rom/mathffp/spdiv.c

   1 /*
   2     Copyright © 1995-2004, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathffp_intern.h"
   7
   8 /*
   9     FUNCTION
  10         Divide two ffp numbers
  11         fnum = fnum2 / fnum1;
  12
  13     RESULT
  14         Flags:
  15           zero     : result is zero
  16           negative : result is negative
  17           overflow : result is out of range
  18
  19     NOTES
  20
  21     EXAMPLE
  22
  23     BUGS
  24         The parameters are swapped !
  25
  26     SEE ALSO
  27
  28
  29     INTERNALS
  30       ALGORITHM:
  31         Check if fnum2 == 0: result = 0;
  32         Check if fnum1 == 0: result = overflow;
  33         The further algorithm comes down to a pen &amp; paper division
  34
  35     HISTORY
  36 */
  37
  38 AROS_LH2(float, SPDiv,
  39     AROS_LHA(float, fnum1, D1),
  40     AROS_LHA(float, fnum2, D0),
  41     struct LibHeader *, MathBase, 14, Mathffp
  42 )
  43 {
  44     AROS_LIBFUNC_INIT
  45
  46     LONG Res = 0;
  47     char Exponent = ((char) fnum2 & FFPExponent_Mask) -
  48                   ((char) fnum1 & FFPExponent_Mask) + 0x41;
  49
  50     LONG Mant2 = ((ULONG)fnum2 & FFPMantisse_Mask);
  51     LONG Mant1 = ((ULONG)fnum1 & FFPMantisse_Mask);
  52     ULONG Bit_Mask = 0x80000000;
  53
  54     /* check if the dividend is zero */
  55     if (0 == fnum2)
  56     {
  57         SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  58         return 0;
  59     }
  60
  61     /* check for division by zero */
  62     if (0 == fnum1)
  63     {
  64         SetSR(Overflow_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  65         return 0;
  66     }
  67
  68     while (Bit_Mask >= 0x40 && Mant2 != 0)
  69     {
  70         if (Mant2 - Mant1 >= 0)
  71         {
  72             Mant2 -= Mant1;
  73             Res |= Bit_Mask;
  74
  75             while (Mant2 > 0)
  76             {
  77                 Mant2 <<= 1;
  78                 Bit_Mask >>= 1;
  79             }
  80
  81             while (Mant1 > 0)
  82             {
  83                 Mant1 <<=1;
  84                 Bit_Mask <<=1;
  85             }
  86         } /* if */
  87         else
  88         {
  89             Mant1 = (ULONG) Mant1 >> 1;
  90             Bit_Mask >>= 1;
  91         }
  92     } /* while */
  93
  94     /* normalize the mantisse */
  95     while (Res > 0)
  96     {
  97         Res += Res;
  98         Exponent --;
  99     }
 100
 101     if ((char) Res < 0)
 102     {
 103         Res += 0x00000100;
 104     }
 105
 106     Res &= FFPMantisse_Mask;
 107     Res |= (Exponent & 0x7f);
 108     Res |= (fnum1 & FFPSign_Mask) ^ (fnum2 & FFPSign_Mask);
 109
 110     if ((char) Res < 0)
 111     {
 112         SetSR(Negative_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
 113     }
 114
 115     if ((char) Exponent < 0)
 116     {
 117         SetSR(Overflow_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
 118         return(Res | (FFPMantisse_Mask | FFPExponent_Mask));
 119     }
 120
 121     kprintf("%x / %x =%x\n",fnum2,fnum1,Res);
 122
 123     return Res;
 124
 125     AROS_LIBFUNC_EXIT
 126 }