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Semaphores

Posted on 1998-12-11
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Last Modified: 2013-11-20
I have an application where two CallBacks access a single
resource. I am told that I can use the initialize the Class
CSemaphore and then call CSingleLock::Lock at the beginning and CSingleLock::UnLock  at the end of both CallBacks. Is this true? How do I instantiate and use these functions.
IF this is the correct approach, can some one show me the
4 or 5 lines of code that initializes the CSemaphore,
and calls Lock and Unlock functions? Thanks.
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Question by:mparavas
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Accepted Solution

by:
Tommy Hui earned 100 total points
ID: 1326066
I wouldn't use a semaphore here. Instead, I would use a critical section. The idea is the same though.

First, you need to create a critical section that can be accessible from both callback functions. One possible implementation is a global instance.

CCriticalSection g_CS;

Then in your callbacks, you would do something like

void Callback1()
{
  // do stuff here

  // Get read to use shared resource
  g_CS.Lock();

  // Use resource

  // Free the resource
  g_CS.Unlock();
}

You would have the same general piece of code for the second callback.

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Author Comment

by:mparavas
ID: 1326067
Excellent idea. It worked great. Thanks a lot.
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