Kushal Das

FOSS and life. Kushal Das talks here.


Story of a space

In my case the story continued for around 2 hours. Yesterday I was trying to implement something from a given SPEC, and tried to match my output (from Rust) with the output from the Python code written by Dr. Fett.

The problem

I had to get the JSON encoding from an ordered Array (in Python it is a simple list), say ["kushal", "das"], and get the base64urlencode(sha256sum(JSON_ENCODED_STRING)) in Rust using serde_json.

Easy, isn’t?

Let us see what the encoded string looks like:


And the final checksum is otcxXDbO4_xzK0DXL_DO2INIFXIJdO1PqVM-n_gt-3g.

But, the reference implementation in Python has the checksum as fUMdn88aaoyKTHrvZd6AuLmPraGhPJ0zF5r_JhxCVZs.

It took me a few hours to notice the space after comma in the JSON encoded string from Python:

"[\"6Ij7tM-a5iVPGboS5tmvVA\", \"John\"]"

This is due to the following line from JSON spec

Insignificant whitespace is allowed before or after any of the six structural characters.

Yes, I know I should have known better, and read the original spec properly. But, in this case I learned it in the hard way.