CStream class

Pipelines v2.0

Member variables, Member functions

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Description

The CStream class is the base class of both the CInStream and COutStream classes.

It is through these class objects that the StageManager coordinates the flow of records into and out of your stage. However, the CInstream and COutStream classes themselves do not expose any of their read, write or connect member functions to you; they only expose that part of their interface to the CStageManager; which means that you are shielded from the internal complexity of how your streams are actually connected and how input and output records flow through them. The limited set of functions that these classes’ do expose; are those that they inherit from their base class CStream and these are shown below.

The CInstream and COutStream classes are not included in this API documentation as they do not provide any information that is of use to a stage designer.

Definition

The following class definition is an edited version; it details only those members which are accessible and of use to you. In addition; any examples that may be shown are only intended as a demonstration of how certain functions might be used, they do not represent best practice nor do they take into account the scope and de-allocation of class objects.

// The CStream class is the base class from which the CInStream and COutStream classes are derived.
 
class CStream 
{
 public:
 
 bool IsConnected( void ) const;
 bool IsDisConnected( void ) const;
};

Member variables

None.

Member functions

bool CStream::IsConnected( void ) const;

●

Purpose

Use IsConnected() to determine if a stream is connected.

●

Parameters

●

void

●

Returns

●	bool true if the stream is connected, otherwise; false which indicates that the stream is disconnected.

●

Messages

None

●

Usage

To determine if a stream is connected:
 
DWORD CMyStage::Go( void )
{
 // Access the manager.
 CStageManager *pManager = Manager();
 // Access my stage.
 CStage *pStage = pManager->GetStage( *this );
 
  ...
 
 // Loop through my input streams and read a record from each
 // connected stream.
 
 CString szRecord;
 DWORD dwMaxInStream = pStage->MaxInStream();
 
 for( DWORD dwInStream = 0; dwInStream < dwMaxInStream; ++dwInStream )
 {
 CInStream *pInStream = pStage->GetInStream( dwInStream );
 if( pInStream->IsConnected() )
 {
 // Read a record from the input stream.
 pManager->ReadRecord( *this, dwInStream, &szRecord ) )
 
 ...
 }
 }
 
 ...
 
 return( _RC_SUCCESS_ )
}

bool CStream::IsDisConnected( void ) const;

●

Purpose

Use IsDisConnected() to determine if a stream is disconnected.

●

Parameters

●

void

●

Returns

●	bool true if the stream is disconnected, otherwise; false which indicates that the stream is connected.

●

Messages

None

●

Usage

To determine if a stream is disconnected:
 
DWORD CMyStage::Go( void )
{
 // Access the manager.
 CStageManager *pManager = Manager();
 // Access my stage.
 CStage *pStage = pManager->GetStage( *this );
 
 // Get a pointer to my primary output stream.
 COutStream *pPriOutStream = pStage->GetOutStream( 0 );
 
 ...
 
 // My stage reads each set of 20 records from its primary input stream,
 // and writes an output record which details the accumulated/running total
 // of the number of input records read so far.
 
 // Record buffer.
 CString szRecord;
 
 DWORD dwAccumulator = 0;
 DWORD dwTotal = 0;
 
 while( true )
 {
 // If my primary output stream is disconnected; then there is no need
 // to continue reading records from my primary input stream.
 
 if( pPriOutStream->IsDisConnected() )
 break;
 
 // Read a record from my primary input stream.
 if( !pManager->ReadRecord( *this, 0, &szRecord ) ) 
 {
 // This is the end-of-file on my primary input stream.
  break;
 }
 
 if( dwAccumulator == 20 )
 {
 szRecord.Format( “%ld”, dwTotal );
 
 // Write the record to my primary output stream.
 if( !pManager->WriteRecord( *this, 0, &szRecord ) )
 {
 // This is the end-of-file on my primary output stream.
 break;
 }
 
 dwAccumulator = 0;
 }
 
  ++dwTotal;
 }
 
 return( _RC_SUCCESS_ );
}