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Rebase Orchestrator (#150)
* Orchestrator and first set of tests * tests and origin protection * downstream revert protection * review feedback * Check for extra transactions * Remove configurability of transaction gwei amount Co-authored-by: Brandon Iles <[email protected]>
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‎.eslintrc.js

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@@ -50,7 +50,7 @@ module.exports = {
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// project-specific
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"rebase", "gons", "frg", "rng", "blockchain", "minlot",
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"redemptions", "rebased", "ganache", "ethclient",
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"bytecode", "Binance", "ethereum", "opcode", "cpi", "ampleforth",
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"bytecode", "Binance", "ethereum", "opcode", "cpi", "ampleforth", "orchestrator",
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// names
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"nithin",

‎contracts/Orchestrator.sol

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pragma solidity 0.4.24;
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import "openzeppelin-eth/contracts/ownership/Ownable.sol";
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import "./UFragmentsPolicy.sol";
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/**
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* @title Orchestrator
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* @notice The orchestrator is the main entry point for rebase operations. It coordinates the policy
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* actions with external consumers.
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*/
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contract Orchestrator is Ownable {
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struct Transaction {
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address destination;
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bytes data;
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bool enabled;
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}
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event TransactionFailed(address indexed destination, uint index, bytes data);
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// Stable ordering is not guaranteed.
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Transaction[] public transactions;
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UFragmentsPolicy public policy;
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/**
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* @param policy_ Address of the UFragments policy.
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*/
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constructor(address policy_) public {
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Ownable.initialize(msg.sender);
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policy = UFragmentsPolicy(policy_);
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}
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/**
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* @notice Main entry point to initiate a rebase operation.
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* The Orchestrator calls rebase on the policy and notifies downstream applications.
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* Contracts are guarded from calling, to avoid flash loan attacks on liquidity
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* providers.
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* If a transaction in the transaction list reverts, it is swallowed and the remaining
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* transactions are executed.
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*/
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function rebase()
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external
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{
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require(msg.sender == tx.origin); // solhint-disable-line avoid-tx-origin
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policy.rebase();
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for (uint i = 0; i < transactions.length; i++) {
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Transaction storage t = transactions[i];
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if (t.enabled) {
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bool result =
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externalCall(t.destination, 0, t.data.length, t.data);
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if (!result) {
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emit TransactionFailed(t.destination, i, t.data);
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}
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}
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}
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}
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/**
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* @notice Adds a transaction that gets called for a downstream receiver of rebases
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* @param destination Address of contract destination
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* @param data Transaction data payload
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*/
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function addTransaction(address destination, bytes data)
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external
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onlyOwner
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{
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transactions.push(Transaction({
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destination: destination,
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data: data,
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enabled: true
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}));
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}
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/**
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* @param index Index of transaction to remove.
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* Transaction ordering may have changed since adding.
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*/
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function removeTransaction(uint index)
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external
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onlyOwner
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{
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require(index < transactions.length, "index out of bounds");
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if (index < transactions.length - 1) {
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transactions[index] = transactions[transactions.length - 1];
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}
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delete transactions[transactions.length - 1];
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transactions.length--;
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}
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/**
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* @param index Index of transaction. Transaction ordering may have changed since adding.
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* @param enabled True for enabled, false for disabled.
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*/
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function setTransactionEnabled(uint index, bool enabled)
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external
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onlyOwner
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{
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require(index < transactions.length, "index must be in range of stored tx list");
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transactions[index].enabled = enabled;
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}
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/**
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* @return Number of transactions, both enabled and disabled, in transactions list.
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*/
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function transactionsLength()
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external
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view
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returns (uint256)
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{
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return transactions.length;
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}
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/**
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* @dev wrapper to call the encoded transactions on downstream consumers.
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* @param destination Address of destination contract.
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* @param transferValueWei ETH value to send, in wei.
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* @param dataLength Size of data param.
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* @param data The encoded data payload.
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* @return True on success
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*/
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function externalCall(address destination, uint transferValueWei, uint dataLength, bytes data)
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internal
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returns (bool)
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{
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bool result;
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assembly { // solhint-disable-line no-inline-assembly
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// "Allocate" memory for output
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// (0x40 is where "free memory" pointer is stored by convention)
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let outputAddress := mload(0x40)
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// First 32 bytes are the padded length of data, so exclude that
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let dataAddress := add(data, 32)
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result := call(
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// 34710 is the value that solidity is currently emitting
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// It includes callGas (700) + callVeryLow (3, to pay for SUB)
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// + callValueTransferGas (9000) + callNewAccountGas
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// (25000, in case the destination address does not exist and needs creating)
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sub(gas, 34710),
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destination,
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transferValueWei,
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dataAddress,
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dataLength, // Size of the input (in bytes). This is what fixes the padding problem
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outputAddress,
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0 // Output is ignored, therefore the output size is zero
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)
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}
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return result;
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}
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}

