CAMThread Class
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This is an abstract class, a worker thread class that provides creation, synchronization, and communication with a worker thread. The worker thread can be accessed from several client threads. The class provides member functions to create the thread, pass commands to it, and wait for it to exit.
Use a CCritSec object to ensure that only one thread can make a request at a time. Use two CAMEvent objects: one to signal to the worker that a request is outstanding, and the other to signal to the client thread that the request has been completed. A nonblocking CAMThread::CheckRequest member function allows the worker thread to check for new requests while working asynchronously.
Derive from this class to provide your own thread member function. You might also want to provide type-safe signaling member functions that package parameters and return values using the CAMThread::CallWorker member function.
Thread creation is independent of object creation. Create a member variable derived from CAMThread, and then use the member functions to start and stop the thread when needed.
Data Members
| Member | Description |
|---|---|
| m_AccessLock | Critical section object that locks access by client threads. |
| m_WorkerLock | Critical section object that locks access to shared objects. |
Member Functions
| Member function | Description |
|---|---|
| CallWorker | Makes a request to the worker thread. |
| CAMThread | Constructs a CAMThread object. |
| CheckRequest | Determines if there is an outstanding request. This is a nonblocking member function. |
| Close | Blocks until the thread has exited and released its resources. |
| Create | Starts the thread running. |
| GetRequest | Blocks until the next request is made and then returns a DWORD value. |
| GetRequestHandle | Retrieves an event handle. |
| GetRequestParam | Retrieves the latest request. |
| InitialThreadProc | Retrieves a this pointer. Carry out this member function before calling the CAMThread::ThreadProc member function. |
| Reply | Retrieves a DWORD value to the requesting thread and releases it, signaling completion of the request. |
| ThreadExists | Determines whether a thread exists or has exited. |
| ThreadProc | Indicates a pure virtual member function that is called on the worker thread. |
Requirements
DirectShow applications and DirectShow filters have different include file and link library requirements. See Setting Up the Build Environment for more information.
OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
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Last updated on Wednesday, April 13, 2005
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