collateral check

Overview

• cache

• updateState

• get user's AToken balance + amount to withdraw

• validateWithdraw: confirm user has sufficient balance and asset isActive

• updateInterestRates

• collateral check

• burn ATokens

• Ensure existing loans are collateralized

Interest rates are updated to account for the withdrawal of deposits, and therefore the reduction of supply. See .updateInterestRates

isUsingCollateral

• Transaction reverts on invalid reserveIndex

Let's examine the bitwise manipulations with an example. In this example, we assume six bits for simplicity, w.r.t to self.data

Example: Check if the user has been using the reserve at index 2 as collateral:

It the result of the bitwise operations is not equal to 0, the function would return true. This indicates that the user has been using the reserve at reserveIndex = 2 as collateral.

setUsingAsCollateral

Set the collateral bit for a specific asset to either 0 or 1, depending on bool usingAsCollateral.

(reserveIndex << 1) + 1

• This bitwise operation doubles the index and increments it by 1

• Creates the necessary offset to manipulate the relevant bits to the asset of specified index

• For more in-depth explanation see: isUsingCollateral

bit = 1 << offset

If usingAsCollateral is true, indicating that the reserve should be marked as used for collateral,

• bitwise OR operation between data and the bit value (self.data |= bit).

• sets the corresponding bit in the self.data variable to 1

If usingAsCollateral is false, indicating that the reserve should NOT be marked as collateral

• bitwise AND operation between data and the bit value (self.data &= bit).

• sets the corresponding bit in the self.data variable to 0