Re: [boost] [uuid] uuid::create() function

From: Jos Hickson (jos.hickson_at_[hidden])
Date: 2007-06-05 10:41:44

On 05/06/07, Peter Dimov <pdimov_at_[hidden]> wrote:
> Jos Hickson wrote:
>
> > Understood.  However, if the best implementation of uuid::create()
> > depends on which of two usage patterns is assumed ("batch" or "one per
> > program") maybe a better approach is to have both uuid_generator (for
> > batch purposes) and uuid::create() (for the one-per-program usage)
> > with the generator seeded using the randomness that uuid::create()
> > uses.
>
> We can consider dropping the two forms of uuid::create entirely and only
> provide uuid_generator. The discussion has demonstrated that they have some
> non-obvious pitfalls (one is slower than expected, the other assumes that
> the user has supplied a good seed and this is unlikely).
>
> class uuid_generator
> {
>     unsigned rd_[5];
>     mt19937 en_;
>
>     uuid_generator()
>     {
>         init rd_;
>         seed en_ with rd_[4];
>     }
>
>     operator()
>     {
>         generate a 128-bit number using en_;
>         xor it with rd_[0..3];
>         return a uuid based on it;
>     }
> };
>
> seems to address both issues.
>

Yes, that's probably a better idea but if both versions of create()
are dropped then should there be some means of providing a different
engine for those who really want to?

Jos