Listing 8

/* _Dunscale function - IEEE 754 version */
#include "xmath.h"

short _Dunscale(short *pex, double *px)
       {       /* separate *px to 1/2 <= |frac| < 1 and 2^*pex */
       unsigned short *ps = (unsigned short *)px;
       short xchar = (ps[_D0] & _DMASK) >> _D0FF;

       if (xchar == _DMAX)
              {       /* NaN or INF */
              *pex = 0;
              return (ps[_D0] & _DFRAC || ps[_D1]
                     || ps[_D2] || ps[_D3] ? NAN : INF);
              }
       else if (0 < xchar || (xchar = _Dnorm(ps)) != 0)
              {       /* finite, reduce to [1/2, 1) */
              ps[_D0] = ps[_D0] & _DMASK | _DBIAS << _D0FF;
              *pex = xchar - _DBIAS;
              return (FINITE);
              }
       else
              {       /* zero */
              *pex = 0;
              return (0);
              }
       }

/* End of File */