Update: ERC721A has now integrated this optimization. Along with using packed uint256, these optimizations are obsolete!
Bridging the optimality-gap in ERC721A in a realistic minting setup.
- Internally,
tokenDatais passed as storage instead of memory. - Keeps track of whether the next token data has already been set before, so that we don't have to check it (1 cold sload) on every transfer for all eternity.
- Saves (warm) sload on variables such as
collectionSizeandmaxPerWallet.
Further optimization could be achieved by storing the number of minted nfts in a certain batch and then back-calculating if a certain tokenId is the last in the batch. I.e. if A mints 5 ids, A 0 0 0 0 is stored. Now, if we transfer the last id in the batch, we know that the token following that one will have to be explicitly set, so we can skip an sload check.
| Function | Gas |
|---|---|
| test_mint1_ERC721A() | 59669 |
| test_mint1_ERC721AX() | 59355 |
| test_mint5_ERC721A() | 67508 |
| test_mint5_ERC721AX() | 67164 |
| test_transferFrom1_ERC721A() | 53562 |
| test_transferFrom1_ERC721AX() | 49402 |
| test_transferFrom2_ERC721A() | 73843 |
| test_transferFrom2_ERC721AX() | 72324 |
| test_transferFrom3_ERC721A() | 121225 |
| test_transferFrom3_ERC721AX() | 108486 |
test_transferFrom2 is when the optimization regarding nextTokenDataSet is not in effect.
forge snapshot --match-contract GasTest