Cubic Interpolation - part 1

gistfile1.txt

    static const poly_float kCubicOne(0.0f, 1.0f, 0.0f, 0.0f);
    static const poly_float kCubicTwo(-1.0f, -1.0f, 1.0f, 1.0f);
    static const poly_float kCubicThree(-2.0f, -2.0f, -2.0f, -1.0f);
    static const poly_float kCubicMult(-1.0f / 6.0f, 1.0f / 2.0f, -1.0f / 2.0f, 1.0f / 6.0f);
    
    forcedinline poly_float getCubicInterpolationValues(poly_float t) {
      return kCubicMult * (t + kCubicOne) * (t + kCubicTwo) * (t + kCubicThree);
    }
    
    forcedinline poly_float interpolateBuffers(const mono_float* const* buffers,
                                               const poly_int indices) {
      poly_int start_index = utils::shiftRight(indices, kIntermediateBits);
      poly_float result;
      poly_float t = utils::toFloat(indices & kIntermediateMask) * (1.0f / kIntermediateMult);

      for (int i = 0; i < poly_float::size(); ++i) {
        poly_float mult = utils::getCubicInterpolationValues(t[i]);
        poly_float sample = mult * utils::toPolyFloatFromUnaligned(buffers[i] + start_index[i]);
        result[i] = sample.sum();
      }
      return result;
    }