// Copyright Epic Games, Inc. All Rights Reserved.

#include "Common.ush"

template<typename T>
struct TDefaultCompare
{
	int Compare(T a, T b)
	{
		return int(a > b) - int(a < b);
	}
};

// BufferCount must be a power of 2
template<typename TBuffer, typename T, typename TCompare>
T LowerBound(TBuffer SearchBuffer, uint BufferOffset, uint BufferCount, T Key)
{
	TCompare Comp = (TCompare)0;
	uint Index = BufferOffset;
	uint Width = BufferCount >> 1;
	
	while (Width > 0)
	{
		Index += Comp.Compare(Key, SearchBuffer[Index + Width]) < 0 ? 0 : Width;
		Width = Width >> 1;
	}
	
	return Index;
}

// BufferCount must be a power of 2
template<typename TBuffer, typename T, typename TCompare>
bool BinarySearch(TBuffer SearchBuffer, uint BufferOffset, uint BufferCount, T Key, inout uint OutIndex)
{
	if (BufferCount == 0)
	{
		return false;
	}
	OutIndex = LowerBound<TBuffer, T, TCompare>(SearchBuffer, BufferOffset, BufferCount, Key);
	return SearchBuffer[OutIndex] == Key;
}

// BufferCount must be a power of 2
template<typename TBuffer, typename T, typename TCompare>
bool BinarySearch(TBuffer SearchBuffer, uint BufferOffset, uint BufferCount, T Key)
{
	uint Index;
	return BinarySearch<TBuffer, T, TCompare>(SearchBuffer, BufferOffset, BufferCount, Key, Index);
}

// BufferCount must be a power of 2
template<typename TBuffer, typename T>
bool BinarySearch(TBuffer SearchBuffer, uint BufferOffset, uint BufferCount, T Key, inout uint OutIndex)
{
	return BinarySearch< TBuffer, T, TDefaultCompare<T> >(SearchBuffer, BufferOffset, BufferCount, Key, OutIndex);
}

// BufferCount must be a power of 2
template<typename TBuffer, typename T>
bool BinarySearch(TBuffer SearchBuffer, uint BufferOffset, uint BufferCount, T Key)
{
	uint Index;
	return BinarySearch<TBuffer, T>(SearchBuffer, BufferOffset, BufferCount, Key, Index);
}