Rotate.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "uLang/Common/Templates/Storage.h" // for Swap()
#include "uLang/Common/Common.h"
 
// nb: this was copied over from Core until uLang can properly depend on Core.
 
namespace uLang
{
namespace AlgoImpl
{
    template <typename T>
    size_t RotateInternal(T* First, size_t Num, size_t Count)
    {
        if (Count == 0)
        {
            return Num;
        }
 
        if (Count >= Num)
        {
            return 0;
        }
 
        T* Iter = First;
        T* Mid  = First + Count;
        T* End  = First + Num;
 
        T* OldMid = Mid;
        for (;;)
        {
            Swap(*Iter++, *Mid++);
            if (Mid == End)
            {
                if (Iter == OldMid)
                {
                    return Num - Count;
                }
 
                Mid = OldMid;
            }
            else if (Iter == OldMid)
            {
                OldMid = Mid;
            }
        }
    }
}
 
namespace Algo
{
    template <typename RangeType>
    ULANG_FORCEINLINE size_t Rotate(RangeType&& Range, size_t Count)
    {
        return AlgoImpl::RotateInternal(ULangGetData(Range), ULangGetNum(Range), Count);
    }
}
}