//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//==============================================================================
// NOTICE: This file has been modified by Green Hills Software, Inc.  Such
// modifications are subject to copyright by Green Hills Software, Inc.  See the
// "Green Hills Software Modifications" section in the LICENSE.txt included with
// this distribution for more information.
//==============================================================================

#ifndef _LIBCPP___ALGORITHM_SHIFT_LEFT_H
#define _LIBCPP___ALGORITHM_SHIFT_LEFT_H

#include <__algorithm/move.h>
#include <__config>
#include <__iterator/iterator_traits.h>
#include <type_traits>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

#if defined(__ghs__)
  #pragma ghs start_cxx_lib_header
  #pragma ghs startdata
  #if defined(__ghs_max_pack_value)
    #pragma pack (push, __ghs_max_pack_value)
  #endif
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER > 17

template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY constexpr
_ForwardIterator
shift_left(_ForwardIterator __first, _ForwardIterator __last,
           typename iterator_traits<_ForwardIterator>::difference_type __n)
{
    if (__n == 0) {
        return __last;
    }

    _ForwardIterator __m = __first;
    if constexpr (__is_cpp17_random_access_iterator<_ForwardIterator>::value) {
        if (__n >= __last - __first) {
            return __first;
        }
        __m += __n;
    } else {
        for (; __n > 0; --__n) {
            if (__m == __last) {
                return __first;
            }
            ++__m;
        }
    }
    return _VSTD::move(__m, __last, __first);
}

#endif // _LIBCPP_STD_VER > 17

_LIBCPP_END_NAMESPACE_STD

#if defined(__ghs__)
  #if defined(__ghs_max_pack_value)
    #pragma pack(pop)
  #endif
  #pragma ghs enddata
  #pragma ghs end_cxx_lib_header
#endif

#endif // _LIBCPP___ALGORITHM_SHIFT_LEFT_H