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ERC-721B

The standard ERC721B1 was suggested as an improvement of ERC721 but without the drawbacks of the ERC721A such as integer overflow for collections over 5,000 items.

Transaction fee effectiveness

The standard allows users to save on transaction fees only when minting or burning tokens in batches.

Here's the original OpenZeppelin implementation of the internal _mint function:

function _mint(address to, uint256 tokenId) internal virtual {
    require(to != address(0), "ERC721: mint to the zero address");
    require(!_exists(tokenId), "ERC721: token already minted");

    _beforeTokenTransfer(address(0), to, tokenId, 1);

    // Check that tokenId was not minted by `_beforeTokenTransfer` hook
    require(!_exists(tokenId), "ERC721: token already minted");

    unchecked {
        // Will not overflow unless all 2**256 token ids are minted to the same owner.
        // Given that tokens are minted one by one, it is impossible in practice that
        // this ever happens. Might change if we allow batch minting.
        // The ERC fails to describe this case.
        _balances[to] += 1;
    }

    _owners[tokenId] = to;

    emit Transfer(address(0), to, tokenId);

    _afterTokenTransfer(address(0), to, tokenId, 1);
}

The same function in the ERC721B looks like this2:

function _mint(
    address to,
    // parameter removed and replaced with auto incrementing logic
    // uint256 tokenId,
    // additional parameter
    uint256 amount,
    // additional parameter
    bytes memory _data,
    // additional parameter
    bool safeCheck 
  ) private {
    // Instead of: `require(to != address(0), 
    // "ERC721: mint to the zero address");`
    if(amount == 0 || to == address(0)) revert InvalidCall();
    // Auto tokenId increment
    // Removes the `require(!_exists(tokenId), 
    // "ERC721: token already minted");`
    uint256 startTokenId = _lastTokenId + 1; 
    
    _beforeTokenTransfers(address(0), to, startTokenId, amount);
    
    unchecked {
      // - Additional storage operation + 5,000 gas
      // for each update
      _lastTokenId += amount;
      // balances are increased by the amount not +1
      // + SUBSTANTIAL ECNOMY HERE !!!
      _balances[to] += amount;
      // = Same as in standard ERC721
      _owners[startTokenId] = to;

      _afterTokenTransfers(address(0), to, startTokenId, amount);

      uint256 updatedIndex = startTokenId;
      uint256 endIndex = updatedIndex + amount;

      if (safeCheck && to.code.length > 0) {
        do {
          emit Transfer(address(0), to, updatedIndex);
          // Checks if a contract implements ERC721Receiver
          if (!_checkOnERC721Received(address(0), to, updatedIndex++, _data))
            revert ERC721ReceiverNotReceived();
        } while (updatedIndex != endIndex);
        return;
      }

      do {
        emit Transfer(address(0), to, updatedIndex++);
      } while (updatedIndex != endIndex);
    }
  }

ERC721B Extensions

FunctionalityERC721B
tokenURI(uint256 tokenId)
baseTokenURI()
_setBaseURI(string memory uri)		ERC721BBaseTokenURI.sol
ownerOf(uint256 tokenId)
totalSupply()
burn(uint256 tokenId)
_exists(uint256 tokenId)		ERC721BBurnable.sol
contractURI()ERC721BContractURIStorage.sol
_beforeTokenTransfers(address from,address to,uint256 startTokenId,uint256 amount)ERC721BPausable.sol
isTransferConsumed(address from,address to,uint256 tokenId,uint256 nonce)
signedTransferFrom(address from,address to,uint256 tokenId,uint256 nonce,bytes memory signed)
signedTransferFrom(address from,address to,uint256 tokenId,uint256 nonce,bytes memory signed,bytes memory _data)		ERC721BSignedTransfer.sol
tokenURI(uint256 tokenId)
staticTokenURI(uint256 tokenId)
_setTokenURI(uint256 tokenId, string memory _tokenURI)		ERC721BStaticTokenURI.sol
name()
symbol()		ERC721Metadata.sol

Drawbacks:

  1. TX fee improvements only for batch minting
  2. Automatic tokenId handling (requires logic rewriting for target mapped contracts to accept tokens with native ID)

Summary:

After carefully studying the above implementation we see room for further TX fee improvements which we will describe in our following documents.

  1. https://github.com/badbabybearbots/ERC721B↩
  2. Original inline comments were replaced with XP.NETWORK explanations.↩