Two's complement Upscaler

2s_comp.cpp

template <typename Target, size_t Length>
// https://www.codeproject.com/Tips/1079637/Twos-Complement-for-Unusual-Integer-Sizes
class TwosComplementUpscaler
{
  Target bitfield : Length;
  
  TwosComplementUpscaler(Target value) : bitfield(value){}
  TwosComplementUpscaler();
  
public:
  static Target Convert(Target value)
  {
    static_assert(sizeof(Target) * 8 > Length, "Length too large");
    static_assert(Length > 1, "Length too short");
    
    Target mask = (~0) << Length;
    TwosComplementUpscaler temp(value & ~mask);
    return static_cast<Target>(temp.bitfield);
  }
};