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61 lines
2.1 KiB
61 lines
2.1 KiB
pragma solidity ^0.4.8;
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import "./ERC20.sol";
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/**
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* @title LimitedTransferToken
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* @dev LimitedTransferToken defines the generic interface and the implementation
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to limit token transferability for different events.
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It is intended to be used as a base class for other token contracts.
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LimitedTransferToken has been designed to allow for different limiting factors,
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this can be achieved by recursively calling super.transferableTokens() until the
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base class is hit. For example:
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function transferableTokens(address holder, uint64 time) constant public returns (uint256) {
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return min256(unlockedTokens, super.transferableTokens(holder, time));
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}
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A working example is VestedToken.sol:
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https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/token/VestedToken.sol
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*/
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contract LimitedTransferToken is ERC20 {
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/**
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* @dev Checks whether it can transfer or otherwise throws.
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*/
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modifier canTransfer(address _sender, uint _value) {
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if (_value > transferableTokens(_sender, uint64(now))) throw;
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_;
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}
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/**
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* @dev Checks modifier and allows transfer if tokens are not locked.
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* @param _to address The address that will recieve the tokens
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* @param _value uint The amount of tokens to be transfered
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*/
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function transfer(address _to, uint _value) canTransfer(msg.sender, _value) {
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return super.transfer(_to, _value);
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}
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/**
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* @dev Checks modifier and allows transfer if tokens are not locked.
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* @param _from address The address that will send the tokens.
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* @param _to address The address that will recieve the tokens.
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* @param _value uint The amount of tokens to be transfered.
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*/
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function transferFrom(address _from, address _to, uint _value) canTransfer(_from, _value) {
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return super.transferFrom(_from, _to, _value);
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}
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/**
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* @dev Default transferable tokens function returns all tokens for a holder (no limit).
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* @dev Overwriting transferableTokens(address holder, uint64 time) is the way to provide
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the specific logic for limiting token transferability for a holder over time.
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*/
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function transferableTokens(address holder, uint64 time) constant public returns (uint256) {
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return balanceOf(holder);
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}
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}
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