Current Xoshiro128ss implementation is based on an incorrect version 1.0

[rinart73]

Current library implementation: https://github.com/michaeldzjap/rand-seed/blob/develop/src/Algorithms/Xoshiro128ss.ts#L40
Current version 1.1 written in C: https://xoshiro.di.unimi.it/xoshiro128starstar.c

There are 2 major differences:

1. Version 1.0 generated new number based on s[0] (this.a), rather than s[1] (this.b). This is explicitly marked as a mistake that they fixed:

Note that version 1.0 had mistakenly s[0] instead of s[1] as state word passed to the scrambler.

2. Rotl operation performed on generated number r has incorrect order of operations:

// current
r = (r << 7) | ((r >>> 25) * 9);
// proper
r = ((r << 7) | (r >>> 25)) * 9;

With changes applied new implementation will of course generate different numbers for the same seeds, which means it's not backwards compatible.

[michaeldzjap]

Thanks for reporting @rinart73 . Will pick this up as soon as I have time.