# AlgorithmSource

VTKExamples/Cxx/Developers/AlgorithmSource

### Description

This example demonstrates how to create a source that returns a custom class. To test that it is working, the class vtkTest1 simply stores a double named 'Value' that is instantiated to the value of 4.5. Example.cxx instantiates a vtkTestSource which produces a vtkTest1.

### Code

AlgorithmSource.cxx

    #include <vtkSmartPointer.h>

    #include "vtkTestAlgorithmSource.h"
    #include "vtkTest1.h"

    int main(int, char *[])
    {
      vtkTestAlgorithmSource* source = vtkTestAlgorithmSource::New();
      source->Update();

      vtkTest1* test = source->GetOutput();
      std::cout << test->GetValue() << std::endl;

      return EXIT_SUCCESS;
    }

vtkTest1.h

    #ifndef __vtkTest1_h
    #define __vtkTest1_h

    #include "vtkDataObject.h"

    class vtkTest1 : public vtkDataObject
    {
      public:
        static vtkTest1* New();
        vtkTypeMacro(vtkTest1,vtkDataObject);
        void PrintSelf( ostream& os, vtkIndent indent );

        vtkGetMacro(Value, double);

      protected:
        vtkTest1();
        ~vtkTest1();

      private:
        vtkTest1( const vtkTest1& ); // Not implemented.
        void operator = ( const vtkTest1& ); // Not implemented.

        double Value;
    };

    #endif

vtkTestAlgorithmSource.h

    #ifndef __vtkTestAlgorithmSource_h
    #define __vtkTestAlgorithmSource_h

    #include "vtkAlgorithm.h"

    class vtkDataSet;
    class vtkTest1;

    class vtkTestAlgorithmSource : public vtkAlgorithm
    {
    public:
      static vtkTestAlgorithmSource *New();
      vtkTypeMacro(vtkTestAlgorithmSource,vtkAlgorithm);
      void PrintSelf(ostream& os, vtkIndent indent);

      // Description:
      // Get the output data object for a port on this algorithm.
      vtkTest1* GetOutput();
      vtkTest1* GetOutput(int);
      virtual void SetOutput(vtkDataObject* d);

      // Description:
      // see vtkAlgorithm for details
      virtual int ProcessRequest(vtkInformation*,
                                 vtkInformationVector**,
                                 vtkInformationVector*);

    protected:
      vtkTestAlgorithmSource();
      ~vtkTestAlgorithmSource();

      // Description:
      // This is called by the superclass.
      // This is the method you should override.
      virtual int RequestDataObject(
        vtkInformation* request,
        vtkInformationVector** inputVector,
        vtkInformationVector* outputVector );

      // convenience method
      virtual int RequestInformation(
        vtkInformation* request,
        vtkInformationVector** inputVector,
        vtkInformationVector* outputVector );

      // Description:
      // This is called by the superclass.
      // This is the method you should override.
      virtual int RequestData(
        vtkInformation* request,
        vtkInformationVector** inputVector,
        vtkInformationVector* outputVector );

      // Description:
      // This is called by the superclass.
      // This is the method you should override.
      virtual int RequestUpdateExtent(
        vtkInformation*,
        vtkInformationVector**,
        vtkInformationVector* );

      virtual int FillOutputPortInformation( int port, vtkInformation* info );

    private:
      vtkTestAlgorithmSource( const vtkTestAlgorithmSource& ); // Not implemented.
      void operator = ( const vtkTestAlgorithmSource& );  // Not implemented.
    };

    #endif

vtkTest1.cxx

    #include "vtkTest1.h"

    #include "vtkObjectFactory.h"

    vtkStandardNewMacro(vtkTest1);

    vtkTest1::vtkTest1()
    {
      this->Value = 4.5;
    }

    vtkTest1::~vtkTest1()
    {

    }

    void vtkTest1::PrintSelf( ostream& os, vtkIndent indent )
    {
      this->Superclass::PrintSelf( os, indent );
    }

vtkTestAlgorithmSource.cxx

    #include "vtkTestAlgorithmSource.h"
    #include "vtkTest1.h"

    #include "vtkCommand.h"
    #include "vtkInformation.h"
    #include "vtkInformationVector.h"
    #include "vtkObjectFactory.h"
    #include "vtkStreamingDemandDrivenPipeline.h"

    vtkStandardNewMacro(vtkTestAlgorithmSource);

    //----------------------------------------------------------------------------
    vtkTestAlgorithmSource::vtkTestAlgorithmSource()
    {
      this->SetNumberOfInputPorts( 0 );
      this->SetNumberOfOutputPorts( 1 );
    }

    //----------------------------------------------------------------------------
    vtkTestAlgorithmSource::~vtkTestAlgorithmSource()
    {
    }

    //----------------------------------------------------------------------------
    void vtkTestAlgorithmSource::PrintSelf(ostream& os, vtkIndent indent)
    {
      this->Superclass::PrintSelf(os, indent);
    }

