[midnight adapter] maturity bitmaps

[adhusson]

• code slightly easier to underestand
• buy gas cost is constant excluding accrual (not important)
• maturities are aligned to the hour
• prevent DOS with max ttm at buy is 10 years. So max accrual gas is ~1m gas, reached after 10 years without ping & 50 active maturity hours to go through. After 2 months without ping it's 135k gas.

[adhusson]

Could do this as well (it removes the duplication of accrueInterest logic)

Suggested change

	return (currentGrowth, _totalAssets);
	function accrueInterest() public returns (uint128, uint256) {
	if (lastUpdate != block.timestamp) {
	(currentGrowth, _totalAssets) = accrueInterestView();
	uint256 lastIndex = block.timestamp.zeroFloorSub(1).bitmapIndex();
	for (uint256 index = lastUpdate.bitmapIndex(); index < lastIndex; index++) {
	bitmaps[index] = 0;
	}
	uint256 nowBit = (block.timestamp - 1)/ 1 hours% 256 + 1;
	bitmaps[lastIndex] = (bitmaps[lastIndex] >> nowBit) << nowBit;
	lastUpdate = uint48(block.timestamp);
	}
	return (currentGrowth, _totalAssets);
	}

[adhusson]

This is the index of a bitmap. Small clash with collateralIndex in midnight which is a bit position.

[adhusson]

Closing for now as the complexity is not worth it compared to #921, and increase slot opening gas cost make it less interesting. Still in terms of O(n) it is the best on accrual insertion and deletion.