workbench/libs/mathtrans/spcosh.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       Calculate the hyperbolic cosine of the ffp number
  11
  12     RESULT
  13       Motorola fast floating point number
  14
  15       flags:
  16         zero     : result is zero
  17         negative : 0 (not possible)
  18         overflow : result too big for ffp-number
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29      <code>
  30       cosh(x) = (1/2)*( e^x + e^(-x) )
  31
  32       cosh( |x| >= 44 ) = infinity;
  33       cosh( |x| >= 9  ) = (1/2) * (e^x);
  34      </code>
  35
  36     HISTORY
  37 */
  38
  39 AROS_LH1(float, SPCosh,
  40     AROS_LHA(float, fnum1, D0),
  41     struct Library *, MathTransBase, 11, MathTrans
  42 )
  43 {
  44     AROS_LIBFUNC_INIT
  45
  46     ULONG Res;
  47     LONG tmp;
  48
  49     /* cosh(-x) = cosh(x) */
  50     fnum1 &= ( FFPMantisse_Mask + FFPExponent_Mask );
  51
  52     Res = SPExp(fnum1);
  53
  54     if ( FFP_Pinfty == Res )
  55     {
  56         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  57         return Res;
  58     }
  59
  60     tmp = (fnum1 & FFPExponent_Mask) - 0x41;
  61
  62     if ( tmp <= 2 || (tmp == 3 && (fnum1 & FFPMantisse_Mask) < 0x90000000) )
  63     {
  64         Res = SPAdd(Res, SPDiv(Res, one));
  65     }
  66
  67     /* Res = Res / 2 */
  68     /* should be ((char)Res) --, but gcc on Linux screws up the result  */
  69     tmp = Res & 0xFFFFFF00;
  70     Res -= sizeof(char);
  71     Res = tmp | Res;
  72
  73     if (0 == Res || (char)Res < 0 )
  74     {
  75         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  76         return 0;
  77     }
  78
  79     return Res;
  80
  81     AROS_LIBFUNC_EXIT
  82 }