Re: [bug-mes] Simple division algorithm

[Jan Nieuwenhuizen]

Danny Milosavljevic writes:

> ARM doesn't have an integer division instruction.
>
> I suggest a function like this:

That looks fine.

> diff --git a/lib/mes/ntoab.c b/lib/mes/ntoab.c
> index 640fcc6a..55eee1be 100644
> --- a/lib/mes/ntoab.c
> +++ b/lib/mes/ntoab.c
> @@ -20,6 +20,30 @@
>  
>  #include <mes/lib.h>
>  
> +static int __idiv(long a, long b, int* remainder)
> +{
> +       *remainder = 0;
> +       if (b == 1)
> +               return a;
> +       else if (b == 0)
> +               return 42; /* FIXME how to abort */

What about (copied partly frcom mes/fdungetc, but adding abort (we
should do that in fdungetc too).

      eputs (" ***MES C LIB*** divide by zero numerator=");
      eputs (itoa (a));
      eputs ("\n");
      assert (0);

> +       else
> +       {
> +               long x;
> +               int negative_result = (a < 0) ^ (b < 0);
> +               if (a < 0)
> +                       a = -a;
> +               if (b < 0)
> +                       b = -b;
> +               for (x = 0; a >= b; a -= b)
> +                       ++x;
> +               *remainder = a;
> +               if (negative_result)
> +                       x = -x;
> +               return x;
> +       }
> +}
> +
>
> Functions whose names start with "__" are reserved in C and can thus be used 
> for "builtins".
>
> Where should we put the builtins?

What about lib/mes/__idiv.c and #include it in lib/libc.c (assuming
that is where we need it).

> Is the name OK?

Yes, I think so.
thanks!
janneke

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Jan Nieuwenhuizen <address@hidden> | GNU LilyPond http://lilypond.org
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