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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))) throw;
_;
}
/**
* @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);
}
}
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