Hacker News Reader

Comment by computomatic | Hacker News Reader

16 random bytes is not a valid UUIDv4. I don’t think it needs to be in the standard library, but implementing the spec yourself is also not the right choice for 99% of cases.

View on HN

Well that depends on your luck, it could be a valid one about 1/16th of the time.

1/64, actually, because RFC-compliant (variant 1) UUIDv4 requires fixed values for both the version nibble and two bits of the variant nibble.

The fact that we're discussing this at all is a reasonable argument for using a library function.

While it might be invalid, will most libraries choke if you give them a pseudo UUIDv4?

What do you mean? Are you talking about validation of UUIDs?

If you generate random bytes, which are unlikely to conform to the UUIDv4 spec, my guess is that most libraries will silently accept the id. That is, generating random bytes, will probably work just work.

But what libraries are you talking about? What is their purpose?

Nice, thanks and I agree.

I didn't say about 16 random bytes. But you're almost there. You generate 16 random bytes and perform few bitwise operations to set version and variant bits correctly.

Not that it matters. I don't even think that there's a single piece of software in the world which would actually care about these bits rather than treating the whole byte array as opaque thing.

Let's call it a valid UUIDv0 - all bits randomized including the version bits :)

What if I generate 16 random bytes and use that as id?

No problem, just don't call it UUID

Reply on news.ycombinator.com