Don't understand codec tests for SInt64 / UInt64.

[ETiV]

https://github.com/pomelonode/pomelo-protobuf/blob/master/test/codecTest.js

as the code for uInt64 codec test:

var limit = 0x7fffffffffffffff;

Why use a 0~1 random number to multiple 0x7FFF FFFF FFFF FFFF as a limitation? (63bits)
WHY NOT using 0xFFFF FFFF FFFF FFFF? (64bits)

AND otherwise ...

the code for sInt64 codec test:

    var limit = 0xfffffffffffff;

It's 54bits.

But for signed int 64bit, because it's been multiple 2 inside the encode function, the limit should be 0x3FFF FFFF FFFF FFFF. (62bits, the head bit for sign, second bit for *2).

So, is there any limitation on UInt64 / SInt64 codec?

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I've tested on my Objective-C codec. 0xFFFF...(64bits) works fine on UInt64, and 0x3FFF...(62bits) works find on SInt64.