"Peter Dimov" <pdimov@mmltd.net> wrote in news:002e01c790c0$0f2d3510$6407a80a@pdimov2:
Andy wrote:
I agree that the create function needs improvement. It suffers from threading problems (because of static variables) and from a hard coded random number generator (also a hard coded seed).
My solution is to create a generator class, as follows:
// maybe a better name // maybe a different default random number generator template <typename UniformRandomNumberGenerator = boost::mt19937> class random_guid_generator : boost::noncopyable
[...]
random_guid_generator<> guid_gen; guid g = guid_gen.create();
Why not just add an Engine & e parameter to guid::create?
Good idea. Something like: template<typename Engine> boost::guid guid::create(Engine& e = boost::mt19937(get_seed())); where get_seed() does something like what you said below. I want to be able to call the create function with a default Engine because I don't want to force users to create one themselves. The only downside is for people who do want a different engine/seed, they will have to pass that engine to the function everytime they call it.
For the default seed, you might want to look into combining several sources of entropy (unpredictable values) such as
- time(0) - clock() - the values of an unsigned char[] array that is allocated on the stack and not initialized - the addresses of some variables or functions - the address of a newly allocated object - anything else that you can come up with
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Andy.