mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
66 lines
2.3 KiB
Solidity
66 lines
2.3 KiB
Solidity
pragma solidity ^0.4.11;
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import './BasicToken.sol';
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import './ERC20.sol';
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/**
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* @title Standard ERC20 token
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*
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* @dev Implementation of the basic standard token.
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* @dev https://github.com/ethereum/EIPs/issues/20
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* @dev Based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
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*/
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contract StandardToken is ERC20, BasicToken {
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mapping (address => mapping (address => uint256)) allowed;
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/**
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* @dev Transfer tokens from one address to another
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* @param _from address The address which you want to send tokens from
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* @param _to address The address which you want to transfer to
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* @param _value uint256 the amout of tokens to be transfered
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*/
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function transferFrom(address _from, address _to, uint256 _value) {
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uint256 _allowance = allowed[_from][msg.sender];
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// Check is not needed because sub(_allowance, _value) will already throw if this condition is not met
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// if (_value > _allowance) throw;
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balances[_to] = balances[_to].add(_value);
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balances[_from] = balances[_from].sub(_value);
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allowed[_from][msg.sender] = _allowance.sub(_value);
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Transfer(_from, _to, _value);
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}
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/**
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* @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
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* @param _spender The address which will spend the funds.
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* @param _value The amount of tokens to be spent.
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*/
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function approve(address _spender, uint256 _value) {
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// To change the approve amount you first have to reduce the addresses`
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// allowance to zero by calling `approve(_spender, 0)` if it is not
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// already 0 to mitigate the race condition described here:
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// https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
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if ((_value != 0) && (allowed[msg.sender][_spender] != 0)) throw;
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allowed[msg.sender][_spender] = _value;
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Approval(msg.sender, _spender, _value);
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}
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/**
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* @dev Function to check the amount of tokens that an owner allowed to a spender.
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* @param _owner address The address which owns the funds.
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* @param _spender address The address which will spend the funds.
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* @return A uint256 specifing the amount of tokens still avaible for the spender.
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*/
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function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
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return allowed[_owner][_spender];
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}
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}
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