// Copyright (c) 1997
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel).  All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL$
// $Id$
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Lutz Kettner  <kettner@inf.ethz.ch>

#ifndef CGAL_IO_ISTREAM_ITERATOR_H
#define CGAL_IO_ISTREAM_ITERATOR_H

#include <CGAL/circulator.h>

namespace CGAL {

/*!
\ingroup PkgStreamSupportRef

The class `Istream_iterator` is an input iterator adaptor for the
input stream class `Stream` and value type `T`. It is particularly
useful for classes that are similar but not compatible to `std::istream`.

\cgalModels{InputIterator}
*/
template <class T, class Stream>
class Istream_iterator
{
protected:
  Stream* stream;
  T value;

  void read()
  {
    if(stream)
    {
      if(*stream)
      {
        *stream >> value;
        if(! *stream)
          stream = 0;
      }
      else
      {
        stream = 0;
      }
    }
  }

public:
  typedef T                           value_type;
  typedef const T&                    reference;
  typedef const T&                    const_reference;
  typedef const T*                    pointer;
  typedef const T*                    const_pointer;
  typedef std::size_t                 size_type;
  typedef std::ptrdiff_t              difference_type;
  typedef std::input_iterator_tag     iterator_category;
  typedef Istream_iterator<T,Stream>  Self;

  /// \name Creation
  /// @{

  /*!
  creates an end-of-stream iterator.
  This is a past-the-end iterator, and it is useful
  when constructing a range.
  */
  Istream_iterator() : stream(0) {}

  /*!
  creates an input iterator reading from `s`.
  When `s` reaches end of stream,
  this iterator will compare equal to an end-of-stream iterator
  created using the default constructor.
  */
  Istream_iterator(Stream& s) : stream(&s) { read(); }

  /// @}

  bool operator==( const Self& i) const { return stream == i.stream; }
  bool operator!=( const Self& i) const { return stream != i.stream; }

  reference operator*()  const { return value; }
#ifdef  CGAL_ARROW_OPERATOR
  pointer operator->() const { return &(operator*()); }
#endif
  Self& operator++()
  {
    read();
    return *this;
  }

  Self operator++(int)
  {
    Self tmp = *this;
    read();
    return tmp;
  }
};

} // namespace CGAL

#endif // CGAL_IO_ISTREAM_ITERATOR_H