Re: Integrated hashtables, take 3

[Fergus Henderson <fjh at cs dot mu dot oz dot au>]

On 19-May-2001, Neil Booth <neil@daikokuya.demon.co.uk> wrote:
> --- c-lang.c	2001/03/20 02:57:27	1.49
> +++ c-lang.c	2001/05/19 22:04:53
> @@ -59,7 +59,10 @@ c_post_options ()
>  static void
>  c_init_options ()
>  {
> -  parse_in = cpp_create_reader (CLK_GNUC89);
> +  /* Make identifier nodes long enough for the language-specific slots.  */
> +  set_identifier_size (sizeof (struct lang_identifier));
> +
> +  parse_in = cpp_create_reader (ident_hash, CLK_GNUC89);

I think that should be done in c_init() rather than in c_init_options().

> --- objc-act.c	2001/05/16 06:22:15	1.82
> +++ objc-act.c	2001/05/19 22:07:51
> @@ -727,7 +727,10 @@ generate_struct_by_value_array ()
>  static void
>  objc_init_options ()
>  {
> -  parse_in = cpp_create_reader (CLK_OBJC);
> +  /* Make identifier nodes long enough for the language-specific slots.  */
> +  set_identifier_size (sizeof (struct lang_identifier));
> +
> +  parse_in = cpp_create_reader (ident_hash, CLK_OBJC);
>    c_language = clk_objective_c;
>  }

Likewise.

> Index: hashtable.c
...
> +static unsigned int
> +calc_hash (str, len)
> +     const unsigned char *str;
> +     unsigned int len;
> +{
> +  unsigned int n = len;
> +  unsigned int r = 0;
> +#define HASHSTEP(r, c) ((r) * 67 + (c - 113));
> +
> +  while (n--)
> +    r = HASHSTEP (r, *str++);
> +
> +  return r + len;
> +#undef HASHSTEP
> +}

As a matter of style, I would recomment putting the macro
arguments in parentheses:

	s/c - 113/(c) - 113/

> +/* Return the approximate positive square root of a number N.  This is for
> +   statistical reports, not code generation.  */
> +double
> +approx_sqrt (x)
> +     double x;
> +{
> +  double s, d;
> +
> +  if (x < 0)
> +    abort ();
> +  if (x == 0)
> +    return 0;
> +
> +  s = x;
> +  do
> +    {
> +      d = (s * s - x) / (2 * s);
> +      s -= d;
> +    }
> +  while (d > .0001);
> +  return s;
> +}

I know you only moved this code around...
but what's the rationale for not just using sqrt()?

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.