59_曾健生_第六课作业

Lesson-1/assignment/yours.sol

@@ -1 +1,66 @@
 /*作业请提交在这个目录下*/
+
+pragma solidity ^0.4.14;
+
+contract Payroll {
+    uint salary = 1 ether; //工资
+    address employee; //员工地址
+    address owner; //老板地址
+    uint lastPayday ; // 上次发薪水的时间
+
+    uint constant payDuration = 10 seconds;// 发薪水的时间间隔
+
+    //设置老板地址
+    function Payroll() public {
+        owner = msg.sender;
+    }
+
+
+    function updateEmployeeAddressSalary(address e, uint s){
+        require(msg.sender == owner);
+        require(s>0);
+
+        //修改前先结余
+        if(employee != 0x0 ){
+            uint shouldPay = salary*(now-lastPayday)/payDuration;
+            employee.transfer(shouldPay);
+        }
+
+        employee = e;
+        salary = s * 1 ether;
+        lastPayday = now;
+
+    }
+
+
+
+
+    //给智能合约打钱
+    function addFund() payable returns (uint) {
+        return this.balance;
+    }
+
+    //计算智能合约的钱能支付薪水多少次
+    function calculateRunway() returns (uint) {
+        return this.balance/salary;
+    }
+
+    //智能合约的钱是否足够支付薪水
+    function hasEnoughFund() returns (bool) {
+        return calculateRunway() > 0;
+    }
+
+    //获得薪水
+    function getPaid() {
+        require(msg.sender == employee);
+
+       uint nextPayday = lastPayday + payDuration;
+
+       assert(nextPayday<now);
+
+       lastPayday = nextPayday;
+
+       employee.transfer(salary);
+
+    }
+}

Lesson-2/assignment/README.md

@@ -8,3 +8,32 @@
 - 如何优化calculateRunway这个函数来减少gas的消耗？
 提交：智能合约代码，gas变化的记录，calculateRunway函数的优化
 
+### 回答：
+加入员工时，calculateRunway这个函数gas变化如下：
+
+ transaction cost,  execution cost 
+
+ 22966 1694
+
+ 23747 2475
+
+ 23528 3256
+
+ 25309 4037
+
+ 26090 4818
+
+ 26871 5599
+
+ 27652 6380
+
+ 28433 7161
+
+ 29214 7942
+
+ 29995 8723
+
+
+ 可以看到，在calculateRunway函数中，因为employees数组的长度不断增大，遍历这个数组所需要的gas也不断增大，所以需要把计算salary放在别的地方。
+
+ 优化后的程序写在answer.sol

Lesson-2/assignment/answer.sol

@@ -0,0 +1,119 @@
+/*
+加入员工时，calculateRunway这个函数gas变化如下：
+
+transaction cost, execution cost
+
+22966 1694
+
+23747 2475
+
+23528 3256
+
+25309 4037
+
+26090 4818
+
+26871 5599
+
+27652 6380
+
+28433 7161
+
+29214 7942
+
+29995 8723
+
+可以看到，在calculateRunway函数中，因为employees数组的长度不断增大，遍历这个数组所需要的gas也不断增大，所以需要把计算salary放在别的地方。
+
+*/
+
+pragma solidity ^0.4.14;
+
+contract Payroll {
+    struct Employee {
+        address id;
+        uint salary;
+        uint lastPayday;
+    }
+
+    uint constant payDuration = 10 seconds;
+
+    address owner;
+    Employee[] employees;
+    uint totalSalary =0;
+
+    function Payroll() {
+        owner = msg.sender;
+    }
+
+
+    function _partialPaid(Employee employee) private {
+        uint payment =  employee.salary * (now-employee.lastPayday)/payDuration;
+        employee.id.transfer(payment);
+    }
+
+    function _findEmployee(address employeeId) private returns (Employee, uint) {
+        for (uint i = 0; i < employees.length; i++) {
+            if( employeeId == employees[i].id ){
+                return (employees[i],i);
+            }
+        }
+    }
+
+    function addEmployee(address employeeId, uint salary) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id == 0x0);
+        totalSalary += salary* 1 ether;
+        employees.push(Employee(employeeId, salary* 1 ether, now));
+
+    }
+
+    function removeEmployee(address employeeId) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+        totalSalary -= employee.salary* 1 ether;
+        _partialPaid(employee);
+        delete employees[index];
+        employees[index] = employees[employees.length-1];
+        employees.length -=1;
+
+    }
+
+    function updateEmployee(address employeeId, uint salary) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+        totalSalary -= employee.salary* 1 ether;
+        _partialPaid(employee);
+        totalSalary += salary * 1 ether;
+        employee.lastPayday = now;
+        employee.salary = salary;
+    }
+
+    function addFund() payable returns (uint) {
+        return this.balance;
+    }
+
+    function calculateRunway() returns (uint) {
+        return this.balance / totalSalary;
+    }
+
+    function hasEnoughFund() returns (bool) {
+         return calculateRunway()>0;
+    }
+
+    function getPaid() {
+
+       var (employee,index) = _findEmployee(msg.sender);
+       require(employee.id == msg.sender);
+
+       uint nextPayday = employee.lastPayday+payDuration;
+       require(nextPayday<now);
+
+       employee.lastPayday = nextPayday;
+       employee.id.transfer(employee.salary);
+
+    }
+}

