workbench/libs/mathffp/spcmp.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         Compares two ffp numbers
  11
  12     RESULT
  13         <code>
  14        +1 : fnum1 > fnum2
  15         0 : fnum1 = fnum2
  16        -1 : fnum1 < fnum2
  17
  18
  19         Flags:
  20           zero     : fnum2 = fnum1
  21           negative : fnum2 < fnum1
  22           overflow : 0
  23         </code>
  24
  25     NOTES
  26
  27     EXAMPLE
  28
  29     BUGS
  30
  31     SEE ALSO
  32
  33
  34     INTERNALS
  35       ALGORITHM:
  36         <code>
  37         1st case:
  38           fnum1 is negative and fnum2 is positive
  39             or
  40           ( exponent(fnum1) < exponent(fnum2) and signs are equal )
  41           -> fnum1 < fnum2
  42
  43         2nd case:
  44           fnum1 is positive and fnum2 is negative
  45             or
  46           ( exponent(fnum1) > exponent(fnum2) and signs are equal )
  47           -> fnum2 > fnum1
  48
  49         now the signs and exponents must be equal
  50
  51         3rd case:
  52           fnum1 == fnum2
  53
  54         4th case:
  55           mantisse(fnum1) < mantisse(fnum2)
  56           -> fnum1 < fnum2
  57
  58         final case:
  59           fnum1 > fnum2
  60         </code>
  61     HISTORY
  62 */
  63
  64 AROS_LH2(LONG, SPCmp,
  65     AROS_LHA(float, fnum1, D1),
  66     AROS_LHA(float, fnum2, D0),
  67     struct LibHeader *, MathBase, 7, Mathffp
  68 )
  69 {
  70     AROS_LIBFUNC_INIT
  71
  72     D(kprintf("SPCmp(%08x,%08x)=", fnum1, fnum2));
  73
  74     /* fnum1 is negative and fnum2 is positive
  75     **  or
  76     ** exponent of fnum1 is less than the exponent of fnum2
  77     ** => fnum1 < fnum2
  78     */
  79     if ( (char)fnum1 < (char)fnum2 )
  80     {
  81         D(kprintf("-1\n"));
  82         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
  83         return -1;
  84     }
  85
  86     /* fnum1 is positive and fnum2 is negative
  87     **  or
  88     ** exponent of fnum1 is greater tban the exponent if fnum2
  89     ** => fnum1 > fnum2
  90     */
  91     if ((char) fnum1 > (char) fnum2 )
  92     {
  93         D(kprintf("1\n"));
  94         SetSR(0, Zero_Bit | Overflow_Bit | Negative_Bit );
  95         return 1;
  96     }
  97
  98     /*the signs and exponents of fnum1 and fnum2 must now be equal
  99     **fnum1 == fnum2
 100     */
 101     if (fnum1 == fnum2)
 102     {
 103         D(kprintf("0\n"));
 104         SetSR(Zero_Bit, Zero_Bit | Overflow_Bit | Negative_Bit);
 105         return 0;
 106     }
 107
 108     /* mantisse(fnum1) < mantisse(fnum2) */
 109     if (fnum1 < fnum2)
 110     {
 111         D(kprintf("-1\n"));
 112         SetSR(Negative_Bit, Zero_Bit | Negative_Bit | Overflow_Bit);
 113         return -1;
 114     }
 115
 116     /* Mantisse(fnum1) > mantisse(fnum2) */
 117     D(kprintf("1\n"));
 118     SetSR(0, Zero_Bit | Negative_Bit | Overflow_Bit);
 119     return 1;
 120
 121     AROS_LIBFUNC_EXIT
 122 }