mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
58 lines
2.2 KiB
Solidity
58 lines
2.2 KiB
Solidity
pragma solidity ^0.4.11;
|
|
|
|
import "./ERC20.sol";
|
|
|
|
/**
|
|
* @title LimitedTransferToken
|
|
* @dev LimitedTransferToken defines the generic interface and the implementation to limit token
|
|
* transferability for different events. It is intended to be used as a base class for other token
|
|
* contracts.
|
|
* LimitedTransferToken has been designed to allow for different limiting factors,
|
|
* this can be achieved by recursively calling super.transferableTokens() until the base class is
|
|
* hit. For example:
|
|
* function transferableTokens(address holder, uint64 time) view public returns (uint256) {
|
|
* return min256(unlockedTokens, super.transferableTokens(holder, time));
|
|
* }
|
|
* A working example is VestedToken.sol:
|
|
* https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/VestedToken.sol
|
|
*/
|
|
|
|
contract LimitedTransferToken is ERC20 {
|
|
|
|
/**
|
|
* @dev Checks whether it can transfer or otherwise throws.
|
|
*/
|
|
modifier canTransfer(address _sender, uint256 _value) {
|
|
if (_value > transferableTokens(_sender, uint64(now))) revert();
|
|
_;
|
|
}
|
|
|
|
/**
|
|
* @dev Checks modifier and allows transfer if tokens are not locked.
|
|
* @param _to The address that will receive the tokens.
|
|
* @param _value The amount of tokens to be transferred.
|
|
*/
|
|
function transfer(address _to, uint256 _value) canTransfer(msg.sender, _value) public {
|
|
super.transfer(_to, _value);
|
|
}
|
|
|
|
/**
|
|
* @dev Checks modifier and allows transfer if tokens are not locked.
|
|
* @param _from The address that will send the tokens.
|
|
* @param _to The address that will receive the tokens.
|
|
* @param _value The amount of tokens to be transferred.
|
|
*/
|
|
function transferFrom(address _from, address _to, uint256 _value) public canTransfer(_from, _value) {
|
|
super.transferFrom(_from, _to, _value);
|
|
}
|
|
|
|
/**
|
|
* @dev Default transferable tokens function returns all tokens for a holder (no limit).
|
|
* @dev Overwriting transferableTokens(address holder, uint64 time) is the way to provide the
|
|
* specific logic for limiting token transferability for a holder over time.
|
|
*/
|
|
function transferableTokens(address holder, uint64 time) view public returns (uint256) {
|
|
return balanceOf(holder);
|
|
}
|
|
}
|