vnl_matrix_ref.h

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#ifndef vnl_matrix_ref_h_
#define vnl_matrix_ref_h_

// This is vxl/vnl/vnl_matrix_ref.h

//:
// \file
// \brief vnl_matrix reference to user-supplied storage.
//
// \author Andrew W. Fitzgibbon, Oxford RRG, 04 Aug 96


//
//Modifications:
//  Documentation updated by Ian Scott 12 Mar 2000
//
//-----------------------------------------------------------------------------

#include <vcl_new.h>
#include <vnl/vnl_matrix.h>

//: vnl_matrix reference to user-supplied storage
//    vnl_matrix_ref is a vnl_matrix for which the data space has been
//    supplied externally.  This is useful for two main tasks:
//    (a) Treating some row-based "C" matrix as a vnl_matrix in order to
//    perform vnl_matrix operations on it.
//    (b) Declaring a vnl_matrix that uses stack-based storage for the
//    matrix (See MatrixFixed).  Note however that the rows are still allocated
//    on the heap.  See MatrixFixed for a fully stack-based solution.
//
//    This is a dangerous class.  I believe that I've covered all the bases, but
//    it's really only intended for interfacing with the Fortran routines.
//
//    The big warning is that returning a vnl_matrix_ref pointer will free non-heap
//    memory if deleted through a vnl_matrix pointer.  This should be
//    very difficult though, as vnl_matrix_ref objects may not be constructed using
//    operator new, and are therefore unlikely to be the unwitting subject
//    of an operator delete.
template <class T>
class vnl_matrix_ref : public vnl_matrix<T> {
  typedef vnl_matrix<T> Base;

public:
  // Constructors/Destructors--------------------------------------------------
  vnl_matrix_ref(int m, int n, T *datablck) {
    Base::data = vnl_c_vector<T>::allocate_Tptr(m);
    for(int i = 0; i < m; ++i)
      Base::data[i] = datablck + i * n;
    Base::num_rows = m;
    Base::num_cols = n;
  }
  ~vnl_matrix_ref() {
    Base::data[0] = 0; // Prevent base dtor from releasing our memory
  }

private:
  // Private operator new because deleting a pointer to
  // one of these through a baseclass pointer will attempt
  // to free this in-class memory.
  // Therefore disallow newing of these -- if you're paying for
  // one malloc, you can afford three.
// fsm: This was wrong for two reasons:
//  1. operator new may not return a null pointer.
//  2. it should be enabled for compilers that need it,
//     not disabled for compilers that don't need it.
//#if !defined(VCL_GCC_295)
//  void* operator new(size_t) { return 0; }
//#endif


  //: Resizing is disallowed
  bool resize (unsigned int, unsigned int) { return 0; }


  //: Copy constructor is disallowed
  // because it would create a non-const alias to the Matrix
  vnl_matrix_ref(vnl_matrix<T> const &) {}


  // You can't assign one of these from a matrix, cos' you don't have any space
  vnl_matrix_ref(vnl_matrix_ref<T> const &) {}
  vnl_matrix_ref<T>& operator=(vnl_matrix<T> const &) { return *this; }
};

#endif // vnl_matrix_ref_h_

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