From: George Moschovitis <george.moschovitis@...>
Date: 2006-11-26T03:06:27+09:00
Subject: Re: Problems with String#hash

The offending version is the 1.8.4 version that comes with Ubuntu
6.10, has anyone experienced similar problems?

-g.

On 11/24/06, Jan Svitok <jan.svitok@gmail.com> wrote:
> On 11/24/06, George Moschovitis <george.moschovitis@gmail.com> wrote:
> > Dear devs,
> >
> > I am facing a very NASTY problem with String#hash
> >
> > Here is the same code that I run on 3 different computers:
> >
> > root@kosh:~ # irb
> > irb(main):001:0> "User".hash
> > => 690465448
> > irb(main):002:0> VERSION
> > => "1.8.2"
> >
> > C:\Documents and Settings\drak>irb
> > irb(main):001:0> "User".hash
> > => 690465448
> > irb(main):002:0> VERSION
> > => "1.8.4"
> >
> > http://tryruby.hobix.com/
> >  Interactive ruby ready.
> > >> "User".hash
> > => 690465448
> > >> VERSION
> > => "1.8"
> >
> > root@victory:~# irb
> > irb(main):001:0> "User".hash
> > => -1457018200
> > irb(main):002:0> VERSION
> > => "1.8.4"
> >
> > Please nottice that on the last case I get a different result! Any
> > idea why this happens?
> >
> > thanks in advance for any help!
> >
> > George.
>
> string.c:851
> int
> rb_str_hash(str)
>     VALUE str;
> {
>     register long len = RSTRING(str)->len;
>     register char *p = RSTRING(str)->ptr;
>     register int key = 0;
>
> #if defined(HASH_ELFHASH)
>     register unsigned int g;
>
>     while (len--) {
>         key = (key << 4) + *p++;
>         if (g = key & 0xF0000000)
>             key ^= g >> 24;
>         key &= ~g;
>     }
> #elif defined(HASH_PERL)
>     while (len--) {
>         key += *p++;
>         key += (key << 10);
>         key ^= (key >> 6);
>     }
>     key += (key << 3);
>     key ^= (key >> 11);
>     key += (key << 15);
> #else
>     while (len--) {
>         key = key*65599 + *p;
>         p++;
>     }
>     key = key + (key>>5);
> #endif
>     return key;
> }
>
> I suspect those #ifdefs. See your config.h what's compiled in.
>
>


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