workbench/libs/mathieeedoubbas/ieeedpflt.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubbas_intern.h"
   7
   8 /*
   9     FUNCTION
  10
  11
  12     RESULT
  13       IEEE double precision number
  14
  15         Flags:
  16           zero     : result is zero
  17           negative : result is negative
  18           overflow : 0
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29
  30     HISTORY
  31 */
  32
  33 AROS_LHQUAD1(double, IEEEDPFlt,
  34     AROS_LHAQUAD(LONG, y, D0, D1),
  35     struct MathIeeeDoubBasBase *, MathIeeeDoubBasBase, 6, MathIeeeDoubBas
  36 )
  37 {
  38     AROS_LIBFUNC_INIT
  39
  40     LONG Exponent = 0;
  41     LONG TestMask = 0xFFFFFFFF;
  42     QUAD Res, yQuad, ExponentQuad;
  43     double * DRes = (double *)&Res;
  44
  45     Set_Value64C(Res,0,0);
  46
  47     if (0 == y)
  48     {
  49         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  50         return *DRes; /* return 0 */
  51     }
  52
  53     if (y < 0 )
  54     {
  55         Set_Value64C(Res, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  56         y = -y;
  57     }
  58     /* find out which is the number of the highest set bit */
  59     while (TestMask & y)
  60     {
  61         Exponent ++;
  62         TestMask <<= 1;
  63     }
  64
  65     SHL32(yQuad , y , (53 - Exponent) );
  66
  67     AND64QC(yQuad,  IEEEDPMantisse_Mask_Hi, IEEEDPMantisse_Mask_Lo);
  68
  69     Exponent += 0x3fe;
  70
  71     /* adapt Exponent to IEEEDP-Format */
  72     SHL32(ExponentQuad, Exponent, 52);
  73     OR64Q(Res, yQuad);
  74     OR64Q(Res, ExponentQuad);
  75     if ( is_lessSC(Res,0,0) ) /* Res < 0 */
  76     {
  77         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  78     }
  79
  80     return *DRes;
  81
  82     AROS_LIBFUNC_EXIT
  83 }