a question about multiplethread

[Siddhartha]

The easiest approach to restricting the number of threads that execute a piece of code to one is via Critical Sections.

• Critical Section Objects

One works with Critical Sections using Win APIs -

• InitializeCriticalSection
• EnterCriticalSection
• LeaveCriticalSection
• DeleteCriticalSection

• Sample: Using Critical Sections

So, in your case, the code would be something like this -

Creating and Initializing:

// A global object, or a globally accessible object (like static member)
CRITICAL_SECTION myCS;

// In the main thread
::InitializeCriticalSection (&myCS);

Using Critical Sections:

// Inside the worker thread

// At the point in code that needs to be protected
// And needs to be entered one thread at a time

::EnterCriticalSection (&myCS);

// The lines of code that need to be protected

::LeaveCriticalSection (&myCS);

Finally, Deleting:

// Again in the main thread, after the worker threads
// Have ended and the CS is not needed
::DeleteCriticalSection (&myCS);

Hope, you now have a clear idea of the way to proceed.