workbench/libs/mathtrans/sptan.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 tangens of a given FFP number in radians
  11
  12     RESULT
  13       Motorola fast floating point number
  14
  15       flags:
  16         zero     : result is zero
  17         negative : result is negative
  18         overflow :
  19
  20     NOTES
  21
  22     EXAMPLE
  23
  24     BUGS
  25
  26     SEE ALSO
  27
  28     INTERNALS
  29
  30     HISTORY
  31 */
  32
  33 AROS_LH1(float, SPTan,
  34     AROS_LHA(float, fnum1, D0),
  35     struct Library *, MathTransBase, 8, MathTrans
  36 )
  37 {
  38     AROS_LIBFUNC_INIT
  39
  40     LONG z,SIN,Res,ysquared,yabs,tmp;
  41     yabs = fnum1 & (FFPMantisse_Mask + FFPExponent_Mask);
  42
  43     if ((LONG)FFP_Pinfty == yabs)
  44     {
  45         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  46         return FFP_NAN;
  47     }
  48
  49     z = SPFloor(SPDiv(pi, yabs));
  50     tmp  = SPMul(z,pi);
  51     tmp |= FFPSign_Mask; /* tmp = -tmp; */
  52     yabs = SPAdd(yabs, tmp);
  53
  54     if ( (char)yabs > (char)pio2  &&  (yabs & FFPMantisse_Mask) > (pio2 & FFPMantisse_Mask) )
  55     {
  56         yabs |= FFPSign_Mask;
  57         yabs  =SPAdd(pi, yabs);
  58         tmp = TRUE;
  59     }
  60     else
  61     {
  62         tmp = FALSE;
  63     }
  64
  65     ysquared = SPMul(yabs,yabs);
  66                SIN = SPMul(yabs,
  67                SPAdd(sinf1,
  68                SPMul(ysquared,
  69                SPAdd(sinf2,
  70                SPMul(ysquared,
  71                SPAdd(sinf3,
  72                SPMul(ysquared,
  73                SPAdd(sinf4,
  74                SPMul(ysquared,
  75                SPAdd(sinf5,
  76                SPMul(ysquared, sinf6)))))))))));
  77     /* cos  */
  78     z   = SPAdd(cosf1,
  79           SPMul(ysquared,
  80           SPAdd(cosf2,
  81           SPMul(ysquared,
  82           SPAdd(cosf3,
  83           SPMul(ysquared,
  84           SPAdd(cosf4,
  85           SPMul(ysquared,
  86           SPAdd(cosf5,
  87           SPMul(ysquared, cosf6))))))))));
  88
  89     Res = SPDiv(z, SIN);
  90
  91     if ((char)fnum1 < 0 ) Res ^= FFPSign_Mask;
  92     if (TRUE == tmp)      Res ^= FFPSign_Mask;
  93
  94     if (0 == Res)
  95     {
  96         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  97         return 0;
  98     }
  99
 100     if ((char)Res < 0)
 101     {
 102         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 103     }
 104
 105     return Res;
 106
 107     AROS_LIBFUNC_EXIT
 108 }