Staker.sol: Cache shift amounts

[code423n4]

Handle

hickuphh3

Vulnerability details

Impact

The user's userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_long and userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_short are retrieved a number of times in _calculateAccumulatedFloat(). Caching these values would help save gas.

Note that block scoping is needed to avoid the stack too deep problem.

Recommended Mitigation Steps

function _calculateAccumulatedFloat() {
	// block scope for shiftAmount variable to avoid stack too deep
	{
		// Update the users balances
	  uint256 shiftAmount = userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_long[marketIndex][user];
	  if (shiftAmount > 0) {
	    amountStakedShort += ILongShort(longShort).getAmountSyntheticTokenToMintOnTargetSide(
	      marketIndex,
	      shiftAmount,
	      true,
	      stakerTokenShiftIndex_to_longShortMarketPriceSnapshotIndex_mapping[usersShiftIndex]
	    );
	
	    amountStakedLong -= shiftAmount;
	    userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_long[marketIndex][user] = 0;
	  }
	
	  shiftAmount = userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_short[marketIndex][user]
	  if (shiftAmount > 0) {
	    amountStakedLong += ILongShort(longShort).getAmountSyntheticTokenToMintOnTargetSide(
	      marketIndex,
	      shiftAmount,
	      false,
	      stakerTokenShiftIndex_to_longShortMarketPriceSnapshotIndex_mapping[usersShiftIndex]
	    );
	
	    amountStakedShort -= shiftAmount;
	    userNextPrice_amountStakedSyntheticToken_toShiftAwayFrom_short[marketIndex][user] = 0;
	  }
	}
	// end of block scoping

	// Save the users updated staked amounts
	...
}

[JasoonS]

Cool, makes sense!