Encoding: The simple ZigZag formula is wrong about protocolbuffers.github.io HOT 3 CLOSED

@Logofile Do you have context on why this was changed?

The old version (~ 1 year ago) was correct:
(n << 1) ^ (n >> 31) for sint32
(n << 1) ^ (n >> 63) for sint64

This more closely matched our code as well

from protocolbuffers.github.io.

I think what we want is (n + n) ^ (n < 0), which is easy to prove is equivalent to the above formula (but more compact)

from protocolbuffers.github.io.

Nvm, your version is correct. Because of the right-shift behavior of signed integers we need the - like you found: (n+n) ^ -(n < 0). I think it's best to just use the version we have in the code though to make it more maintainable though

from protocolbuffers.github.io.