FindSequence.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Algo/Impl/RangePointerType.h"
 
namespace AlgoImpl
{
    template<typename WhereType, typename WhatType>
    constexpr WhereType* FindSequence(WhereType* First, WhereType* Last, WhatType* WhatFirst, WhatType* WhatLast)
    {
        for (; ; ++First)
        {
            WhereType* It = First;
            for (WhatType* WhatIt = WhatFirst; ; ++It, ++WhatIt)
            {
                if (WhatIt == WhatLast)
                {
                    return First;
                }
                if (It == Last)
                {
                    return nullptr;
                }
                if (!(*It == *WhatIt))
                {
                    break;
                }
            }
        }
    }
}
 
namespace Algo
{
 
    /*
    * Searches for the first occurrence of a sequence of elements in another sequence.
    *
    * @param Where The range to search
    * @param What The sequence to search for.
    *
    * @return A pointer to the first occurrence of the "What" sequence in "Where" sequence, or nullptr if not found.
    */
    template<typename RangeWhereType, typename RangeWhatType>
    [[nodiscard]] auto FindSequence(const RangeWhereType& Where, const RangeWhatType& What)
        -> decltype( AlgoImpl::FindSequence( GetData(Where), GetData(Where) + GetNum(Where), GetData(What), GetData(What) + GetNum(What)) )
    {
        if (GetNum(What) > GetNum(Where))
        {
            return nullptr;
        }
        else
        {
            return AlgoImpl::FindSequence(
                GetData(Where), GetData(Where) + GetNum(Where),
                GetData(What), GetData(What) + GetNum(What));
        }
    }
 
}