_STD_BEGIN _CRTIMP2 short _Dscale(double *px, long lexp) { /* scale *px by 2^xexp with checking */ unsigned short *ps = (unsigned short *)px; short xchar = (ps[_D0] & _DMASK) >> _DOFF; if (xchar == _DMAX) return ((ps[_D0] & _DFRAC) != 0 || ps[_D1] != 0 || ps[_D2] != 0 || ps[_D3] != 0 ? NAN : INF); else if (xchar == 0 && 0 < (xchar = _Dnorm(ps))) return (0); lexp += xchar; if (_DMAX <= lexp) { /* overflow, return +/-INF */ *px = ps[_D0] & _DSIGN ? -_Inf._D : _Inf._D; return (INF); } else if (0 < lexp) { /* finite result, repack */ ps[_D0] = ps[_D0] & ~_DMASK | (short)lexp << _DOFF; return (FINITE); } else { /* denormalized, scale */ unsigned short sign = ps[_D0] & _DSIGN; ps[_D0] = 1 << _DOFF | ps[_D0] & _DFRAC; if (--lexp < -(48+_DOFF)) { /* underflow, return +/-0 */ ps[_D0] = sign, ps[_D1] = 0; ps[_D2] = 0, ps[_D3] = 0; return (0); } else { /* nonzero, align fraction */ short xexp; for (xexp = (short)lexp; xexp <= -16; xexp += 16) { /* scale by words */ ps[_D3] = ps[_D2], ps[_D2] = ps[_D1]; ps[_D1] = ps[_D0], ps[_D0] = 0; } if ((xexp = -xexp) != 0) { /* scale by bits */ ps[_D3] = ps[_D3] >> xexp | ps[_D2] << (16 - xexp); ps[_D2] = ps[_D2] >> xexp | ps[_D1] << (16 - xexp); ps[_D1] = ps[_D1] >> xexp | ps[_D0] << (16 - xexp); ps[_D0] >>= xexp; } ps[_D0] |= sign; return (FINITE); } }
short _Dunscale(short *pex, double *px) { /* separate *px to 1/2 <= |frac| < 1 and 2^*pex */ _Dval *ps = (_Dval *)(char *)px; short xchar = (ps->_Sh[_D0] & _DMASK) >> _DOFF; if (xchar == _DMAX) { /* NaN or INF */ *pex = 0; return ((ps->_Sh[_D0] & _DFRAC) != 0 || ps->_Sh[_D1] != 0 || ps->_Sh[_D2] != 0 || ps->_Sh[_D3] != 0 ? _NANCODE : _INFCODE); } else if (0 < xchar || (xchar = _Dnorm(ps)) <= 0) { /* finite, reduce to [1/2, 1) */ ps->_Sh[_D0] = (ps->_Sh[_D0] & ~_DMASK) | _DBIAS << _DOFF; *pex = xchar - _DBIAS; return (_FINITE); } else { /* zero */ *pex = 0; return (0); } }