文件信息的删除

/*
    题目来源：<span style="color: #008000; text-decoration: underline;">https://bbs.bccn.net/thread-415375-1-1.html[/color]
    编程环境：Visual Studio 2012 C++
    2013.06.25
*/

#include <cstdio>
#include <cstdlib>
#include <vector>
#include <conio.h>
#include "Employee.h"

void Pause(void);
bool Init(void);

const char* file_name = "data.txt";

void main(void)
{
    // 构建原始数据
    Init();

    printf_s("文件中的原始数据\n");
    std::vector<Employee*> employees = Employee::Load_Data(file_name);
    Employee::List(employees);

    Pause();

    // 删除一条记录并储存到文件中
    employees[1]->Delete();
    Employee::Save_Data(file_name, employees, 0, employees.size());

    printf_s("\n\n删除后的数据\n");
    Employee::List(Employee::Load_Data(file_name), false);

    Pause();
}

void Pause(void)
{
    printf_s("\nPress any key to continue...");
    _getch();
}

// 生成原始数据文件
bool Init(void)
{
    Employee* employees[] = {
        new Employee(110, 1, "张三", 25, 1900),
        new Employee(111, 2, "李四", 28, 1700),
        new Employee(112, 3, "王五", 30, 1900)
    };
    FILE* file;
    errno_t error_code = fopen_s(&file, file_name, "wb");
    if (error_code != 0)
    {
        printf_s("File %s open error: %d\n", file_name, error_code);
        return false;
    }
    for (size_t index = 0; index < _countof(employees); ++index)
    {
        Employee::Write_Record(*employees[index], file);
    }
    fclose(file);
    return true;
}

#ifndef _EMPLOYEE
#define _EMPLOYEE

class Employee
{
private:

    bool _deleted;      // 删除标志
    int _id;            // 工号
    int _type;          // 职工类型
    char _name[20];     // 姓名
    int _age;           // 年龄
    int _pay;           // 工资

public:

    Employee();
    Employee(int id, int type, const char* name, int age, int pay);

    void Display(void);
    const char* const ToString(void);
    void Delete(void);
    void Recall(void);
    bool IsDeleted(void);

    static Employee* Read_Record(FILE* file);
    static void Write_Record(Employee& record, FILE* file);
    static std::vector<Employee*> Load_Data(const char* file_name);
    static bool Save_Data(const char* file_name, std::vector<Employee*> employees, int start, size_t count);
    static void List(std::vector<Employee*>& employees, bool show_deleted = true);
};

#endif

#include <cstdio>
#include <cstring>
#include <vector>
#include "Employee.h"

static const char* Employee_Type[] = {
    "教师",
    "临时教师",
    "主任"
};

Employee::Employee()
{
    _deleted = false;
    _id = 0;
    _type = 0;
    _name[0] = '\0';
    _age = 0;
    _pay = 0;
}

Employee::Employee(int id, int type, const char* name, int age, int pay)
{
    _deleted = false;
    _id = id;
    _type = type;
    strncpy_s(_name, name, sizeof(_name) - 1);
    _age = age;
    _pay = pay;
}

void Employee::Display(void)
{
    printf_s("工号: %03d\n", _id);
    printf_s("类型: %s\n", Employee_Type[_type - 1]);
    printf_s("姓名: %s\n", _name);
    printf_s("年龄: %d\n", _age);
    printf_s("工资: %d\n\n", _pay);
}

const char* const Employee::ToString(void)
{
    const size_t buffer_size = 100;
    char* buffer = new char[buffer_size];
    if (buffer != nullptr)
    {
        sprintf_s(buffer, buffer_size, "%c%03d %-10s %-20s %2d %6d", _deleted ? '*' : ' ', _id, Employee_Type[_type - 1], _name, _age, _pay);
    }
    return buffer;
}

void Employee::Delete(void)
{
    _deleted = true;
}

void Employee::Recall(void)
{
    _deleted = false;
}

bool Employee::IsDeleted(void)
{
    return _deleted;
}

Employee* Employee::Read_Record(FILE* file)
{
    Employee* e = new Employee;
    if ((e == nullptr) || fread(e, sizeof(Employee), 1, file) != 1)
    {
        e = nullptr;
    }
    return e;
}

void Employee::Write_Record(Employee& record, FILE* file)
{
    fwrite(&record, sizeof(Employee), 1, file);
}

std::vector<Employee*> Employee::Load_Data(const char* file_name)
{
    std::vector<Employee*> employees;
    FILE* file;
    errno_t error_code = fopen_s(&file, file_name, "rb");
    if (error_code == 0)
    {
        Employee* e;
        while (e = Employee::Read_Record(file))
        {
            employees.push_back(e);
        }
        fclose(file);
    }
    else
    {
        printf_s("File %s open error: %d\n", file_name, error_code);
    }
    return employees;
}

bool Employee::Save_Data(const char* file_name, std::vector<Employee*> employees, int start, size_t count)
{
    bool result(true);
    FILE* file;
    errno_t error_code = fopen_s(&file, file_name, "wb");
    if (error_code != 0)
    {
        printf_s("File %s create error: %d\n", file_name, error_code);
        result = false;
    }
    for (size_t index = start; index < start + count; ++index)
    {
        Employee::Write_Record(*employees[index], file);
    }
    fclose(file);
    return result;
}

void Employee::List(std::vector<Employee*>& employees, bool show_deleted)
{
    for (std::vector<Employee*>::const_iterator iterator = employees.cbegin(); iterator != employees.cend(); ++iterator)
    {
        if (!(*iterator)->IsDeleted() || show_deleted)
        {
            const char* const buffer = (*iterator)->ToString();
            printf_s("%s\n", buffer);
            delete buffer;
        }
    }
}