boost进程间通信经常使用开发一篇全（消息队列，共享内存，信号）

本文概要：

敏捷开发大家想必知道并且评价甚高，缩短开发周期，提高开发质量。将大project独立为不同的小app开发，整个开发过程，程序可用可測，所以提高了总体的质量。基于这样的开发模式和开发理念，进程间通信必定是童鞋们必掌握技能之中的一个了，而boost库是众多库中平台支持性非常好，效果非常高之中的一个。做嵌入式或者server等应用的人肯定有所涉及。本文以手冊方式讲述boost共享内存，信号，以及消息队列的编程方式。非常easy，列出最经常使用使用方法，供大家拷贝直接使用。本文出自CSDN-固本培元。转载注明出处-leoluopy@gmail.com。

应用思路注意事项：

         信号是进程内通信，非常类似于Qt的信号槽，配合消息队列以及boost多线程使用效果非常好。

共享内存：

#include <boost/interprocess/shared_memory_object.hpp>
#include <boost/interprocess/mapped_region.hpp>
#include <cstring>
#include <cstdlib>
#include <string>  

int main(int argc, char *argv[])
{
   using namespace boost::interprocess;  

   if(argc == 1){  //Parent process
      //Remove shared memory on construction and destruction
      struct shm_remove
      {
         shm_remove() { shared_memory_object::remove("MySharedMemory"); }
         ~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
      } remover;  

      //Create a shared memory object.
      shared_memory_object shm (create_only, "MySharedMemory", read_write);  

      //Set size
      shm.truncate(1000);  

      //Map the whole shared memory in this process
      mapped_region region(shm, read_write);  

      //Write all the memory to 1
      std::memset(region.get_address(), 1, region.get_size());  

      //Launch child process
      std::string s(argv[0]); s += " child ";
      if(0 != std::system(s.c_str()))
         return 1;
   }
   else{
      //Open already created shared memory object.
      shared_memory_object shm (open_only, "MySharedMemory", read_only);  

      //Map the whole shared memory in this process
      mapped_region region(shm, read_only);  

      //Check that memory was initialized to 1
      char *mem = static_cast<char*>(region.get_address());
      for(std::size_t i = 0; i < region.get_size(); ++i)
         if(*mem++ != 1)
            return 1;   //Error checking memory
   }
   return 0;
} 

信号通信：

贴出一个经常使用带參数的写法，具体的其它使用方法能够參考文章末的參考文章：

#include <boost/signal.hpp>

#include <boost/thread/thread.hpp>

#include <boost/date_time/posix_time/posix_time.hpp>

#include <iostream>

using namespace std;

using namespace boost;

float print_sum(float x, float y)

{

  std::cout << "The sum is " << x+y << std::endl;

  return x+y;

}

float print_product(float x, float y)

{

  std::cout << "The product is " << x*y << std::endl;

  return x*y;

}

float print_difference(float x, float y)

{

  std::cout << "The difference is " << x-y << std::endl;

  return x-y;

}

float print_quotient(float x, float y)

{

  std::cout << "The quotient is " << x/y << std::endl;

  return x/y;

}

int main()

{

  boost::signal<float (float , float )> sig;

  sig.connect(0, &print_sum);

  sig.connect(1, &print_product);

  sig.connect(2, &print_difference);

  sig.connect(3, &print_quotient);

  // Output 1.6667 because return by the last slot called.

  cout << sig(5, 3) << endl;   

  return 0;

}

信号槽删除及堵塞：

Seg 1: Disconnecting slots.

        boost::signals::connection c = sig.connect(HelloWorld());

        if (c.connected()) {

        // c is still connected to the signal

        sig(); // Prints "Hello, World!"

        }

        c.disconnect(); // Disconnect the HelloWorld object

        assert(!c.connected()); //c isn't connected any more

        sig(); // Does nothing: there are no connected slots

Seg 2:

        boost::signals::connection c = sig.connect(HelloWorld());

        sig(); // Prints "Hello, World!"

        c.block(); // block the slot

        assert(c.blocked());

        sig(); // No output: the slot is blocked

        c.unblock(); // unblock the slot

        sig(); // Prints "Hello, World!"

