ButtonToken
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The ButtonToken is a rebasing wrapper for fixed balance ERC-20 tokens. Users can acccess this in on .
Users deposit the "underlying" (wrapped) tokens and are minted button (wrapper) tokens with elastic balances which change up or down when the value of the underlying token changes.
For example: Manny “wraps” 1 Ether when the price of Ether is $1800. Manny receives 1800 ButtonEther tokens in return. The overall value of their ButtonEther is the same as their original Ether, however each unit is now priced at exactly $1. The next day, the price of Ether changes to $1900. The ButtonEther system detects this price change, and rebases such that Manny’s balance is now 1900 ButtonEther tokens, still priced at $1 each.
The ButtonToken math is almost identical to Ampleforth's μFragments.
For AMPL, internal balances are represented using gons and
internal account balance _gonBalances[account]
internal supply scalar gonsPerFragment = TOTAL_GONS / _totalSupply
public balance _gonBalances[account] * gonsPerFragment
public total supply _totalSupply
In our case internal balances are stored as 'bits'.
underlying token unit price p_u = price / 10 ^ (PRICE_DECIMALS)
total underlying tokens _totalUnderlying
internal account balance _accountBits[account]
internal supply scalar _bitsPerToken = TOTAL_BITS / (MAX_UNDERLYING*p_u) = BITS_PER_UNDERLYING*(10^PRICE_DECIMALS)/price = PRICE_BITS / price
user's underlying balance _accountBits[account] / BITS_PER_UNDERLYING
public balance _accountBits[account] * _bitsPerToken
public total supply _totalUnderlying * p_u
validRecipient(address to)Validates that the address is a valid recipient for tokens:
Is not the 0 address
Is not the token contract's address
onAfterRebase()Modifier to perform a rebase before executing token transfers, deposits, or withdrawals. Refetches the latest price data and rebases the supply around the new price.
initialize(address underlying_, string name_, string symbol_, address oracle_) (public)Initializes the token contract with the given parameters.
updateOracle(address oracle_) (public)Updates the oracle to the new oracle address.
Only callable by the contract owner.
decimals() → uint8 (external)Get the number of decimals of precision for this token. This is derived from the decimals of the underlying token.
totalSupply() → uint256 (external)Get the current total supply of the token contract.
balanceOf(address account) → uint256 (external)Get the current balance of the user.
scaledTotalSupply() → uint256 (external)Get the current total supply of the token contract, scaled to the underlying amount. In other words, returns the total amount of collateral locked in the contract.
scaledBalanceOf(address account) → uint256 (external)Get the current balance of the user, scaled to the underlying amount.
allowance(address owner_, address spender) → uint256 (external)Returns the remaining number of tokens that spender will be allowed to spend on behalf of owner through transferFrom. This is zero by default.
totalUnderlying() → uint256 (external)Returns the number of underlying collateral tokens stored in the contract.
balanceOfUnderlying(address who) → uint256 (external)Returns the user's current balance in terms of the underlying collateral tokens.
underlyingToWrapper(uint256 uAmount) → uint256 (external)Returns the equivalent number of wrapper tokens for a given underlying amount.
wrapperToUnderlying(uint256 amount) → uint256 (external)Returns the equivalent number of underlying tokens for the given amount of wrapper tokens.
transfer(address to, uint256 amount) → bool (external)Moves amount tokens from the caller's account to to.
Returns a boolean value indicating whether the operation succeeded
transferAll(address to) → bool (external)Moves all of the caller's tokens to to.
Returns a boolean value indicating whether the operation succeeded
transferFrom(address from, address to, uint256 amount) → bool (external)Moves amount of tokens from from to to using the allowance mechanism.
Amount is deducted from the caller's allowance.
Returns a boolean value indicating whether the operation succeeded.
transferAllFrom(address from, address to) → bool (external)Moves all tokens from from to to using the allowance mechanism.
Returns a boolean value indicating whether the operation succeeded.
approve(address spender, uint256 amount) → bool (external)Sets amount as the allowance of spender over the caller's tokens.
Returns a boolean indicating whether the operatino succeeded
increaseAllowance(address spender, uint256 addedAmount) → bool (external)decreaseAllowance(address spender, uint256 subtractedAmount) → bool (external)rebase() (external)Fetch new price from the oracle and rebase the token's supply accordingly
mint(uint256 amount) → uint256 (external)Mint amount wrapper tokens, taking the required number of collateral tokens to do so.
mintFor(address to, uint256 amount) → uint256 (external)Mint amount wrapper tokens for to, taking the required number of collateral tokens to do so
burn(uint256 amount) → uint256 (external)Burn amount wrapper tokens, returns the equivalent value of collateral tokens to the caller.
burnTo(address to, uint256 amount) → uint256 (external)Burn amount wrapper tokens, returns the equivalent value of collateral tokens to to.
burnAll() → uint256 (external)Burn all wrapper tokens held by caller, returns equivalent value of collateral tokens to caller.
burnAllTo(address to) → uint256 (external)Burn all wrapper tokens held by caller, returns equivalent value of collateral tokens to to.
deposit(uint256 uAmount) → uint256 (external)Deposit uAmount collateral tokens, minting the equivalent value of wrapper tokens to the caller.
depositFor(address to, uint256 uAmount) → uint256 (external)Deposit uAmount collateral tokens, minting the equivalent value of wrapper tokens to to
withdraw(uint256 uAmount) → uint256 (external)Withdraw uAmount collateral tokens, minting the equivalent value of wrapper tokens to the caller.
withdrawTo(address to, uint256 uAmount) → uint256 (external)Withdraw uAmount collateral tokens, minting the equivalent value of wrapper tokens to to.
withdrawAll() → uint256 (external)Withdraw all collateral tokens from the contract.
withdrawAllTo(address to) → uint256 (external)Withdraw all collateral tokens from the contract, sending them to to.