Rewards

Authors: Aloe Labs, Inc., Inspired by Yield Protocol

Implements logic for staking rewards

State Variables

_REWARDS_SLOT

bytes32 private constant _REWARDS_SLOT = keccak256("aloe.ii.rewards");

Functions

setRate

Sets the pool's rewards rate. May be 0.

function setRate(Storage storage store, uint160 accumulated, uint64 rate) internal;

Parameters

Name	Type	Description
`store`	`Storage`	The rewards storage pointer
`accumulated`	`uint160`	Up-to-date `poolState.accumulated`, i.e. the output of `_accumulate`
`rate`	`uint64`	The rewards rate, specified as [token units per second]. Keep between 10^17 and 10^28 token units per year for smooth operation -- between 0.1 and 10 billion tokens, assuming 18 decimals.

claim

function claim(
    Storage storage store,
    uint160 accumulated,
    address user,
    uint256 balance
) internal returns (uint96 earned);

updatePoolState

Ensures that changes in the pool's totalSupply don't mess up rewards accounting. Should be called anytime totalSupply changes.

Use Rewards.load() to easily obtain the first two arguments

function updatePoolState(Storage storage store, uint160 accumulated) internal;

Parameters

Name	Type	Description
`store`	`Storage`	The rewards storage pointer
`accumulated`	`uint160`	Up-to-date `poolState.accumulated`, i.e. the output of `_accumulate`

updateUserState

Tracks how much reward a user earned while holding a particular balance. Should be called anytime their balance changes.

Use Rewards.load() to easily obtain the first two arguments

function updateUserState(Storage storage store, uint160 accumulated, address user, uint256 balance) internal;

Parameters

Name	Type	Description
`store`	`Storage`	The rewards storage pointer
`accumulated`	`uint160`	Up-to-date `poolState.accumulated`, i.e. the output of `_accumulate`
`user`	`address`	The user whose balance (# of shares) is about to change
`balance`	`uint256`	The user's balance (# of shares) -- before it changes

previewUserState

function previewUserState(
    Storage storage store,
    uint160 accumulated,
    address user,
    uint256 balance
) internal view returns (UserState memory userState);

getRate

function getRate() internal view returns (uint64);

load

Returns arguments to be used in updatePoolState and updateUserState. No good semantic meaning here, just a coincidence that both functions need this information.

function load(uint256 totalSupply) internal view returns (Storage storage store, uint160 accumulator);

_accumulate

Accumulates rewards based on the current rate and time elapsed since last update

function _accumulate(PoolState memory poolState, uint256 totalSupply) private view returns (uint160);

_storage

Diamond-pattern-style storage getter

function _storage() private pure returns (Storage storage store);

Events

RewardsRateSet

event RewardsRateSet(uint64 rate);

RewardsClaimed

event RewardsClaimed(address indexed user, uint96 amount);

Structs

PoolState

struct PoolState {
    uint160 accumulated;
    uint32 lastUpdated;
    uint64 rate;
}

UserState

struct UserState {
    uint96 earned;
    uint160 checkpoint;
}

Storage

struct Storage {
    PoolState poolState;
    mapping(address => UserState) userStates;
}

Aloe II