/* IBM_PROLOG_BEGIN_TAG                                                   */
/* This is an automatically generated prolog.                             */
/*                                                                        */
/* $Source: import/chips/p9/procedures/ppe/include/std/util/impl/iterator.h $ */
/*                                                                        */
/* OpenPOWER HCODE Project                                                */
/*                                                                        */
/* COPYRIGHT 2012,2017                                                    */
/* [+] International Business Machines Corp.                              */
/*                                                                        */
/*                                                                        */
/* Licensed under the Apache License, Version 2.0 (the "License");        */
/* you may not use this file except in compliance with the License.       */
/* You may obtain a copy of the License at                                */
/*                                                                        */
/*     http://www.apache.org/licenses/LICENSE-2.0                         */
/*                                                                        */
/* Unless required by applicable law or agreed to in writing, software    */
/* distributed under the License is distributed on an "AS IS" BASIS,      */
/* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or        */
/* implied. See the License for the specific language governing           */
/* permissions and limitations under the License.                         */
/*                                                                        */
/* IBM_PROLOG_END_TAG                                                     */

#ifndef __UTIL_IMPL_ITERATOR_H
#define __UTIL_IMPL_ITERATOR_H

/** @file iterator.h
 *
 *  Contains the internal implementation details of the stl <iterator> header.
 */

#include <util/traits/has_plusequals.H>
#include <util/traits/has_minus.H>

namespace Util
{
namespace __Util_Iterator_Impl
{

/**
 *  Template definition of an iterator advance functor.
 */
template <typename InputIterator, typename Distance,
          bool HasPlusEquals> struct AdvanceImpl;

/**
 *  Template specialization of the advance functor for iterators
 *  which do not support random access.
 */
template <typename InputIterator, typename Distance>
struct AdvanceImpl<InputIterator, Distance, false>
{
    static void advance(InputIterator& i, Distance n)
    {
        while(n--)
        {
            ++i;
        }
    }
};

/**
 *  Template specialization of the advance functor for iterators
 *  which do support random access.
 */
template <typename RandomIterator, typename Distance>
struct AdvanceImpl<RandomIterator, Distance, true>
{
    static void advance(RandomIterator& i, Distance n)
    {
        i += n;
    }
};

/**
 *  Template wrapper function for the iterator advance.
 *
 *  Uses the existence of a += operator on the iterator to determine
 *  if the random-access or non-random-access version should be used.
 */
template <typename InputIterator, typename Distance>
void advance(InputIterator& i, Distance n)
{
    AdvanceImpl<InputIterator, Distance,
                Util::Traits::has_plusequals<InputIterator, Distance,
                InputIterator>::value
                >::advance(i, n);
}

/**
 *  Template definition of an iterator distance functor.
 */
template <typename InputIterator, typename Distance,
          bool HasMinus> struct DistanceImpl;

/**
 *  Template specialization of the distance functor for iterators
 *  which do not support random access.
 */
template <typename InputIterator, typename Distance>
struct DistanceImpl<InputIterator, Distance, false>
{
    static Distance distance(InputIterator& first,
                             InputIterator& last)
    {
        Distance i = 0;

        while (first != last)
        {
            ++i;
            ++first;
        }

        return i;
    }
};

/**
 *  Template specialization of the distance functor for iterators
 *  which do support random access.
 */
template <typename RandomIterator, typename Distance>
struct DistanceImpl<RandomIterator, Distance, true>
{
    static Distance distance(RandomIterator& first,
                             RandomIterator& last)
    {
        return last - first;
    }
};

/**
 *  Template wrapper function for the iterator distance.
 *
 *  Uses the existence of a - operator on the iterator to determine
 *  if the random-access or non-random-access version should be used.
 */
template <typename InputIterator, typename Distance>
Distance distance(InputIterator& first,
                  InputIterator& last)
{
    return DistanceImpl<InputIterator, Distance,
           Util::Traits::has_minus<InputIterator, InputIterator,
           Distance>::value
           >::distance(first, last);
}

};
};

#endif
