CSource Class

This class and its corresponding class, CSourceStream, simplify the construction of source filters that produce continuous streams of data comparable to the way the CTransformFilter class assists in the creation of transform filters.

The CSource class provides a wrapper for the CBaseFilter class that performs the pin management and works with the CSourceStream class to provide the pins.

To use the CSource class to build a filter:

• Derive your filter-level class from the CSource class. Provide a CreateInstance member function in it to create a new object of the class.
• Provide a means of adding objects that are derived from the CSourceStream class to support the output pins during construction of the class. You can either create them yourself during construction or provide the developer with a means of creating them later.

For an example of using the CSource class, see the Ball sample in the \Samples\DS\Ball directory of the Microsoft® DirectShow™ SDK Software Development Kit (SDK).

This class does not help build an asynchronous file reader source filter, which requires support of an IAsyncReader interface and a downstream parser filter that supports the CPullPin class.

Protected Data Members

Name	Description
m_cStateLock	Locks this data member to serialize access to the filter state.
m_iPins	Number of pins on this filter; updated by the CSource::AddPin and CSource::RemovePin member functions.
m_paStreams	Array of streams associated with this filter.

Member Functions

Name	Description
AddPin	Adds a pin to the source filter.
CSource	Constructs a CSource object.
FindPinNumber	Retrieves the number of the pin through the IPin parameter.
GetPin	Returns a pointer to a specified pin.
GetPinCount	Gets the number of pins contained by the filter.
pStateLock	Returns a pointer to the filter-critical section.
RemovePin	Removes a pin from the source filter.

Implemented IBaseFilter Methods

Name	Description
FindPin	Retrieves a pointer to the pin with the specified identifier.

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CSource::AddPin

CSource Class

Adds a pin to the source filter.

HRESULT AddPin(
  CSourceStream * pStream
  );

Parameters

pStream

Pointer to the CSourceStream object associated with the pin.

Return Values

Returns S_OK if successful, or E_OUTOFMEMORY if no memory is available.

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CSource::CSource

CSource Class

Initializes the CSource object.

CSource(
  TCHAR *pName,
  LPUNKNOWN lpunk,
  CLSID clsid
  );

Parameters

pName

Debugging name of this object.

lpunk

Controlling IUnknown passed to the derived class's CreateInstance function.

clsid

Class identifier of the filters.

Return Values

No return value.

Remarks

The derived class could create the pins here, unless it provides a means for the developer to do this.

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CSource::FindPinNumber

CSource Class

Retrieves the number of the pin supporting a given IPin interface.

int FindPinNumber(
  IPin *iPin
  );

Parameters

iPin

IPin interface of the pin to retrieve.

Return Values

Returns the pin number or –1 if no matching pin number is found.

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CSource::GetPin

CSource Class

Returns a pointer to the specified pin.

CBasePin *GetPin(
  int n
  );

Parameters

n

Pin number of the requested pin.

Return Values

Returns the pointer to the pin or NULL if the index is out of range.

Remarks

This member function is specified in CBaseFilter and is implemented here. Note that this pin interface will not have been reference counted when obtained.

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CSource::GetPinCount

CSource Class

Retrieves the number of pins contained by the filter.

int GetPinCount(void);

Return Values

Returns the pin count.

Remarks

This member function is specified in CBaseFilter and is implemented here.

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CSource::pStateLock

CSource Class

Retrieves a pointer to the filter-critical section.

CCritSec* pStateLock(void);

Return Values

Returns the critical section.

Remarks

Locking consists of holding the filter-critical section by calling the pStateLock member function and using the returned object to serialize access to functions. Typically, this lock can be held by a function when the worker thread might want to hold it. Therefore, to access a shared state from the worker thread, add another critical-section object. The exception occurs during the processing loop of the thread when it is safe to retrieve the filter-critical section from within CSourceStream::FillBuffer.

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CSource::RemovePin

CSource Class

Removes a pin from the source filter.

HRESULT RemovePin(
  CSourceStream * pStream
  );

Parameters

pStream

CSourceStream object associated with the pin.

Return Values

Returns S_OK if successful or S_FALSE if unsuccessful.

Remarks

The pStream parameter is not deleted. This member function adjusts pin locations in the m_paStreams array.

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