Lesson-2/assignment/yours.sol

@@ -1 +1,90 @@
 /*作业请提交在这个目录下*/
+
+pragma solidity ^0.4.14;
+
+contract Payroll {
+    struct Employee {
+        address id;
+        uint salary;
+        uint lastPayday;
+    }
+
+    uint constant payDuration = 10 seconds;
+
+    address owner;
+    Employee[] employees;
+
+    function Payroll() {
+        owner = msg.sender;
+    }
+
+
+    function _partialPaid(Employee employee) private {
+        uint payment =  employee.salary * (now-employee.lastPayday)/payDuration;
+        employee.id.transfer(payment);
+    }
+
+    function _findEmployee(address employeeId) private returns (Employee, uint) {
+        for (uint i = 0; i < employees.length; i++) {
+            if( employeeId == employees[i].id ){
+                return (employees[i],i);
+            }
+        }
+    }
+
+    function addEmployee(address employeeId, uint salary) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id == 0x0);
+        employees.push(Employee(employeeId, salary* 1 ether, now));
+    }
+
+    function removeEmployee(address employeeId) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+        _partialPaid(employee);
+        delete employees[index];
+        employees[index] = employees[employees.length-1];
+        employees.length -=1;
+
+    }
+
+    function updateEmployee(address employeeId, uint salary) {
+        require(owner == msg.sender);
+        var (employee,index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+        _partialPaid(employee);
+        employee.lastPayday = now;
+        employee.salary = salary;
+    }
+
+    function addFund() payable returns (uint) {
+        return this.balance;
+    }
+
+    function calculateRunway() returns (uint) {
+        uint totalSalary = 0;
+      for (uint i = 0; i < employees.length; i++) {
+            totalSalary += employees[i].salary;
+        }
+        return this.balance / totalSalary;
+    }
+
+    function hasEnoughFund() returns (bool) {
+         return calculateRunway()>0;
+    }
+
+    function getPaid() {
+
+       var (employee,index) = _findEmployee(msg.sender);
+       require(employee.id == msg.sender);
+
+       uint nextPayday = employee.lastPayday+payDuration;
+       require(nextPayday<now);
+
+       employee.lastPayday = nextPayday;
+       employee.id.transfer(employee.salary);
+
+    }
+}

Lesson-3/assignment/Ownable.sol

@@ -0,0 +1,23 @@
+pragma solidity ^0.4.14;
+
+contract Ownable {
+  address public owner;
+
+  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
+
+  function Ownable() public {
+    owner = msg.sender;
+  }
+
+  modifier onlyOwner() {
+    require(msg.sender == owner);
+    _;
+  }
+
+  function transferOwnership(address newOwner) public onlyOwner {
+    require(newOwner != address(0));
+    OwnershipTransferred(owner, newOwner);
+    owner = newOwner;
+  }
+
+}

Lesson-3/assignment/SafeMath.sol

@@ -0,0 +1,48 @@
+pragma solidity ^0.4.14;
+
+
+/**
+ * @title SafeMath
+ * @dev Math operations with safety checks that throw on error
+ */
+library SafeMath {
+
+  /**
+  * @dev Multiplies two numbers, throws on overflow.
+  */
+  function mul(uint256 a, uint256 b) internal pure returns (uint256) {
+    if (a == 0) {
+      return 0;
+    }
+    uint256 c = a * b;
+    assert(c / a == b);
+    return c;
+  }
+
+  /**
+  * @dev Integer division of two numbers, truncating the quotient.
+  */
+  function div(uint256 a, uint256 b) internal pure returns (uint256) {
+    // assert(b > 0); // Solidity automatically throws when dividing by 0
+    uint256 c = a / b;
+    // assert(a == b * c + a % b); // There is no case in which this doesn't hold
+    return c;
+  }
+
+  /**
+  * @dev Substracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
+  */
+  function sub(uint256 a, uint256 b) internal pure returns (uint256) {
+    assert(b <= a);
+    return a - b;
+  }
+
+  /**
+  * @dev Adds two numbers, throws on overflow.
+  */
+  function add(uint256 a, uint256 b) internal pure returns (uint256) {
+    uint256 c = a + b;
+    assert(c >= a);
+    return c;
+  }
+}