saturate_cast.hpp

#ifndef SATURATE_CAST_HPP
#define SATURATE_CAST_HPP

#include <cmath>

// because C++ doesn't allow partial function
// specialization, we must use static method
// from specialized class

//-----------
//  EXAMPLE :
//----------
//  int v_255 = saturate_cast<float, int>(256.f);
//  double pi_d = saturate_cast<double, double>(M_PI);

namespace saturate_cast_detail {

  // definition for uint<n>_t
  template <typename In, typename Out>
  struct F
  {
    static Out impl(const In& i)
    {
      return std::max( (In)(0) , std::min( (In)((256<<sizeof(In))-1),  i ));
    }
  };

  // specialization for float 
  template <typename In>
  struct F<In,float>
  {
    static float impl(const In& i)
    {
      return i;
    }
  };

  // specialization for double
  template <typename In>
  struct F<In,double>
  {
    static double impl(const In& i)
    {
      return i;
    }
  };
}

template< class In, class Out >
Out saturate_cast(In in) { return saturate_cast_detail::F<In, Out>::impl(in); }