SwapPair Code Style Findings

SPR-01C: Inefficient Calculation of Domain Separator

Type	Severity	Location
Gas Optimization		SwapPair.sol:L479-L487

Description:

The DOMAIN_SEPARATOR of the contract is calculated and stored on each invocation of the permit function which is inefficient.

Example:

Copy
477function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external {
478    require(deadline >= block.timestamp, 'SwapPair: EXPIRED');
479    DOMAIN_SEPARATOR = keccak256(
480        abi.encode(
481            keccak256('EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)'),
482            keccak256(bytes(name)),
483            keccak256('1'),
484            block.chainid,
485            address(this)
486        )
487    );

Recommendation:

We advise a pattern similar to the draft-ERC20Permit contract of OpenZeppelin whereby the canonical DOMAIN_SEPARATOR (the one that is calculated with the chainid that the contract is deployed in) is cached in storage and is only re-calculated if the dynamic block.chainid differs from the one the original DOMAIN_SEPARATOR was calculated in. This will significantly reduce the gas cost of the permit function.

Alleviation:

The Xcaliswap team evaluated this exhibit but opted not to apply any changes for it in the current iteration of the protocol.

SPR-02C: Inexistent Error Messages

Type	Severity	Location
Code Style		SwapPair.sol:L114, L346, L533, L536

Description:

The linked require checks have no error messages explicitly defined.

Example:

Copy
114require(_unlocked == 1);

Recommendation:

We advise each to be set so to increase the legibility of the codebase and aid in validating the require checks' conditions.

Alleviation:

The Xcaliswap team evaluated this exhibit but opted not to apply any changes for it in the current iteration of the protocol.

SPR-03C: Loop Iterator Optimization

Type	Severity	Location
Gas Optimization		SwapPair.sol:L268

Description:

The linked for loop increments / decrements the iterator "safely" due to Solidity's built-in safe arithmetics(post - 0.8.X).

Example:

Copy
268for (uint i = 0; i < _prices.length; i++) {

Recommendation:

We advise the increment / decrement operation to be performed in an unchecked code block as the last statement within the for loop to optimize its execution cost.

Alleviation:

The Xcaliswap team evaluated this exhibit but opted not to apply any changes for it in the current iteration of the protocol.

SPR-04C: Repetitive Value Literal

Type	Severity	Location
Code Style		SwapPair.sol:L367, L368, L425

Description:

The linked value literal is repeated across the codebase multiple times.

Example:

Copy
367if (amount0In > 0) _update0(amount0In * fee / 1e6); // accrue fees for token0 and move them out of pool

Recommendation:

We advise it to be set to a constant variable instead optimizing the legibility of the codebase.

Alleviation:

The Xcaliswap team evaluated this exhibit but opted not to apply any changes for it in the current iteration of the protocol.