Pack structs tightly

[code423n4]

Handle

pauliax

Vulnerability details

Impact

Gas efficiency can be achieved by tightly packing the struct. Struct variables are stored in 32 bytes each so you can group smaller types to occupy less storage. For example, startedAt or boughtAt in Auction struct hold block.number so realistically this does not need uint256 and you can consider storing it in lower type. You can read more here: https://fravoll.github.io/solidity-patterns/tight_variable_packing.html or in the official documentation: https://docs.soliditylang.org/en/v0.4.21/miscellaneous.html

Recommended Mitigation Steps

Search for an optimal size and order of structs to reduce gas usage.