rom/utility/udivmod32.c

   1 /*
   2     Copyright © 1995-2001, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     Desc: UDivMod32 - divide two 32 bit numbers.
   6     Lang: english
   7 */
   8 #include "intern.h"
   9
  10 /*****************************************************************************
  11
  12     NAME */
  13 #include <proto/utility.h>
  14
  15         AROS_LH2(ULONG, UDivMod32,
  16
  17 /*  SYNOPSIS */
  18         AROS_LHA(ULONG, dividend, D0),
  19         AROS_LHA(ULONG, divisor, D1),
  20
  21 /*  LOCATION */
  22         struct Library *, UtilityBase, 26, Utility)
  23
  24 /*  FUNCTION
  25         Perform the 32 bit unsigned division and modulus of dividend by
  26         divisor, that is dividend / divisor. Will return both the
  27         quotient and the remainder.
  28
  29     INPUTS
  30         dividend        -   The number to divide into (numerator).
  31         divisor         -   The number to divide by (denominator).
  32
  33     RESULT
  34         For m68k assembly programmers,
  35             D0: quotient
  36             D1: remainder
  37
  38         For HLL programmers,
  39             the quotient
  40
  41     NOTES
  42         The utility.library math functions are unlike all other utility
  43         functions in that they don't require the library base to be
  44         loaded in register A6, and they also save the values of the
  45         address registers A0/A1.
  46
  47         This function is mainly to support assembly programers, and is
  48         probably of limited use to higher-level language programmers.
  49
  50     EXAMPLE
  51
  52     BUGS
  53         It is impossible for C programmers to obtain the value of
  54         remainder.
  55
  56     SEE ALSO
  57         SDivMod32(), SMult32(), SMult64(), UMult32(), UMult64()
  58
  59     INTERNALS
  60         May actually be handled by code that is in config/$(KERNEL)
  61         This is the case for m68k-native.
  62
  63     HISTORY
  64         29-10-95    digulla automatically created from
  65                             utility_lib.fd and clib/utility_protos.h
  66
  67 *****************************************************************************/
  68 {
  69     AROS_LIBFUNC_INIT
  70
  71     return dividend / divisor;
  72
  73 #if 0
  74 #error The UDivMod32() emulation code does NOT work!
  75
  76     /* This does _NOT_ work, so do not use it */
  77
  78     UWORD a,b,c,d;
  79     UQUAD result;
  80     LONG quo, rem;
  81
  82     a = dividend >> 16;
  83     b = dividend & 0xFFFF;
  84     c = divisor >> 16;
  85     d = divisor & 0xFFFF;
  86
  87     /* See if the numerator is 32 bits or 16... */
  88     if(a == 0)
  89     {
  90         /* 16 bits */
  91         if(c != 0)
  92         {
  93             /* 16/32 -> quo = 0; rem = dividend */
  94             quo = 0;
  95             rem = dividend;
  96         }
  97         else
  98         {
  99             /* 16/16 -> can be done in native div */
 100             quo = b / d;
 101             rem = b % d;
 102         }
 103     }
 104     else
 105     {
 106         /* 32 bit numerator */
 107         if(c != 0)
 108         {
 109             /* 32 bit denominator, quo ~= a/c */
 110             quo = a/c;
 111         }
 112         else
 113         {
 114             /* 16 bit denominator, quo ~= (a/d) * 65536 */
 115             quo = (a / d) << 16;
 116         }
 117         /* Get the error */
 118         rem = dividend - UMult32(quo,divisor);
 119
 120         /* Take the remainder down to zero */
 121         while(rem > 0)
 122         {
 123             quo++;
 124             rem -= divisor;
 125         }
 126
 127         /* However a -ve remainder is silly,
 128            this also catches the case when the remainder is < 0 from the
 129            guess
 130         */
 131         while(rem < 0)
 132         {
 133             quo--;
 134             rem += divisor;
 135         }
 136     }
 137     SET_HIGH32OF64(result, quo);
 138     SET_LOW32OF64(result, rem);
 139
 140     return result;
 141
 142 #endif
 143     AROS_LIBFUNC_EXIT
 144
 145 } /* UDivMod32 */