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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