workbench/libs/mathieeedoubbas/ieeedpflt.c

   1 /*
   2     Copyright © 1995-2017, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubbas_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LH1(double, IEEEDPFlt,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(LONG, y, D0),
  16
  17 /*  LOCATION */
  18         struct MathIeeeDoubBasBase *, MathIeeeDoubBasBase, 6, MathIeeeDoubBas)
  19
  20 /*  FUNCTION
  21         Convert an integer into an IEEE double precision floating point
  22         number.
  23
  24     INPUTS
  25         y - a 32-bit integer.
  26
  27     RESULT
  28         x - IEEE double precision floating point number.
  29
  30         Flags:
  31           zero     : result is zero
  32           negative : result is negative
  33           overflow : 0
  34
  35     NOTES
  36
  37     EXAMPLE
  38
  39     BUGS
  40
  41     SEE ALSO
  42         IEEEDPFix()
  43
  44     INTERNALS
  45
  46 *****************************************************************************/
  47 {
  48     AROS_LIBFUNC_INIT
  49
  50     LONG Exponent = 0;
  51     LONG TestMask = 0xFFFFFFFF;
  52     QUAD Res, yQuad, ExponentQuad;
  53     double * DRes = (double *)&Res;
  54
  55     Set_Value64C(Res,0,0);
  56
  57     if (0 == y)
  58     {
  59         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  60         return *DRes; /* return 0 */
  61     }
  62
  63     if (y < 0 )
  64     {
  65         Set_Value64C(Res, IEEEDPSign_Mask_Hi, IEEEDPSign_Mask_Lo);
  66         y = -y;
  67     }
  68     /* find out which is the number of the highest set bit */
  69     while (TestMask & y)
  70     {
  71         Exponent ++;
  72         TestMask <<= 1;
  73     }
  74
  75     SHL32(yQuad , y , (53 - Exponent) );
  76
  77     AND64QC(yQuad,  IEEEDPMantisse_Mask_Hi, IEEEDPMantisse_Mask_Lo);
  78
  79     Exponent += 0x3fe;
  80
  81     /* adapt Exponent to IEEEDP-Format */
  82     SHL32(ExponentQuad, Exponent, 52);
  83     OR64Q(Res, yQuad);
  84     OR64Q(Res, ExponentQuad);
  85     if ( is_lessSC(Res,0,0) ) /* Res < 0 */
  86     {
  87         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  88     }
  89
  90     return *DRes;
  91
  92     AROS_LIBFUNC_EXIT
  93 }