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pragma solidity ^0.4.8; | |
contract Token { | |
event Transfer(address indexed from, address indexed to, uint value); | |
event Approval( address indexed owner, address indexed spender, uint value); | |
mapping( address => uint ) _balances; | |
mapping( address => mapping( address => uint ) ) _approvals; | |
uint public _supply; | |
function Token( uint initial_balance ) { | |
_balances[msg.sender] = initial_balance; | |
_supply = initial_balance; | |
} | |
function totalSupply() constant returns (uint supply) { | |
return _supply; | |
} | |
function balanceOf( address who ) constant returns (uint value) { | |
return _balances[who]; | |
} | |
function transfer( address to, uint value) returns (bool ok) { | |
if( _balances[msg.sender] < value ) { | |
throw; | |
} | |
if( !safeToAdd(_balances[to], value) ) { | |
throw; | |
} | |
_balances[msg.sender] -= value; | |
_balances[to] += value; | |
Transfer( msg.sender, to, value ); | |
return true; | |
} | |
function transferFrom( address from, address to, uint value) returns (bool ok) { | |
// if you don't have enough balance, throw | |
if( _balances[from] < value ) { | |
throw; | |
} | |
// if you don't have approval, throw | |
if( _approvals[from][msg.sender] < value ) { | |
throw; | |
} | |
if( !safeToAdd(_balances[to], value) ) { | |
throw; | |
} | |
// transfer and return true | |
_approvals[from][msg.sender] -= value; | |
_balances[from] -= value; | |
_balances[to] += value; | |
Transfer( from, to, value ); | |
return true; | |
} | |
function approve(address spender, uint value) returns (bool ok) { | |
// TODO: should increase instead | |
_approvals[msg.sender][spender] = value; | |
Approval( msg.sender, spender, value ); | |
return true; | |
} | |
function allowance(address owner, address spender) constant returns (uint _allowance) { | |
return _approvals[owner][spender]; | |
} | |
function safeToAdd(uint a, uint b) internal returns (bool) { | |
return (a + b >= a); | |
} | |
} |
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