Min erc20 (WIP)

ERC20 Token standard written in solidity with different transfer behavior (Work in Progress)
Uses inline assembly to save a little bit on gas.

Main difference/Trade-off behavior

• Transfer function can't fail
• Transfer function sets the amount to min(_balances[msg.sender], value)
  • => either sends specified amount or max-balance (if amount > max-balance)

the min function uses inline assembly without using if branching:

function min(uint256 x, uint256 y) public pure returns (uint256) {
    assembly {
        x := xor(x,and(xor(y,x), add(not(slt(y,x)), 1)))
    }
    return x;
}

Implications

• As the transfer function can't fail anymore for amounts exceeding the balance, it needs to be communicated properly to an end user.
• Usability/Safety for the different transfer logic can be achieved again by a specific UI rather than the underlying contract source code.

E.g., error notice or input fields which show you that the amount >= your balance results always in the max value of your account.

• Example UI can be found in the frontend folder (WIP)

Gas Usage

forge test --match-contract gasTest --gas-report

| src/erc20.sol:ERC20 contract |                 |       |        |       |         |
|------------------------------|-----------------|-------|--------|-------|---------|
| Deployment Cost              | Deployment Size |       |        |       |         |
| 565252                       | 3635            |       |        |       |         |
| Function Name                | min             | avg   | median | max   | calls   |
| balanceOf                    | 2544            | 2544  | 2544   | 2544  | 2       |
| standardTransfer             | 23162           | 25239 | 25162  | 29962 | 36      |
| transfer                     | 22818           | 24895 | 24818  | 29618 | 36      |

forge test --match-contract gasTest --gas-report --optimize --optimizer-runs 3500

| src/erc20.sol:ERC20 contract |                 |       |        |       |         |
|------------------------------|-----------------|-------|--------|-------|---------|
| Deployment Cost              | Deployment Size |       |        |       |         |
| 645134                       | 4034            |       |        |       |         |
| Function Name                | min             | avg   | median | max   | calls   |
| balanceOf                    | 2543            | 2543  | 2543   | 2543  | 2       |
| standardTransfer             | 23082           | 25159 | 25082  | 29882 | 36      |
| transfer                     | 22750           | 24827 | 24750  | 29550 | 36      |