/// <summary>
/// SIMD optimized bulk implementation of <see cref="IPixel.PackFromVector4(Vector4)"/>
/// that works only with `count` divisible by <see cref="Vector{UInt32}.Count"/>.
/// </summary>
/// <param name="sourceColors">The <see cref="BufferPointer{T}"/> to the source colors.</param>
/// <param name="destVectors">The <see cref="BufferPointer{T}"/> to the dstination vectors.</param>
/// <param name="count">The number of pixels to convert.</param>
/// <remarks>
/// Implementation adapted from:
/// <see>
/// <cref>http://stackoverflow.com/a/5362789</cref>
/// </see>
/// TODO: We can replace this implementation in the future using new Vector API-s:
/// <see>
/// <cref>https://github.com/dotnet/corefx/issues/15957</cref>
/// </see>
/// </remarks>
internal static unsafe void ToVector4SimdAligned(
BufferPointer <Color> sourceColors,
BufferPointer <Vector4> destVectors,
int count)
{
int vecSize = Vector <uint> .Count;
DebugGuard.IsTrue(
count % vecSize == 0,
nameof(count),
"Argument 'count' should divisible by Vector<uint>.Count!");
Vector <float> bVec = new Vector <float>(256.0f / 255.0f);
Vector <float> magicFloat = new Vector <float>(32768.0f);
Vector <uint> magicInt = new Vector <uint>(1191182336); // reinterpreded value of 32768.0f
Vector <uint> mask = new Vector <uint>(255);
int unpackedRawCount = count * 4;
uint *src = (uint *)sourceColors.PointerAtOffset;
uint *srcEnd = src + count;
using (PinnedBuffer <uint> tempBuf = new PinnedBuffer <uint>(
unpackedRawCount + Vector <uint> .Count))
{
uint * tPtr = (uint *)tempBuf.Pointer;
uint[] temp = tempBuf.Array;
float[] fTemp = Unsafe.As <float[]>(temp);
UnpackedRGBA *dst = (UnpackedRGBA *)tPtr;
for (; src < srcEnd; src++, dst++)
{
// This call is the bottleneck now:
dst->Load(*src);
}
for (int i = 0; i < unpackedRawCount; i += vecSize)
{
Vector <uint> vi = new Vector <uint>(temp, i);
vi &= mask;
vi |= magicInt;
Vector <float> vf = Vector.AsVectorSingle(vi);
vf = (vf - magicFloat) * bVec;
vf.CopyTo(fTemp, i);
}
BufferPointer.Copy <uint>(tempBuf, (BufferPointer <byte>)destVectors, unpackedRawCount);
}
}
/// <inheritdoc />
internal override void ToXyzwBytes(BufferPointer <Color> sourceColors, BufferPointer <byte> destBytes, int count)
{
BufferPointer.Copy(sourceColors, destBytes, count);
}
/// <inheritdoc />
internal override void PackFromXyzwBytes(BufferPointer <byte> sourceBytes, BufferPointer <Color> destColors, int count)
{
BufferPointer.Copy(sourceBytes, destColors, count);
}
