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     FUNCTION
  10       Convert single precision ieee number to FFP number
  11
  12     RESULT
  13       Motorola fast floating point number
  14
  15       flags:
  16          zero     : result is zero
  17          negative : result is negative
  18          overflow : exponent of the ieee-number was out of range for
  19                     ffp
  20
  21     NOTES
  22
  23     EXAMPLE
  24
  25     BUGS
  26
  27     SEE ALSO
  28
  29     INTERNALS
  30
  31     HISTORY
  32 */
  33
  34 AROS_LH1(float, SPFieee,
  35     AROS_LHA(float, ieeenum, D0),
  36     struct Library *, MathTransBase, 18, MathTrans
  37 )
  38 {
  39     AROS_LIBFUNC_INIT
  40
  41     LONG Res;
  42
  43     /* check for ieeenum == 0 */
  44     if (0 == ieeenum)
  45     {
  46         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  47         return 0;
  48     }
  49
  50     /* calculate the exponent  */
  51     Res = (ieeenum & IEEESPExponent_Mask) >> 23;
  52     Res = Res - 126 + 0x40;
  53
  54     /* exponent too big / small */
  55     if ((char) Res < 0)
  56     {
  57         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  58         return Res;
  59     }
  60
  61     Res |= (ieeenum << 8) | 0x80000000;
  62
  63     /* check ieeenum-number for a sign */
  64     if (ieeenum < 0)
  65     {
  66         Res |= FFPSign_Mask;
  67         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  68     }
  69
  70     return Res;
  71
  72     AROS_LIBFUNC_EXIT
  73 }