    //----------------------------------------------------------------------------
    vtkTest1* vtkTestAlgorithmSource::GetOutput()
    {
      return this->GetOutput(0);
    }

    //----------------------------------------------------------------------------
    vtkTest1* vtkTestAlgorithmSource::GetOutput(int port)
    {
      return vtkTest1::SafeDownCast(this->GetOutputDataObject(port));
    }

    //----------------------------------------------------------------------------
    void vtkTestAlgorithmSource::SetOutput(vtkDataObject* d)
    {
      this->GetExecutive()->SetOutputData(0, d);
    }

    //----------------------------------------------------------------------------
    int vtkTestAlgorithmSource::ProcessRequest(vtkInformation* request,
                                         vtkInformationVector** inputVector,
                                         vtkInformationVector* outputVector)
    {
      // Create an output object of the correct type.
      if(request->Has(vtkDemandDrivenPipeline::REQUEST_DATA_OBJECT()))
      {
        return this->RequestDataObject(request, inputVector, outputVector);
      }
      // generate the data
      if(request->Has(vtkDemandDrivenPipeline::REQUEST_DATA()))
      {
        return this->RequestData(request, inputVector, outputVector);
      }

      if(request->Has(vtkStreamingDemandDrivenPipeline::REQUEST_UPDATE_EXTENT()))
      {
        return this->RequestUpdateExtent(request, inputVector, outputVector);
      }

      // execute information
      if(request->Has(vtkDemandDrivenPipeline::REQUEST_INFORMATION()))
      {
        return this->RequestInformation(request, inputVector, outputVector);
      }

      return this->Superclass::ProcessRequest(request, inputVector, outputVector);
    }

    //----------------------------------------------------------------------------
    int vtkTestAlgorithmSource::FillOutputPortInformation(
        int vtkNotUsed(port), vtkInformation* info)
    {
      // now add our info
      info->Set(vtkDataObject::DATA_TYPE_NAME(), "vtkTest1");
      return 1;
    }

    //----------------------------------------------------------------------------
    int vtkTestAlgorithmSource::RequestDataObject(
                                            vtkInformation* vtkNotUsed(request),
        vtkInformationVector** vtkNotUsed(inputVector),
                                          vtkInformationVector* outputVector )
    {
      for ( int i = 0; i < this->GetNumberOfOutputPorts(); ++i )
      {
        vtkInformation* outInfo = outputVector->GetInformationObject( i );
        vtkTest1* output = vtkTest1::SafeDownCast(
                                                outInfo->Get( vtkDataObject::DATA_OBJECT() ) );
        if ( ! output )
        {
          output = vtkTest1::New();
          outInfo->Set( vtkDataObject::DATA_OBJECT(), output );
          output->FastDelete();
          this->GetOutputPortInformation( i )->Set(
                                          vtkDataObject::DATA_EXTENT_TYPE(), output->GetExtentType() );
        }
      }
      return 1;
    }

    //----------------------------------------------------------------------------
    int vtkTestAlgorithmSource::RequestInformation(
                                             vtkInformation* vtkNotUsed(request),
        vtkInformationVector** vtkNotUsed(inputVector),
                                          vtkInformationVector* vtkNotUsed(outputVector))
    {
      // do nothing let subclasses handle it
      return 1;
    }

    //----------------------------------------------------------------------------
    int vtkTestAlgorithmSource::RequestUpdateExtent(
                                              vtkInformation* vtkNotUsed(request),
        vtkInformationVector** inputVector,
        vtkInformationVector* vtkNotUsed(outputVector))
    {
      int numInputPorts = this->GetNumberOfInputPorts();
      for (int i=0; i<numInputPorts; i++)
      {
        int numInputConnections = this->GetNumberOfInputConnections(i);
        for (int j=0; j<numInputConnections; j++)
        {
          vtkInformation* inputInfo = inputVector[i]->GetInformationObject(j);
          inputInfo->Set(vtkStreamingDemandDrivenPipeline::EXACT_EXTENT(), 1);
        }
      }
      return 1;
    }

    //----------------------------------------------------------------------------
    // This is the superclasses style of Execute method.  Convert it into
    // an imaging style Execute method.
    int vtkTestAlgorithmSource::RequestData(
                                      vtkInformation* vtkNotUsed(request),
        vtkInformationVector** vtkNotUsed( inputVector ),
                                           vtkInformationVector* vtkNotUsed(outputVector) )
    {
      // do nothing let subclasses handle it
      return 1;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(AlgorithmSource)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(AlgorithmSource MACOSX_BUNDLE AlgorithmSource.cxx  vtkTest1.cxx vtkTestAlgorithmSource.cxx)

    target_link_libraries(AlgorithmSource ${VTK_LIBRARIES})

### Download and Build AlgorithmSource

Click here to download AlgorithmSource and its CMakeLists.txt file. Once the tarball AlgorithmSource.tar has been downloaded and extracted,

    cd AlgorithmSource/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./AlgorithmSource

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.