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