workbench/libs/mathieeedoubtrans/ieeedptieee.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeedoubtrans_intern.h"
   7
   8 /*
   9     FUNCTION
  10         Convert IEEE double to IEEE single precision number
  11
  12     RESULT
  13         IEEE single precision number
  14
  15         Flags:
  16           zero     : result is zero
  17           negative : result is negative
  18           overflow : value was out of range for IEEE single precision
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29
  30     HISTORY
  31 */
  32
  33 AROS_LHQUAD1(LONG, IEEEDPTieee,
  34     AROS_LHAQUAD(double, y, D0, D1),
  35     struct MathIeeeDoubTransBase *, MathIeeeDoubTransBase, 17, MathIeeeDoubTrans
  36 )
  37 {
  38     AROS_LIBFUNC_INIT
  39
  40     LONG Res, tmp;
  41
  42     SetSR(0, Zero_Bit | Overflow_Bit | Negative_Bit );
  43
  44     if (is_eqC(y, 0x0, 0x0))
  45     {
  46         SetSR(Zero_Bit, Zero_Bit | Overflow_Bit | Negative_Bit );
  47         return 0;
  48     }
  49
  50     SHRU32(Res, y, 52 );
  51     SHRU32(tmp, y, 29 );
  52     /* calculate the exponent */
  53     Res &=0x7ff;
  54     Res = Res + 0x7e - 0x3fe;
  55     Res <<= 23;
  56
  57     Res |= (tmp & IEEESPMantisse_Mask);
  58
  59     if (is_lessSC(y, 0x0, 0x0))
  60     {
  61         SetSR(Negative_Bit, Zero_Bit | Overflow_Bit | Negative_Bit );
  62         Res |= IEEESPSign_Mask;
  63     }
  64
  65     return Res;
  66
  67     AROS_LIBFUNC_EXIT
  68 }