On Friday, March 14, 2025, Jan Schultke wrote:

typedef std::array< char unsigned, (128u / CHAR_BIT) + !!(128u % CHAR_BIT)
>> > uuid_t;
>
>
> I think UUIDs would be a good fit for the C++ standard library, but as a
> vocabulary class type, not just some alias for an array.
>
> Keep in mind that there are different versions of UUIDs, and not every
> 128-bit pattern is a valid UUID. Version 4 in particular is the one
> populated with random numbers. If we did have 128-bit integers, this is how
> we could generate a random UUID:
>
> std::uint128_t random_uuid_v4() {
> return std::experimental::randint<std::uint128_t>(0, -1)
> & 0xffff'ffff'ffff'003f'ff0f'ffff'ffff'ffff // clear version
> and variant
> | 0x0000'0000'0000'0080'0040'0000'0000'0000; // set to version 4
> and IETF variant
> }
>
> Notice how certain bits are constant.
>



I'm not denying that that's how things started out.

But nowadays, whenever I need a UUID for anything, I just generate a
128-Bit random number. I don't manually set the 6 bits to indicate that
it's version 4. And I think that's what everyone else is doing now too.