From: Chiyuan Zhang <pluskid@...>
Date: 2008-03-02T01:16:33+09:00
Subject: Re: Ruby String hash key overflow when converting to Fixnum.

2008/3/1, Nobuyoshi Nakada <nobu@ruby-lang.org>:
> Hi,
>
>  At Sat, 1 Mar 2008 23:50:37 +0900,
>  Chiyuan Zhang wrote in [ruby-core:15713]:
>
> > Another more efficient way is to perform truncation when calculating
>  > String hash to make the result meet what we geet in Ruby world. Here's
>  > the patch:
>
>
> Then, shouldn't all results be in the Fixnum range?
>
Yeah, a more complete solution.
>
>  Index: hash.c
>  ===================================================================
>  --- hash.c      (revision 15666)
>  +++ hash.c      (working copy)
>  @@ -76,13 +76,14 @@ rb_any_hash(VALUE a)
>   {
>      VALUE hval;
>  +    int hnum;
>
>
>      switch (TYPE(a)) {
>        case T_FIXNUM:
>        case T_SYMBOL:
>  -       return (int)a;
>
> +       hnum = (int)a;
>
>         break;
>
>        case T_STRING:
>  -       return rb_str_hash(a);
>
> +       hnum = rb_str_hash(a);
>         break;
>
>  @@ -92,6 +93,8 @@ rb_any_hash(VALUE a)
>
>             hval = rb_funcall(hval, '%', 1, INT2FIX(536870923));
>         }
>
> -       return (int)FIX2LONG(hval);
>  +       hnum = (int)FIX2LONG(hval);
>      }
>  +    hnum <<= 1;
>  +    return RSHIFT(hnum, 1);
>   }
>
>
>
>
>  --
>  Nobu Nakada
>
>