Re: [Boost-users] thread_group / removal of items

Subject: Re: [Boost-users] thread_group / removal of items
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-12-13 08:01:55

----- Original Message ----- 
From: "Christian Ost" <christian.ost_at_[hidden]>
To: <boost-users_at_[hidden]>
Sent: Wednesday, August 27, 2008 6:06 PM
Subject: [Boost-users] thread_group / removal of items

> 
> Hi,
> 
> I have a question concerning the removal from entries of a thread_group.
> Consider the following code (i am working on a small threaded server):
> 
> in TCPServer.h:
> 
> boost::thread_group threads
> 
> in TCPServer.cpp:
> 
> int TCPServer::loop(int listen_fd) {
>  for (;;) {
>      [connect client]
>      boost::thread* thrd = new
> boost::thread(boost::bind(&TCPServer::readMessages, this, rfd));
>      threads.add_thread(thrd);
>    }
>  }
> }
> 
> int TCPServer::readMessages(int rfd) {
>  boost::this_thread::at_thread_exit(boost::bind(&TCPServer::exitThread, this));
>  for(;;) {
>    [read message]
>    if ([buffer is empty]) {
>      [close connection]
>      return(0);
>    }
>  }
>  return 1;
> }
> 
> void TCPServer::exitThread() {
>  cout << "thread exited" << endl;
> }
> 
> 
> Now I would like to remove the exited thread from the thread_group,
> however to do this
> I would need its thread* object - but the maximum of information I can get from
> boost::this_thread is a boost::thread::id and I haven't found a
> possibility to get a thread
> by its thread::id so far.
> 
> How can/should I solve this issue?
> I would be quite happy about any advice...

Hi,

I suppose that you have find a solution. Anyway here they are some hits:
you can pass the thread* tp and the thread_group to the thread function

shared_ptr<thread> tp;
tp.reset(threads.create_thread(boost::bind(&TCPServer::readMessages, this, rfd, tp, threads)));

int TCPServer::readMessages(int rfd, shared_ptr<thread>th_ptr, thread_group& tg) {

    //..
    tg.remove_thread(th_ptr.get());
    //...
}

This is safe because the thread_group class is thread _safe.

If the thread_group stores the thread::id instead of the thread pointer, it can provide a function 
    remove_thread(thread:id);

Given a thread* we can alway get the thread::id but the contrary is false.
The thread_group class is not to big. You can adapt it waiting for the feature to be in threads.

Best,
Vicente