pragma solidity ^0.4.5;
/*
GIVS是基于区块链去中心化、保护用户隐私的特性而搭建的全球智能视频服务链，通过与智能设备和服务的结合，将区块链这项技术有机的关联实体行业并赋能，真正的实现区块链应用落地和广泛的使用前景。
*/
contract Token{
    
    uint256 public totalSupply;

    function balanceOf(address _owner) constant returns (uint256 balance);

    function transfer(address _to, uint256 _value) returns (bool success);

    function transferFrom(address _from, address _to, uint256 _value) returns   
    (bool success);

    function approve(address _spender, uint256 _value) returns (bool success);

    function allowance(address _owner, address _spender) constant returns 
    (uint256 remaining);

    event Transfer(address indexed _from, address indexed _to, uint256 _value);

    event Approval(address indexed _owner, address indexed _spender, uint256 
    _value);
}

contract StandardToken is Token {
    function transfer(address _to, uint256 _value) returns (bool success) {
 
        require(balances[msg.sender] >= _value);
        balances[msg.sender] -= _value;
        balances[_to] += _value;
        Transfer(msg.sender, _to, _value);
        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[_from] -= _value;
        allowed[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value);
        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];
    }
    mapping (address => uint256) balances;
    mapping (address => mapping (address => uint256)) allowed;
}

contract HumanStandardToken is StandardToken { 

    string public name;             
    uint8 public decimals;              
    string public symbol;         
    string public version = 'H0.1'; 

    function HumanStandardToken(uint256 _initialAmount, string _tokenName, uint8 _decimalUnits, string _tokenSymbol) {
        balances[msg.sender] = _initialAmount; 
        totalSupply = _initialAmount; 
        name = _tokenName;   
        decimals = _decimalUnits;  
        symbol = _tokenSymbol;  
    }

    
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success) {
        allowed[msg.sender][_spender] = _value;
        Approval(msg.sender, _spender, _value);
        require(_spender.call(bytes4(bytes32(sha3("receiveApproval(address,uint256,address,bytes)"))), msg.sender, _value, this, _extraData));
        return true;
    }

}