以太坊智能合约开发 Solidity学习

pragma solidity ^0.4.8;

contract Token{

    // token总量，默认会为public变量生成一个getter函数接口，名称为totalSupply().

    uint256 public totalSupply;

    /// 获取账户_owner拥有token的数量

    function balanceOf(address _owner) constant returns (uint256 balance);

    //从消息发送者账户中往_to账户转数量为_value的token

    function transfer(address _to, uint256 _value) returns (bool success);

    //从账户_from中往账户_to转数量为_value的token，与approve方法配合使用

    function transferFrom(address _from, address _to, uint256 _value) returns

    (bool success);

    //消息发送账户设置账户_spender能从发送账户中转出数量为_value的token

    function approve(address _spender, uint256 _value) returns (bool success);

    //获取账户_spender可以从账户_owner中转出token的数量

    function allowance(address _owner, address _spender) constant returns

    (uint256 remaining);

    //发生转账时必须要触发的事件

    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    //当函数approve(address _spender, uint256 _value)成功执行时必须触发的事件

    event Approval(address indexed _owner, address indexed _spender, uint256

    _value);

}

contract StandardToken is Token {

    function transfer(address _to, uint256 _value) returns (bool success) {

        //默认totalSupply 不会超过最大值 (2^256 - 1).

        //如果随着时间的推移将会有新的token生成，则可以用下面这句避免溢出的异常

        //require(balances[msg.sender] >= _value && balances[_to] + _value > balances[_to]);

        require(balances[msg.sender] >= _value);

        balances[msg.sender] -= _value;//从消息发送者账户中减去token数量_value

        balances[_to] += _value;//往接收账户增加token数量_value

        Transfer(msg.sender, _to, _value);//触发转币交易事件

        return true;

    }

    function transferFrom(address _from, address _to, uint256 _value) returns

    (bool success) {

        //require(balances[_from] >= _value && allowed[_from][msg.sender] >=

        // _value && balances[_to] + _value > balances[_to]);

        require(balances[_from] >= _value && allowed[_from][msg.sender] >= _value);

        balances[_to] += _value;//接收账户增加token数量_value

        balances[_from] -= _value; //支出账户_from减去token数量_value

        allowed[_from][msg.sender] -= _value;//消息发送者可以从账户_from中转出的数量减少_value

        Transfer(_from, _to, _value);//触发转币交易事件

        return true;

    }

    function balanceOf(address _owner) constant returns (uint256 balance) {

        return balances[_owner];

    }

    function approve(address _spender, uint256 _value) returns (bool success)

    {

        allowed[msg.sender][_spender] = _value;

        Approval(msg.sender, _spender, _value);

        return true;

    }

    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {

        return allowed[_owner][_spender];//允许_spender从_owner中转出的token数

    }

    mapping (address => uint256) balances;

    mapping (address => mapping (address => uint256)) allowed;

}

contract HumanStandardToken is StandardToken {

    /* Public variables of the token */

    string public name;                   //名称: eg Simon Bucks

    uint8 public decimals;               //最多的小数位数，How many decimals to show. ie. There could 1000 base units with 3 decimals. Meaning 0.980 SBX = 980 base units. It's like comparing 1 wei to 1 ether.

    string public symbol;               //token简称: eg SBX

    string public version = 'H0.1';    //版本

     function HumanStandardToken() {

        balances[msg.sender] = 10000000000; // 初始token数量给予消息发送者

        totalSupply = 10000000000;         // 设置初始总量

        name = "bawei";                   // token名称

        decimals = 8;           // 小数位数

        symbol = "BW";             // token简称

    }

    /* Approves and then calls the receiving contract */

    function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success) {

        allowed[msg.sender][_spender] = _value;

        Approval(msg.sender, _spender, _value);

        //call the receiveApproval function on the contract you want to be notified. This crafts the function signature manually so one doesn't have to include a contract in here just for this.

        //receiveApproval(address _from, uint256 _value, address _tokenContract, bytes _extraData)

        //it is assumed that when does this that the call *should* succeed, otherwise one would use vanilla approve instead.

        require(_spender.call(bytes4(bytes32(sha3("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData));

        return true;

    }

}