Yul721

• ERC721 contract written entirely in assembly, with custom storage mappings.
• Why? For fun and learning -- NOT intended to be used in production.
• Saves ~150 gas on mints compared to solmate/erc721

Assumptions

• Edition size is less than 268431360 and all tokenId's are between 0-268431359
• Token name and symbol are both less than 32 bytes/characters
• name() and symbol() will not be used except for display purposes since they're not memory safe
• No more than the first 4095 slots are used by inheriting contracts

Custom storage layout

• name: 0xb4deace9b1788ce1b03518da303be35696899d14b9f97084f0acb409d7135d4f
• symbol: 0x7d69ccd04f2a4cdb55d8c11fc025a501f1d8824144c5020daba01cb5bd77c117
• ownerOf: 0x1000-0xFFFFFFF
  • tokenId must be bound to max size of 0xFFFEFFF to prevent slot overwrite attack
• getApproved: 0x10000000-0x1FFFEFFF
  • tokenId must be bound to max size of 0xFFFEFFF to prevent slot overwrite attack
• balanceOf: owner address << 96
• isApprovedForAll: keccak(address owner, address spender)

Todo (feel free to submit a PR)

• safeMint/safeTransfer
• Further gas optimizations