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// Copyright (c) 2008-2020 NVIDIA Corporation. All rights reserved.
// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.

#pragma once


namespace nv
{

namespace cloth
{

// acts as a poor mans random access iterator
template <typename T4f, typename BaseIterator>
class LerpIterator
{

	LerpIterator& operator = (const LerpIterator&); // not implemented

  public:
	LerpIterator(BaseIterator start, BaseIterator target, float alpha)
	: mAlpha(simd4f(alpha)), mStart(start), mTarget(target)
	{
	}

	// return the interpolated point at a given index
	inline T4f operator[](size_t index) const
	{
		return mStart[index] + (mTarget[index] - mStart[index]) * mAlpha;
	}

	inline T4f operator*() const
	{
		return (*this)[0];
	}

	// prefix increment only
	inline LerpIterator& operator ++ ()
	{
		++mStart;
		++mTarget;
		return *this;
	}

  private:
	// interpolation parameter
	const T4f mAlpha;

	BaseIterator mStart;
	BaseIterator mTarget;
};

template <typename T4f, size_t Stride>
class UnalignedIterator
{

	UnalignedIterator& operator = (const UnalignedIterator&); // not implemented

  public:
	UnalignedIterator(const float* pointer) : mPointer(pointer)
	{
	}

	inline T4f operator[](size_t index) const
	{
		return load(mPointer + index * Stride);
	}

	inline T4f operator*() const
	{
		return (*this)[0];
	}

	// prefix increment only
	inline UnalignedIterator& operator ++ ()
	{
		mPointer += Stride;
		return *this;
	}

  private:
	const float* mPointer;
};

// acts as an iterator but returns a constant
template <typename T4f>
class ConstantIterator
{
  public:
	ConstantIterator(const T4f& value) : mValue(value)
	{
	}

	inline T4f operator*() const
	{
		return mValue;
	}

	inline ConstantIterator& operator ++ ()
	{
		return *this;
	}

  private:
	ConstantIterator& operator = (const ConstantIterator&);
	const T4f mValue;
};

// wraps an iterator with constant scale and bias
template <typename T4f, typename BaseIterator>
class ScaleBiasIterator
{
  public:
	ScaleBiasIterator(BaseIterator base, const T4f& scale, const T4f& bias)
	: mScale(scale), mBias(bias), mBaseIterator(base)
	{
	}

	inline T4f operator*() const
	{
		return (*mBaseIterator) * mScale + mBias;
	}

	inline ScaleBiasIterator& operator ++ ()
	{
		++mBaseIterator;
		return *this;
	}

  private:
	ScaleBiasIterator& operator = (const ScaleBiasIterator&);

	const T4f mScale;
	const T4f mBias;

	BaseIterator mBaseIterator;
};

} // namespace cloth

} // namespace nv