rom/mathieeesingbas/ieeespfloor.c

   1 /*
   2     Copyright © 1995-2004, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include "mathieeesingbas_intern.h"
   7
   8 /*
   9     FUNCTION
  10         Calculate the largest integer ieeesp-number less than or equal to
  11         fnum
  12
  13     RESULT
  14         IEEE single precision floating point
  15
  16         Flags:
  17           zero     : result is zero
  18           negative : result is negative
  19           overflow : 0 (???)
  20
  21     NOTES
  22
  23     EXAMPLE
  24        floor(10.5) = 10
  25        floor(0.5)  = 0
  26        floor(-0.5) = -1
  27        floor(-10.5)= -11
  28
  29     BUGS
  30
  31     SEE ALSO
  32         @Math.Floor@
  33
  34     INTERNALS
  35
  36     HISTORY
  37 */
  38
  39 AROS_LH1(float, IEEESPFloor,
  40     AROS_LHA(float, y, D0),
  41     struct LibHeader *, MathIeeeSingBasBase, 15, Mathieeesingbas
  42 )
  43 {
  44     AROS_LIBFUNC_INIT
  45
  46     LONG Mask = 0x80000000;
  47
  48     if (0x7f880000 == y) return y;
  49
  50     if ((y & IEEESPExponent_Mask)  < 0x3f800000)
  51     {
  52         if (y < 0) /* negative sign? */
  53         {
  54             SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  55             return 0xbf800000; /* -1 */
  56         }
  57         else
  58         {
  59             SetSR(Zero_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  60             return 0;
  61         }
  62     }
  63
  64     /* |fnum| >= 1 */
  65     Mask >>= ((y & IEEESPExponent_Mask) >> 23) - 0x77;
  66
  67     /* y is negative */
  68     if (y < 0)
  69     {
  70         /* is there anything behind the decimal dot? */
  71         if (0 != (y & (~Mask)) )
  72         {
  73             y    = IEEESPAdd(y, 0xbf800000 ); /* fnum = fnum -1; */
  74             Mask = 0x80000000;
  75             Mask >>= ((y & IEEESPExponent_Mask) >> 23) - 0x77;
  76         }
  77     }
  78
  79     if(y < 0) SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  80
  81     return y & Mask;
  82
  83     AROS_LIBFUNC_EXIT
  84 }