stl_iterator_base_types.h

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// Types used in iterator implementation -*- C++ -*-

// Copyright (C) 2001, 2002, 2004 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
// any later version.

// This library 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 library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
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// invalidate any other reasons why the executable file might be covered by
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/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 *
 * Copyright (c) 1996-1998
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file stl_iterator_base_types.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 *
 *  This file contains all of the general iterator-related utility types,
 *  such as iterator_traits and struct iterator.
 */

#ifndef _ITERATOR_BASE_TYPES_H
#define _ITERATOR_BASE_TYPES_H 1

//#pragma GCC system_header

namespace std
{
    //@{
    /**
     *  @defgroup iterator_tags Iterator Tags
     *  These are empty types, used to distinguish different iterators.  The
     *  distinction is not made by what they contain, but simply by what they
     *  are.  Different underlying algorithms can then be used based on the
     *  different operations supporetd by different iterator types.
     */
    ///  Marking input iterators.
    struct input_iterator_tag {};
    ///  Marking output iterators.
    struct output_iterator_tag {};
    /// Forward iterators support a superset of input iterator operations.
    struct forward_iterator_tag : public input_iterator_tag {};
    /// Bidirectional iterators support a superset of forward iterator
    /// operations.
    struct bidirectional_iterator_tag : public forward_iterator_tag {};
    /// Random-access iterators support a superset of bidirectional iterator
    /// operations.
    struct random_access_iterator_tag : public bidirectional_iterator_tag {};
    //@}


    /**
     *  @brief  Common %iterator class.
     *
     *  This class does nothing but define nested typedefs.  %Iterator classes
     *  can inherit from this class to save some work.  The typedefs are then
     *  used in specializations and overloading.
     *
     *  In particular, there are no default implementations of requirements
     *  such as @c operator++ and the like.  (How could there be?)
     */
    template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
        typename _Pointer = _Tp*, typename _Reference = _Tp&>
            struct iterator
            {
                /// One of the @link iterator_tags tag types@endlink.
                typedef _Category  iterator_category;
                /// The type "pointed to" by the iterator.
                typedef _Tp        value_type;
                /// Distance between iterators is represented as this type.
                typedef _Distance  difference_type;
                /// This type represents a pointer-to-value_type.
                typedef _Pointer   pointer;
                /// This type represents a reference-to-value_type.
                typedef _Reference reference;
            };

    /**
     *  This class does nothing but define nested typedefs.  The general
     *  version simply "forwards" the nested typedefs from the Iterator
     *  argument.  Specialized versions for pointers and pointers-to-const
     *  provide tighter, more correct semantics.
     */
    template<typename _Iterator>
        struct iterator_traits
        {
            typedef typename _Iterator::iterator_category iterator_category;
            typedef typename _Iterator::value_type        value_type;
            typedef typename _Iterator::difference_type   difference_type;
            typedef typename _Iterator::pointer           pointer;
            typedef typename _Iterator::reference         reference;
        };

    template<typename _Tp>
        struct iterator_traits<_Tp*>
        {
            typedef random_access_iterator_tag iterator_category;
            typedef _Tp                         value_type;
            typedef ptrdiff_t                   difference_type;
            typedef _Tp*                        pointer;
            typedef _Tp&                        reference;
        };

    template<typename _Tp>
        struct iterator_traits<const _Tp*>
        {
            typedef random_access_iterator_tag iterator_category;
            typedef _Tp                         value_type;
            typedef ptrdiff_t                   difference_type;
            typedef const _Tp*                  pointer;
            typedef const _Tp&                  reference;
        };

    /**
     *  @if maint
     *  This function is not a part of the C++ standard but is syntactic
     *  sugar for internal library use only.
     *  @endif
     */
    template<typename _Iter>
        inline typename iterator_traits<_Iter>::iterator_category
        __iterator_category(const _Iter&)
        { return typename iterator_traits<_Iter>::iterator_category(); }

} // namespace std

#endif /* _ITERATOR_BASE_TYPES_H */