dev: improve rlp.cairo to support recursive list

[Quentash]

Implemented recursive struct in rlp.cairo to be able to handle recursive list. I also tried to be as close as the code given in the ethereum doc ; https://ethereum.org/en/developers/docs/data-structures-and-encoding/rlp/ .

Here is a list of the biggest changes :

• Types have been reduced to only be String or List.
• decode_type() ( former from_bytes() ) now takes an array to be able to retrieve the long strings/lists size. It does now return the type which is either a string or a list, the offset at which it starts and its size.
• decode() is now recursively called in case of recursive lists.

Here is a screenshot of gas consommation before the modifications ;

And here is one after the modifications ;

It's worth noting that some tests show improvement.
For instance, the test_decode_string appears to consume more gas than before, but this test is essentially a loop that converts a single character into an array, explaining the increased gas consumption. But on the other hand, the test_decode_long_list test, which deals with a larger amount of bytes, consumes less gas than it did originally.

I am certain that there is still potential for further improvement, and I would appreciate feedback on the direction these changes are taking. Whether you agree or disagree with some of the modifications.

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

rlp.cairo.decode() doesn't handle recusrive list.

Resolves: #428

What is the new behavior?

• handle recursive list

Does this introduce a breaking change?

• Yes
• No

[Eikix]

First review, will have more questions in the coming days as I have more time to do a second review

[Quentash]

Made a better recursive implementation for the rlp_decode().
No more "Option::Error", no more loop!

[Quentash]

I had to downgrade starknet/cairo versions in scarb files back to 2.3.0-rc0 because the recursivity seems to fail in Cairo 2.3.0 giving a very strange error (see screenshot).

Which still appears on github CL/Tests.
To make the tests run on local, install scarb-rc1 or 0, they both seem to handle struct recursivity. I don't understand why the 2.3.0 break it yet, maybe an issue should be open on the compiler github ?

[Eikix]

Interestingly, there was a bug in the compiler, it'll be fixed in the next release

[Eikix]

lgtm

[Eikix]

Congratulations! Well fought