‎contracts/UFragmentsPolicy.sol

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@@ -82,17 +82,22 @@ contract UFragmentsPolicy is Ownable {
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// MAX_SUPPLY = MAX_INT256 / MAX_RATE
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uint256 private constant MAX_SUPPLY = ~(uint256(1) << 255) / MAX_RATE;
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// This module orchestrates the rebase execution and downstream notification.
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address public orchestrator = address(0x0);
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modifier onlyOrchestrator() {
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require(msg.sender == orchestrator);
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_;
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}
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/**
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* @notice Any EOA address can call this function to initiate a new rebase operation, provided
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* more than the minimum time period has elapsed.
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* Contracts are guarded from calling, to avoid flash loan attacks on liquidity
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* providers.
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* @notice Initiates a new rebase operation, provided the minimum time period has elapsed.
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*
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* @dev The supply adjustment equals (_totalSupply * DeviationFromTargetRate) / rebaseLag
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* Where DeviationFromTargetRate is (MarketOracleRate - targetRate) / targetRate
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* and targetRate is CpiOracleRate / baseCpi
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*/
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function rebase() external {
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require(msg.sender == tx.origin); // solhint-disable-line avoid-tx-origin
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function rebase() external onlyOrchestrator {
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require(inRebaseWindow());
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// This comparison also ensures there is no reentrancy.
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marketOracle = marketOracle_;
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}
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/**
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* @notice Sets the reference to the orchestrator.
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* @param orchestrator_ The address of the orchestrator contract.
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*/
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function setOrchestrator(address orchestrator_)
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external
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onlyOwner
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{
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orchestrator = orchestrator_;
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}
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/**
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* @notice Sets the deviation threshold fraction. If the exchange rate given by the market
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* oracle is within this fractional distance from the targetRate, then no supply

‎contracts/mocks/ConstructorRebaseCallerContract.sol

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@@ -1,13 +1,13 @@
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pragma solidity 0.4.24;
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import "../UFragmentsPolicy.sol";
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import "../Orchestrator.sol";
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contract ConstructorRebaseCallerContract {
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constructor(address policy) public {
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constructor(address orchestrator) public {
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// Take out a flash loan.
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// Do something funky...
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UFragmentsPolicy(policy).rebase(); // should fail
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Orchestrator(orchestrator).rebase(); // should fail
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// pay back flash loan.
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}
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}

‎contracts/mocks/MockDownstream.sol

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pragma solidity 0.4.24;
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import "./Mock.sol";
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contract MockDownstream is Mock {
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function updateNoArg() external returns (bool) {
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emit FunctionCalled("MockDownstream", "updateNoArg", msg.sender);
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uint256[] memory uintVals = new uint256[](0);
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int256[] memory intVals = new int256[](0);
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emit FunctionArguments(uintVals, intVals);
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return true;
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}
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function updateOneArg(uint256 u) external {
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emit FunctionCalled("MockDownstream", "updateOneArg", msg.sender);
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uint256[] memory uintVals = new uint256[](1);
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uintVals[0] = u;
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int256[] memory intVals = new int256[](0);
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emit FunctionArguments(uintVals, intVals);
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}
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function updateTwoArgs(uint256 u, int256 i) external {
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emit FunctionCalled("MockDownstream", "updateTwoArgs", msg.sender);
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uint256[] memory uintVals = new uint256[](1);
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uintVals[0] = u;
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int256[] memory intVals = new int256[](1);
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intVals[0] = i;
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emit FunctionArguments(uintVals, intVals);
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}
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function reverts() external {
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emit FunctionCalled("MockDownstream", "reverts", msg.sender);
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uint256[] memory uintVals = new uint256[](0);
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int256[] memory intVals = new int256[](0);
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emit FunctionArguments(uintVals, intVals);
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require(false, "reverted");
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}
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}

‎contracts/mocks/MockUFragmentsPolicy.sol

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pragma solidity 0.4.24;
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import "./Mock.sol";
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contract MockUFragmentsPolicy is Mock {
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function rebase() external {
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emit FunctionCalled("UFragmentsPolicy", "rebase", msg.sender);
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}
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}

‎contracts/mocks/RebaseCallerContract.sol

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pragma solidity 0.4.24;
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import "../UFragmentsPolicy.sol";
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import "../Orchestrator.sol";
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contract RebaseCallerContract {
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function callRebase(address policy) public returns (bool) {
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function callRebase(address orchestrator) public returns (bool) {
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// Take out a flash loan.
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// Do something funky...
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UFragmentsPolicy(policy).rebase(); // should fail
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Orchestrator(orchestrator).rebase(); // should fail
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// pay back flash loan.
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return true;
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}

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