Re: using std::deque in multiple threads

From:
"PaulH" <paul.heil@gmail.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
16 Aug 2006 07:44:22 -0700
Message-ID:
<1155739462.420074.113790@74g2000cwt.googlegroups.com>
It was CRITICAL_SECTION, so thank you for pointing that out.

-PaulH

Joseph M. Newcomer wrote:

Passing by reference like that can present problems. You have also not said what the
variable type m_cs is; it can't be CRITICAL_SECTION because that would cause a copy, which
probably won't work right. A CRITICAL_SECTION* will work. Note that the variable must
exist for the entire duration of the threads that use it.
                joe

On 15 Aug 2006 15:30:32 -0700, "PaulH" <paul.heil@gmail.com> wrote:

What's a good way to pass the CRITICAL_SECTION object from my main
class with the thread to my dialog class with the list?

Something like this?

CMyDlg::SetCritObj(const CRITICAL_SECTION &cs)
{
 m_cs = cs;
}

Thanks,
PaulH

Scott McPhillips [MVP] wrote:

Create a CRITICAL_SECTION object cs and initialize it
with InitializeCriticalSection(&cs);
Then see code inserted in-line...

PaulH wrote:

I have a thread that listens on a message queue and populates a
std::deque with events from that message queue, but only holds the
latest 100.
In my main thread, I want to populate a listbox with the information
from that deque. So, it ends up being that one thread can add/remove
items from the deque while another thread is trying to iterate through
them. How can I make this thread-safe?

Thanks,
 PaulH

The code looks a bit like this:

std::deque<MESSAGE_TYPE> m_dequeMessages;

CMyClass::MessageThread()
{
  //...
  while (ReadMsgQueue(hMsgQueue, &msg,...))
  {


---> EnterCriticalSection(&cs);

    m_dequeMessages.push_back(msg);
    if(m_dequeMessages.size() > 100)
      m_dequeMessages.pop_front();


---> LeaveCriticalSection(&cs);

  }
  //...
}

CListCtrl c_MyList;

CDlgClass::PopulateList()
{


---> EnterCriticalSection(&cs);

  for (vector::iterator i = m_dequeMessages.begin(),
        i != m_vMessages.end()
        ++i)
  {
    c_MyList.InsertItem(0, i->Message);
  }


---> LeaveCriticalSection(&cs);

}


This will cause one thread to wait (at Enter...) if the other thread is
within the critical section.

--
Scott McPhillips [VC++ MVP]

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

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