DSPause

1. Summary
DSPause allows authorized users to schedule function calls that can only be executed once some predetermined waiting period has elapsed. The configurable delay attribute sets the minimum wait time between scheduling and executing a transaction.
2. Contract Variables & Functions
Variables
scheduledTransactions[hashedTx: bytes32] - mapping with all scheduled transactions. A 
hashedTx consists of an address usr to delegatecall into, the expected codehash of usr, calldata to use and the first possible time of execution
proxy - the proxy contract that will execute scheduledTransactions in an isolated environment. It can only be called by DSPause
delay - the delay applied to every scheduledTransaction
currentlyScheduledTransactions - the current number of concurrently scheduled transactions
maxScheduledTransactions - the max number of transactions that can be scheduled at the same time
MAX_DELAY - the maximum delay for a transaction from the moment it is scheduled
DS_PAUSE_TYPE - the type of the DSPause contract (can be BASIC or PROTEST)
Modifiers
isDelayed - checks if msg.sender is DSPause itself
Functions
setOwner(owner: address) - set a new contract owner. Overriden from DSAuth
setAuthority(authority: DSAuthority) - set an authority contract. Overriden from DSAuth
setDelay(delay: uint256) - set a delay applied to all scheduledTransactions
scheduleTransaction(usr:address, codeHash: bytes32, parameters: bytes, earliestExecutionTime: uint) - schedule a new transaction by providing usr, usr's codehash, the calldata and the first possible time of execution
scheduleTransaction(usr: address, codeHash: bytes32, parameters: bytes, earliestExecutionTime: uint, description: string) - schedule a new transaction and attach a description to it
attachTransactionDescription(usr: address, codeHash: bytes32, parameters: bytes, earliestExecutionTime: uint, description: string) - attach a description for an already scheduled transaction
abandonTransaction(usr:address, codeHash: bytes32, parameters: bytes, earliestExecutionTime: uint)- delete a scheduled transaction
executeTransaction(usr:address, codeHash: bytes32, parameters: bytes, earliestExecutionTime: uint)- execute a scheduled transaction. Throws if the scheduledTransaction's delay has not yet passed
Events
SetDelay - emitted when the delay is changed. Contains:
delay - the new delay
ScheduleTransaction - emitted when a new transaction is scheduled. Contains:
sender - the msg.sender that scheduled the transaction
usr - the target contract
codeHash - the code hash of usr
parameters - parameters for the transaction
earliestExecutionTime - earliest time when the transaction can be executed
AbandonTransaction - emitted when governance abandons a previously scheduled transaction. Contains:
sender - the msg.sender that scheduled the transaction
usr - the target contract
codeHash - the code hash of usr
parameters - parameters for the transaction
earliestExecutionTime - earliest time when the transaction can be executed
ExecuteTransaction - emitted when a transaction is executed. Contains:
sender - the msg.sender that scheduled the transaction
usr - the target contract
codeHash - the code hash of usr
parameters - parameters for the transaction
earliestExecutionTime - earliest time when the transaction can be executed
AttachTransactionDescription - emitted when governance attaches a description to a scheduled transaction. Contains:
sender - the msg.sender that scheduled the transaction
usr - the target contract
codeHash - the code hash of usr
parameters - parameters for the transaction
earliestExecutionTime - earliest time when the transaction can be executed
description - the transaction description
3. Walkthrough
DSPause is designed to be used as a component in a governance system, to give affected parties time to respond to decisions. If those affected by governance decisions have e.g. exit or veto rights, then the pause can serve as an effective check on governance power.
Scheduled Transactions
A scheduledTransaction describes a single delegatecall operation and a unix timestamp earliestExecutionTime before which it cannot be executed.
A scheduledTransaction consists of:
usr: address to delegatecall into
codeHash: the expected codehash of usr
parameters: calldata to use
earliestExecutionTime: first possible time of execution (as seconds since unix epoch)
Each scheduled tx has a unique id, defined as keccack256(abi.encode(usr, codeHash, parameters, earliestExecutionTime))
Transaction Execution
In order to protect the internal storage of the pause from malicious writes during scheduledTransaction execution, we perform the actual delegatecall operation in a seperate contract with an isolated storage context (DSPauseProxy). Each pause has it's own individual proxy.
This means that scheduledTransactions are executed with the identity of the proxy, and when integrating the pause into some auth scheme, you probably want to trust the pause's proxy and not the pause itself.
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Contents

1. Summary

2. Contract Variables & Functions

3. Walkthrough

Scheduled Transactions

Transaction Execution