units.cpp

#include "units.hpp"

namespace Sass {

  double conversion_factors[6][6] = {
             /*  in         cm         pc         mm         pt         px     */
    /* in */ { 1,         2.54,      6,         25.4,      72,        96        },
    /* cm */ { 1.0/2.54,  1,         6.0/2.54,  10,        72.0/2.54, 96.0/2.54 },
    /* pc */ { 1.0/6.0,   2.54/6.0,  1,         25.4/6.0,  72.0/6.0,  96.0/6.0  },
    /* mm */ { 1.0/25.4,  1.0/10.0,  6.0/25.4,  1,         72.0/25.4, 96.0/25.4 },
    /* pt */ { 1.0/72.0,  2.54/72.0, 6.0/72.0,  25.4/72.0, 1,         96.0/72.0 },
    /* px */ { 1.0/96.0,  2.54/96.0, 6.0/96.0,  25.4/96.0, 72.0/96.0, 1         }
  };

  Unit string_to_unit(const string& s)
  {
    if      (s == "in") return IN;
    else if (s == "cm") return CM;
    else if (s == "pc") return PC;
    else if (s == "mm") return MM;
    else if (s == "pt") return PT;
    else if (s == "px") return PX;
    else                return INCOMMENSURABLE;
  }

  double conversion_factor(const string& s1, const string& s2)
  {
    Unit u1 = string_to_unit(s1);
    Unit u2 = string_to_unit(s2);
    double factor;
    if (u1 == INCOMMENSURABLE || u2 == INCOMMENSURABLE)
      factor = 0;
    else
      factor = conversion_factors[u1][u2];
    return factor;
  }

  double convert(double n, const string& from, const string& to)
  {
    double factor = conversion_factor(from, to);
    return factor ? factor * n : n;
  }

}