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Standard Token Contract on Ethereum
//Most, basic default, standardised Token contract.
//Based on standardised APIs & slightly extended. https://github.com/ethereum/wiki/wiki/Standardized_Contract_APIs
//adds AddressApproval & AddressApprovalOnce events
//approve & approveOnce works on premise that approved always takes precedence.
//adds unapprove to basic coin interface.
contract Coin {
function sendCoin(uint _value, address _to) returns (bool _success) {}
function sendCoinFrom(address _from, uint _value, address _to) returns (bool _success) {}
function coinBalance() constant returns (uint _r) {}
function coinBalanceOf(address _addr) constant returns (uint _r) {}
function approve(address _addr) {}
function approveOnce(address _addr, uint256 _maxValue) {}
function unapprove(address _addr) {}
function isApproved(address _proxy) constant returns (bool _r) {}
function isApprovedFor(address _target, address _proxy) constant returns (bool _r) {}
}
contract Token is Coin {
function Token(uint _initialAmount) {
balances[msg.sender] = _initialAmount;
}
event CoinTransfer(address indexed from, address indexed to, uint256 value);
event AddressApproval(address indexed from, address indexed to, bool result);
event AddressApprovalOnce(address indexed from, address indexed to, uint256 value);
function sendCoin(uint _value, address _to) returns (bool _success) {
if (balances[msg.sender] >= _value) {
balances[msg.sender] -= _value;
balances[_to] += _value;
CoinTransfer(msg.sender, _to, _value);
return true;
} else { return false; }
}
function sendCoinFrom(address _from, uint _value, address _to) returns (bool _success) {
if (balances[_from] >= _value) {
bool transfer = false;
if(approved[_from][msg.sender]) {
transfer = true;
} else {
if(_value < approved_once[_from][msg.sender]) {
transfer = true;
approved_once[_from][msg.sender] = 0; //reset
}
}
if(transfer == true) {
balances[_from] -= _value;
balances[_to] += _value;
CoinTransfer(_from, _to, _value);
return true;
} else { return false; }
}
}
function coinBalance() constant returns (uint _r) {
return balances[msg.sender];
}
function coinBalanceOf(address _addr) constant returns (uint _r) {
return balances[_addr];
}
function approve(address _addr) {
approved[msg.sender][_addr] = true;
AddressApproval(msg.sender, _addr, true);
}
function approveOnce(address _addr, uint256 _maxValue) {
approved_once[msg.sender][_addr] = _maxValue;
AddressApprovalOnce(msg.sender, _addr, _maxValue);
}
function unapprove(address _addr) {
approved[msg.sender][_addr] = false;
approved_once[msg.sender][_addr] = 0;
AddressApproval(msg.sender, _addr, false);
AddressApprovalOnce(msg.sender, _addr, 0);
}
function isApproved(address _proxy) constant returns (bool _r) {
if(approved[msg.sender][_proxy] == true || approved_once[msg.sender][_proxy] > 0) {
return true;
}
}
function isApprovedFor(address _target, address _proxy) constant returns (bool _r) {
if(approved[_target][_proxy] == true || approved_once[_target][_proxy] > 0) {
return true;
}
}
mapping (address => uint) public balances;
mapping (address => mapping (address => bool)) public approved;
mapping (address => mapping (address => uint256)) public approved_once;
}
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