head	1.1;
access;
symbols
	version39-41:1.1;
locks;
comment	@ * @;


1.1
date	92.06.08.18.31.20;	author mwild;	state Exp;
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desc
@initial checkin
@


1.1
log
@Initial revision
@
text
@/*
 * ldexp returns the quanity "value" * 2 ^ "exp"
 *
 * For the mc68000 using IEEE format the double precision word format is:
 *
 * WORD N   =>    SEEEEEEEEEEEMMMM
 * WORD N+1 =>    MMMMMMMMMMMMMMMM
 * WORD N+2 =>    MMMMMMMMMMMMMMMM
 * WORD N+3 =>    MMMMMMMMMMMMMMMM
 *
 * Where:          S  =>   Sign bit
 *                 E  =>   Exponent
 *                 X  =>   Ignored (set to 0)
 *                 M  =>   Mantissa bit
 *
 * NOTE:  Beware of 0.0; on some machines which use excess 128 notation for the
 * exponent, if the mantissa is zero the exponent is also.
 *
 */

#define MANT_MASK 0x800FFFFF	/* Mantissa extraction mask     */
#define ZPOS_MASK 0x3FF00000	/* Positive # mask for exp = 0  */
#define ZNEG_MASK 0x3FF00000	/* Negative # mask for exp = 0  */

#define EXP_MASK 0x7FF00000	/* Mask for exponent            */
#define EXP_SHIFTS 20		/* Shifts to get into LSB's     */
#define EXP_BIAS 1023		/* Exponent bias                */


union dtol
{
  double dval;
  int ival[2];
};

double
ldexp (value, exp)
     double value;
     int exp;
{
  union dtol number;
  int *iptr, cexp;

  if (value == 0.0)
    return (0.0);
  else
    {
      number.dval = value;
      iptr = &number.ival[0];
      cexp = (((*iptr) & EXP_MASK) >> EXP_SHIFTS) - EXP_BIAS;
      *iptr &= ~EXP_MASK;
      exp += EXP_BIAS;
      *iptr |= ((exp + cexp) << EXP_SHIFTS) & EXP_MASK;
      return (number.dval);
    }
}
@