ExampleSharedPtr.cpp

Example for SharedPointer usage

Author

woelk

/* 
This file is part of the BIAS library (Basic ImageAlgorithmS).

Copyright (C) 2003-2009    (see file CONTACT for details)
  Multimediale Systeme der Informationsverarbeitung
  Institut fuer Informatik
  Christian-Albrechts-Universitaet Kiel


BIAS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

BIAS 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with BIAS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/**
   @example ExampleSharedPtr.cpp
   @relates SharedPtr
   @brief Example for SharedPointer usage
   @ingroup g_examples
   @author woelk   
*/

#include <Base/Common/SharedPtr.hh>

#include <iostream>
#include <vector>
#include <string>

using namespace BIAS;
using namespace std;

/** \cond POORLY_NAMED_EXAMPLE_CLASSES **/
/* some base class */
class foo {
public:
  virtual ~foo() {};
  int i;
  double d;
};

std::ostream& operator<<(std::ostream& os, const foo& arg)
{ os << arg.i<<"  "<<arg.d; return os; }

/// some derive class
class uta : public foo {
public:
  virtual ~uta() {};
  string name;
};

std::ostream& operator<<(std::ostream& os, const uta& arg)
{ os << arg.i<<"  "<<arg.d<<"  "<<arg.name; return os; }

/** \endcond **/

int main(int argc, char *argv[])
{
  /// initialize the shared ptr
  SharedPtr<foo> p_foo = SharedPtr<foo>(new foo);

  /// check the reference count
  cout << "reference count of p_foo: "<<RefCount(p_foo)<<endl;

  // assign values
  p_foo->i = 5;
  (*p_foo).d = 3.1415;

  cout << "content of p_foo: "<<*p_foo<<endl;

  /// copy the pointer
  SharedPtr<foo> p_foo2 = p_foo;
  // thest for NULL
  if (p_foo2){
    cout << "simple test for NULL pointer : (p_foo2) \n"
         << "content of p_foo2: "<<*p_foo2<<endl;
  }

  /// the reference count should be 2: p_foo and p_foo2 both point to the
  /// same object
  // comparison
  if (p_foo == p_foo2)
    cout << "p_foo and p_foo2 point ot the same object: reference count "
       <<RefCount(p_foo)<<" and "<<RefCount(p_foo2)<<endl;
  else 
    cout << "this cannot happen\n";
  
  // assigning NULL to p_foo2 let the reference count of p_foo drop 
  p_foo2 = SharedPtr<foo>(NULL);
  cout << "re-assigned p_foo2: reference count "<<RefCount(p_foo)<<endl;

  // a pointer to a const foo
  SharedPtr<const foo> pc_foo;

  /// casting works slighty different
  pc_foo = ConstCast<const foo>(p_foo);
  
  SharedPtr<uta> p_uta(new uta);
  p_uta->i=2;
  p_uta->d=2.0*3.1415;
  p_uta->name="diogenes";
  
  /// dynamic casting works slighty different 
  p_foo2 = DynamicCast<foo>(p_uta);
  if (p_foo2 == p_uta)
    cout << "p_uta and p_foo2 point to the same object: ref count "
         <<RefCount(p_uta)<<endl
         << "  content of p_foo2: "<<*p_foo2<<endl;
  else
    cerr << "this will not happen\n";

  SharedPtr<uta> p_uta2 = DynamicCast<uta>(p_foo2);
  if (p_uta2)
    cout << "*p_uta2: "<<*p_uta2<<endl;

  // no call to delete necessary, the object is automatically deleted when
  // the reference count drops to zero
  return 0;
}