workbench/libs/mathtrans/spfieee.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathtrans_intern.h"
   7
   8 /*****************************************************************************
   9
  10     NAME */
  11
  12         AROS_LH1(float, SPFieee,
  13
  14 /*  SYNOPSIS */
  15         AROS_LHA(float, ieeenum, D0),
  16
  17 /*  LOCATION */
  18         struct Library *, MathTransBase, 18, MathTrans)
  19
  20 /*  FUNCTION
  21         Convert single precision ieee number to FFP number
  22
  23     INPUTS
  24
  25     RESULT
  26         Motorola fast floating point number
  27
  28         flags:
  29          zero     : result is zero
  30          negative : result is negative
  31          overflow : exponent of the ieee-number was out of range for
  32                     ffp
  33
  34     BUGS
  35
  36     INTERNALS
  37
  38 *****************************************************************************/
  39 {
  40     AROS_LIBFUNC_INIT
  41
  42     LONG Res;
  43
  44     /* check for ieeenum == 0 */
  45     if (0 == ieeenum)
  46     {
  47         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  48         return 0;
  49     }
  50
  51     /* calculate the exponent  */
  52     Res = (ieeenum & IEEESPExponent_Mask) >> 23;
  53     Res = Res - 126 + 0x40;
  54
  55     /* exponent too big / small */
  56     if ((char) Res < 0)
  57     {
  58         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  59         return Res;
  60     }
  61
  62     Res |= (ieeenum << 8) | 0x80000000;
  63
  64     /* check ieeenum-number for a sign */
  65     if (ieeenum < 0)
  66     {
  67         Res |= FFPSign_Mask;
  68         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  69     }
  70
  71     return Res;
  72
  73     AROS_LIBFUNC_EXIT
  74 }