root/win32/itpp-4.0.1/itpp/base/factory.h @ 35

/*!
 * \file
 * \brief Base class for class factories and memory allocation functions
 * \author Johan Bergman and Adam Piatyszek
 *
 * -------------------------------------------------------------------------
 *
 * IT++ - C++ library of mathematical, signal processing, speech processing,
 *        and communications classes and functions
 *
 * Copyright (C) 1995-2007  (see AUTHORS file for a list of contributors)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * -------------------------------------------------------------------------
 */

#ifndef FACTORY_H
#define FACTORY_H

#include <complex>
#include <itpp/base/binary.h>

namespace itpp {

  // Forward declarations
  template<class T> class Array;
  template<class Num_T> class Mat;
  template<class Num_T> class Vec;

  /*!
    \brief Base class for class factories

    A class factory (or virtual constructor) is a class that can create instances
    of another class. Factory is a base class for such factories. When declaring
    an Array, Vec or Mat, a factory can be passed as an (optional) constructor
    argument:
    \code
    // Declare a Vec<type> with size=10 and factory=DEFAULT_FACTORY
    Vec<type> a(10);

    // Declare a Vec<type> with size=10 and factory=f
    Factory f;
    Vec<type> b(10, f);
    \endcode

    By default, the factory (\c DEFAULT_FACTORY and \c f in the above examples)
    is not used at all! However, by overloading a help function called
    \e create_elements we can force Array/Vec/Mat to use the factory for element
    creation (instead of using the default constructor for the element type).

    \note It is the \e numeric elements that will be created by the factory,
    i.e. for an Array<Mat<T> >, the factory will be used for creating the Mat
    elements rather than the Array elements.

    Here is an example that (partly) defines a user-defined numeric type My_Type,
    a corresponding factory My_Factory and a corresponding help function
    create_elements<My_Type> that will be used by Array, Vec and Mat for element
    creation.
    \code
    class My_Type {
    public:
    // Default constructor
    My_Type() : data(0) {}
    // Constructor
    My_Type(int d) : data(d) {}
    .
    .
    .
    protected:
    int data;
    };

    class My_Factory : public Factory {
    public:
    // Constructor
    explicit My_Factory(int d) : init_data(d) {}
    // Destructor
    virtual ~My_Factory() {}
    // Create an n-length array of My_Type
    virtual void create(My_Type* &ptr, int n) const {ptr = new My_Type[n](init_data);}
    protected:
    int init_data;
    };

    // Create an n-length array of My_Type using My_Factory f
    template<>
    void create_elements<My_Type>(My_Type* &ptr, int n, const Factory &f)
    {
    if (const My_Factory *my_factory_ptr = dynamic_cast<const My_Factory*>(&f)) {
    // Yes, f seems to be a My_Factory. Now call the My_Factory::create method
    my_factory_ptr->create(ptr, n);
    }
    else {
    // No, f does not seem to be a My_Factory. As a fallback solution,
    // assume that f is DEFAULT_FACTORY and use the default constructor
    ptr = new My_Type[n];
    }
    }
    \endcode

    Now,
    \code
    // Declare a My_Factory for init_data = 123
    My_Factory my123_factory(123);

    // Declare a Vec<My_Type> with size 10 that uses My_Type() for element creation
    Vec<My_Type> v1(10);

    // Declare a Vec<My_Type> with size 10 that uses My_Type(123) for element creation
    Vec<My_Type> v1(10, my123_factory);
    \endcode

    For a more interesting example, see Fix_Factory.
  */
  class Factory {
  public:
    //! Default constructor
    Factory() {}
    //! Destructor
    virtual ~Factory() {}
  };

  //! Default (dummy) factory
  const Factory DEFAULT_FACTORY;


  //! Create an n-length array of T to be used as Array, Vec or Mat elements
  template<class T>
  void create_elements(T* &ptr, int n, const Factory &)
  {
    void *p = operator new(sizeof(T) * n);
    ptr = reinterpret_cast<T*>(p);
    for (int i = 0; i < n; i++) {
      new (ptr + i) T();
    }
  }


  //! Specialization for unsigned char data arrays (used in GF2Mat)
  template<>
  void create_elements<unsigned char>(unsigned char* &ptr, int n,
                                      const Factory &);
  //! Specialization for binary data arrays
  template<>
  void create_elements<bin>(bin* &ptr, int n, const Factory &);
  //! Specialization for short integer data arrays
  template<>
  void create_elements<short int>(short int* &ptr, int n, const Factory &);
  //! Specialization for integer data arrays
  template<>
  void create_elements<int>(int* &ptr, int n, const Factory &);
  //! Specialization for 16-byte aligned double data arrays
  template<>
  void create_elements<double>(double* &ptr, int n, const Factory &);
  //! Specialization for 16-byte aligned complex double data arrays
  template<>
  void create_elements<std::complex<double> >(std::complex<double>* &ptr, int n, const Factory &);


  //! Destroy an array of Array, Vec or Mat elements
  template<class T>
  void destroy_elements(T* &ptr, int n)
  {
    if (ptr) {
      for (int i = 0; i < n; ++i) {
        ptr[i].~T();
      }
      void *p = reinterpret_cast<void*>(ptr);
      operator delete(p);
      ptr = 0;
    }
  }

  //! Specialization for unsigned char data arrays (used in GF2Mat)
  template<>
  void destroy_elements<unsigned char>(unsigned char* &ptr, int n);
  //! Specialization for binary data arrays
  template<>
  void destroy_elements<bin>(bin* &ptr, int n);
  //! Specialization for short integer data arrays
  template<>
  void destroy_elements<short int>(short int* &ptr, int n);
  //! Specialization for integer data arrays
  template<>
  void destroy_elements<int>(int* &ptr, int n);
  //! Specialisation for 16-byte aligned double data arrays
  template<>
  void destroy_elements<double>(double* &ptr, int n);
  //! Specialisation for 16-byte aligned complex double data arrays
  template<>
  void destroy_elements<std::complex<double> >(std::complex<double>* &ptr,
                                               int n);


  //! Create an n-length array of Array<T> to be used as Array elements
  template<class T>
  void create_elements(Array<T>* &ptr, int n, const Factory &f)
  {
    void *p = operator new(sizeof(Array<T>) * n);
    ptr = reinterpret_cast<Array<T>*>(p);
    for (int i = 0; i < n; ++i) {
      new (ptr + i) Array<T>(f);
    }
  }

  //! Create an n-length array of Mat<T> to be used as Array elements
  template<class T>
  void create_elements(Mat<T>* &ptr, int n, const Factory &f)
  {
    void *p = operator new(sizeof(Mat<T>) * n);
    ptr = reinterpret_cast<Mat<T>*>(p);
    for (int i = 0; i < n; ++i) {
      new (ptr + i) Mat<T>(f);
    }
  }

  //! Create an n-length array of Vec<T> to be used as Array elements
  template<class T>
  void create_elements(Vec<T>* &ptr, int n, const Factory &f)
  {
    void *p = operator new(sizeof(Vec<T>) * n);
    ptr = reinterpret_cast<Vec<T>*>(p);
    for (int i = 0; i < n; ++i) {
      new (ptr + i) Vec<T>(f);
    }
  }

} // namespace itpp

#endif // #ifndef FACTORY_H