114 lines
2.7 KiB
Solidity
114 lines
2.7 KiB
Solidity
pragma solidity ^0.4.23;
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import "./ERC20Token.sol";
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contract StandardToken is ERC20Token {
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uint256 private supply;
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mapping (address => uint256) balances;
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mapping (address => mapping (address => uint256)) allowed;
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constructor() internal { }
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function transfer(
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address _to,
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uint256 _value
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)
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external
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returns (bool success)
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{
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return transfer(msg.sender, _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) returns (bool) {
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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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require((_value == 0) || (allowed[msg.sender][_spender] == 0));
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allowed[msg.sender][_spender] = _value;
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Approval(msg.sender, _spender, _value);
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return true;
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}
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function transferFrom(
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address _from,
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address _to,
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uint256 _value
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)
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external
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returns (bool success)
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{
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if (balances[_from] >= _value &&
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allowed[_from][msg.sender] >= _value &&
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_value > 0) {
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allowed[_from][msg.sender] -= _value;
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return transfer(_from, _to, _value);
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} else {
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return false;
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}
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}
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function allowance(address _owner, address _spender)
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external
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view
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returns (uint256 remaining)
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{
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return allowed[_owner][_spender];
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}
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function balanceOf(address _owner)
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external
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view
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returns (uint256 balance)
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{
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return balances[_owner];
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}
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function totalSupply()
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external
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view
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returns(uint256 currentTotalSupply)
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{
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return supply;
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}
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function mint(
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address _to,
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uint256 _amount
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)
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internal
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{
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balances[_to] += _amount;
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supply += _amount;
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emit Transfer(0x0, _to, _amount);
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}
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function transfer(
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address _from,
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address _to,
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uint256 _value
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)
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internal
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returns (bool success)
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{
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if (balances[_from] >= _value && _value > 0) {
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balances[_from] -= _value;
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balances[_to] += _value;
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emit Transfer(_from, _to, _value);
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return true;
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} else {
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return false;
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}
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}
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}
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