Gas Optimizations

[code423n4]

Implement loops more efficiently

Caching the length saves gas. Moreover not assigning the default value 0 to i save gas;

Reference implementation

uint256 len = array.length;

for (uint256; i < len; ++i) {

// Operations

}

Scope:

./core/LensHub.sol:541:        for (uint256 i = 0; i < vars.datas.length; ++i) {
./core/modules/follow/ApprovalFollowModule.sol:41:        for (uint256 i = 0; i < addresses.length; ++i) {
./core/modules/follow/ApprovalFollowModule.sol:66:            for (uint256 i = 0; i < addresses.length; ++i) {
./core/modules/follow/ApprovalFollowModule.sol:128:        for (uint256 i = 0; i < toCheck.length; ++i) {
./libraries/InteractionLogic.sol:47:        for (uint256 i = 0; i < profileIds.length; ++i) {
./libraries/PublishingLogic.sol:403:        for (uint256 i = 0; i < byteHandle.length; ++i) {

For uint use != 0 rather than > 0

It costs less gas to do so.

Scope:

./core/base/ERC721Time.sol:135:            bytes(baseURI).length > 0 ? string(abi.encodePacked(baseURI, tokenId.toString())) : '';
./core/modules/follow/ApprovalFollowModule.sol:64:        if (data.length > 0) {

Do not assign default values to save gas

Scope:

uint256 x; costs less gas then uint256 x = 0;.

./core/FollowNFT.sol:120:        uint256 lower = 0;
./core/FollowNFT.sol:162:        uint256 lower = 0;
./upgradeability/VersionedInitializable.sol:29:    uint256 private lastInitializedRevision = 0;

Use bit-shift to save gas rather than dividing by 2

Scope:

./core/FollowNFT.sol:134:            uint256 center = upper - (upper - lower) / 2;
./core/FollowNFT.sol:176:            uint256 center = upper - (upper - lower) / 2;
./core/LensHub.sol:27: *      2. Almost every event in the protocol emits the current block timestamp, reducing the need to fetch it manually.
./core/base/ERC721Time.sol:20: * 2. Constructor replaced with an initializer.
./core/modules/ModuleGlobals.sol:109:        if (newTreasuryFee >= BPS_MAX / 2) revert Errors.InitParamsInvalid();

Use increment, when possible

In the code base += 1 is used, but using preincrement ++ is cheaper. (Same applies for substraction)

Scope:

./core/base/ERC721Time.sol:348:        _balances[to] += 1;
./core/base/ERC721Time.sol:404:        _balances[to] += 1;
./core/base/ERC721Time.sol:373:        _balances[owner] -= 1;

./core/base/ERC721Time.sol:373:        _balances[owner] -= 1;
./core/base/ERC721Time.sol:403:        _balances[from] -= 1;

[Zer0dot]

Caching is included in lens-protocol/core#80, the rest, although valid except for the zero initialization (which is handled by the optimizer now afaik), we won't be taking any action on.