULL) == -1) {
        DEBUG_ELOG("Remove shared memoey error: "<< strerror(errno) );
		return false;
    }
    return true;
}