74_李想_第五次作业

Lesson2/assignment/gas_cost.md

@@ -0,0 +1,40 @@
+### calculateRunway cost
+
+- employee 1
+  + transaction cost    22966 gas
+  + execution cost     1694 gas
+- employee 2
+  + transaction cost     23747 gas
+  + execution cost     2475 gas
+- employee 3
+  + transaction cost    24528 gas
+  + execution cost     3256 gas
+- employee 4
+  + transaction cost    25309 gas
+  + execution cost     4037 gas
+- employee 5
+  + transaction cost    25309 gas
+  + execution cost     4037 gas
+- employee 6
+  + transaction cost    26090 gas
+  + execution cost     4818 gas
+- employee 7
+  + transaction cost    26871 gas
+  + execution cost     5599 gas
+- employee 8
+  + transaction cost    27652 gas
+  + execution cost     6380 gas
+- employee 9
+  + transaction cost    28433 gas
+  + execution cost     7161 gas
+- employee 10
+  + transaction cost    29214 gas
+  + execution cost     7942 gas
+
+### why
+
+calculateRunway每次都循环一次employees array来计算totalSalay, employee的人数越多消耗的gas越多。
+
+### 优化
+
+每次加入或者删除employee的时候直接更新totalSalary，就免去了calculaterunway中的遍历。

Lesson2/assignment/yours.sol

@@ -1 +1,94 @@
-/*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;
+    uint totalSalary;
+
+    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; i < employees.length; i++) {
+            if (employees[i].id == employeeId) {
+                return (employees[i], i);
+            }
+        }
+    }
+
+    function addEmployee(address employeeId, uint salary) {
+        require(msg.sender == owner);
+
+        var (employee, index) = _findEmployee(employeeId);
+
+        assert(employee.id == 0x0);
+
+        totalSalary += salary;
+        employees.push(Employee(employeeId, salary, now));
+    }
+
+    function removeEmployee(address employeeId) {
+        require(msg.sender == owner);
+        var (employee, index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+
+        _partialPaid(employee);
+        totalSalary -= employee.salary;
+        delete employees[index];
+        employees[index] = employees[employees.length-1];
+        employees.length -= 1;
+    }
+
+    function updateEmployee(address employeeId, uint salary) {
+        require(msg.sender == owner);
+        var (employee, index) = _findEmployee(employeeId);
+        assert(employee.id != 0x0);
+
+        _partialPaid(employees[index]);
+        totalSalary -= employee.salary;
+        totalSalary += salary;
+        employees[index].salary = salary;
+        employees[index].lastPayday = now;
+    }
+
+    function addFund() payable returns (uint) {
+        return this.balance;
+    }
+
+    function calculateRunway() returns (uint) {
+        assert(totalSalary != 0x0);
+        return this.balance / totalSalary;
+    }
+
+    function hasEnoughFund() returns (bool) {
+        if (totalSalary == 0x0) {
+            return true;
+        }
+        return calculateRunway() > 0;
+    }
+
+    function getPaid() {
+        var (employee, index) = _findEmployee(msg.sender);
+        assert(employee.id != 0x0);
+
+        uint nextPayday = employee.lastPayday + payDuration;
+        assert(nextPayday < now);
+
+        employee.lastPayday = nextPayday;
+        employee.id.transfer(employee.salary);
+    }
+}