消息队列：

消息队列发送：

#include <boost/interprocess/ipc/message_queue.hpp>
#include <iostream>
#include <vector>

using namespace boost::interprocess;

int main ()
{
   try{
      //Erase previous message queue
      message_queue::remove("message_queue");

      //Create a message_queue.
      message_queue mq
         (create_only               //only create
         ,"message_queue"           //name
         ,100                       //max message number
         ,sizeof(int)               //max message size
         );

      //Send 100 numbers
      for(int i = 0; i < 100; ++i){
         mq.send(&i, sizeof(i), 0);
      }

   }
   catch(interprocess_exception &ex){
      std::cout << ex.what() << std::endl;
      return 1;
   }

   return 0;
}

消息队列接收：

#include <boost/interprocess/ipc/message_queue.hpp>
#include <iostream>
#include <vector>

using namespace boost::interprocess;

int main ()
{
   try{
      //Open a message queue.
      message_queue mq
         (open_only        //only create
         ,"message_queue"  //name
         );

      unsigned int priority;
      message_queue::size_type recvd_size;

      //Receive 100 numbers
      for(int i = 0; i < 100; ++i)
	  {
         int number;
         mq.receive(&number, sizeof(number), recvd_size, priority);
		 printf("I:%d Rec:%d\n",i,number);
         if(number != i || recvd_size != sizeof(number))
            return 1;
      }
   }
   catch(interprocess_exception &ex){
      message_queue::remove("message_queue");
      std::cout << ex.what() << std::endl;
      return 1;
   }
   message_queue::remove("message_queue");
   return 0;
}

编译命令：

[root@localhost tmp]# g++ boost_queue_send.cpp -o queue_send -lboost_thread -lboost_system
[root@localhost tmp]# g++ boost_queue_rec.cpp -o queue_rec -lboost_thread -lboost_system

将消息队列整理了一下，能够直接方便使用例如以下：

注（BoostMsg.h）用于将函数外部化，无其它用处。

#include <BoostMsg.h>

#include <boost/interprocess/ipc/message_queue.hpp>
#include <iostream>
#include <vector>  

using namespace boost::interprocess;  

int BoostMsg_CreateMsg(const char* MsgQueName,int MaxQueLen,int MaxMsgLen)
{
	message_queue::remove(MsgQueName);
	//Create a message_queue.
	message_queue mq
		(create_only               //only create
		,MsgQueName						//name
		,MaxQueLen                       //max message number
		,MaxMsgLen              //max message size
		);  

	printf("Boost Msg Created Name:%s QueLen:%d MsgMaxLen:%d \n",MsgQueName,MaxQueLen,MaxMsgLen);

	return 0;
}

int BoostMsg_OpenMsgToSend(char* BufMsg,const char* MsgQueName,int MsgLen)
{
	try{
		//Erase previous message queue
		//message_queue::remove("message_queue");
		//Create a message_queue.
		message_queue mq
			(open_only               //only create
			,MsgQueName						//name
			);  

		mq.send(BufMsg, MsgLen, 0);
	}
	catch(interprocess_exception &ex){
		std::cout << ex.what() << std::endl;
		return 1;
	}
	return 0;
} 

int BoostMsg_OpenMsgToRec(char* RecivedMsg,const char* MsgQueName,int MaxReceivedLen)
{
	try{
		//Open a message queue.
		message_queue mq
			(open_only        //only create
			,MsgQueName  //name
			);  

		unsigned int priority;
		message_queue::size_type recvd_size;  

		memset(RecivedMsg,0,MaxReceivedLen);
		mq.receive(RecivedMsg, MaxReceivedLen, recvd_size, priority);
		return recvd_size;

	}
	catch(interprocess_exception &ex){
		message_queue::remove("message_queue");
		std::cout << ex.what() << std::endl;
		return 1;
	}
	message_queue::remove("message_queue");
	return 0;
}

用法非常easy，就是Create 然后Send 和Rec，进程之间通信 非常方便。

參考文章：

Boost.Interprocess使用手冊翻译之四：在进程间共享内存 （Sharing
memory between processes）

http://blog.csdn.net/great3779/article/details/7226388

Windows多进程编程

http://blog.csdn.net/bxhj3014/article/details/2082255

怎样使用BOOST信号(一)

http://blog.csdn.net/liuchangyu23/article/details/4584045

Boost.Interprocess 强大的进程间通讯库

http://blog.csdn.net/linkerlin/article/details/2249906

怎样使用BOOST信号(二)

http://blog.csdn.net/liuchangyu23/article/details/4584346