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
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pragma solidity ^0.4.11;
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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 to limit token
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* transferability for different events. It is intended to be used as a base class for other token
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* 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 base class is
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* 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, uint256 _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 The address that will recieve the tokens.
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* @param _value The amount of tokens to be transferred.
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*/
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function transfer(address _to, uint256 _value) canTransfer(msg.sender, _value) {
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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 The address that will send the tokens.
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* @param _to The address that will recieve the tokens.
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* @param _value The amount of tokens to be transferred.
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*/
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function transferFrom(address _from, address _to, uint256 _value) canTransfer(_from, _value) {
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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 the
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* 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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