How to de/encode bytes into an address array in Vyper? - ethereum

Question

I'm trying to implement Aave flash loan receiver in Vyper https://developers.aave.com/#implementing-a-flashloanreceiver-contract and I need to pass it an array of addresses as 'bytes memory _params' arg. Any ideas how do I encode an array of addresses to bytes in web3 and then decode them back from bytes to address[n] array in Vyper?

Answer 1

not sure what development environment you've opted with but Ethereum's Brownie has an Aave Flash-Loan template
if you already use brownie, to skip to the FLASH LOAN TEMPLATE section
otherwise, to install brownie there are a few requirements
check to see that you have node.js and npm already installed:
node -v
npm -v
if not run:
npm install -g npm
next install ganache-cli:
npm install -g ganache-cli
ganache-cli --version
if you don't have it already, install the latest python, then install pipx:
python -m pip install --user pipx
python -m pipx ensurepath
now install brownie:
pipx install eth-brownie
FLASH LOAN TEMPLATE:
check to make sure brownie is there, open a terminal and type:
brownie
to create a new project in brownie simply create a new directory to work in:
mkdir new_dir
cd new_dir
once in the new directory use the brownie key-word bake to create one of the templates available, see full list and instantiation instructions for each template at https://github.com/brownie-mix:
brownie bake aave-flashloan
and voila, you have a nice pre-made template and clear instructions for making it your own
if you want more info on brownie and testing with the brownie framework, i highly recommend reading Ben Hauser's many medium posts on the subject, he created the brownie framework and its pretty amazing, he can be found here https://iamdefinitelyahuman.medium.com/

Answer 2

addrBytes: Bytes[128] = concat(convert(32, bytes32), convert(2, bytes32), convert(addr0, bytes32), convert(addr1, bytes32))
funcsig: Bytes[4] = method_id("methodName(address[])")
full_data:Bytes[132] = concat(funcsig, addrBytes)
response: Bytes[128] = raw_call(contract_address, full_data, max_outsize=128)
result_address0: address = convert(slice(response, 64, 32), address)
result_address1: address = convert(slice(response, 96, 32), address)
This is the example if you want to pass a 2-length address array.
And I attach the reference to how you can encode dynamic arguments.
https://docs.soliditylang.org/en/v0.8.3/abi-spec.html#use-of-dynamic-types
Solidity and Vyper are the same in encoding arguments.