UUIDs in schematic files v6

Schematic
1

I’m a bit confused about the kind of UUIDs supposed to be used in KiCad v6 schematics files, but more generally in the S-Expression format.

According to the spec,

The UUID attribute is a SHA256 hash that is unique for every object in a KiCad file format.

But looking at a few schematic files, UUIDs generated by KiCad seem to be type 4 - for instance: “8efee08b-b92e-4ba6-8722-c058e18114fe” - which are not SHA-based, but fully random.

Could you tell us more about that, and if that actually matters? (Reason I ask is I’m thinking of writing a tool to generate KiCad schematics.)

2

If you just want to generate the schematic, you can omit those and KiCad will generate them for you when you open the file. Probably this is a hack, but worked for me. See Programmatically generating schematic

3

Ah, thanks!

But I’d still like to get an answer to my question, because the documentation is confusing, and doesn’t seem to match reality.

4

Well, which one is right then, documentation or reality?

I already linked to the authoritative answer, i.e. source code, in the mentioned thread: common/kiid.cpp · master · KiCad / KiCad Source Code / kicad · GitLab

5

We use the pseudo-random number generator mt19937 (as defined in “Mersenne Twister: A 623-dimensionally equidistributed uniform pseudo-random number generator”, Makoto Matsumoto and Takuji Nishimura, ACM Transactions on Modeling and Computer Simulation: Special Issue on Uniform Random Number Generation, Vol. 8, No. 1, January 1998, pp. 3-30) to generate our UUIDs.

They should be globally unique, not just unique within a document. But we don’t currently rely on that.

2 Likes
6

Thanks. So is the part of the documentation I mentioned erroneous? (I suppose so…)

7

Thanks. So is the part of the documentation I mentioned erroneous? (I suppose so…)

Only if you look quickly. :wink:

1 Like
8

So what did I miss? :slight_smile:

9

Jeff did a sneaky update to correct the dev docs :slight_smile:

1 Like
10

Oh, just saw that. Well, as long as I could help… =) And thanks for the fix.

11

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