C++二进制文件读写实例教程

struct Student {
    char name[20];
    int age;
    float score;
// 构造函数方便初始化
Student(const char* n, int a, float s) {
    strncpy(name, n, 19);
    name[19] = '\0';
    age = a;
    score = s;
}
Student() = default; // 默认构造函数用于读取
};

void writeBinary() {
    std::ofstream file("students.dat", std::ios::binary);
    if (!file) {
        std::cerr << "无法打开文件进行写入！\n";
        return;
    }
Student s1("Alice", 20, 88.5f);
Student s2("Bob", 21, 92.0f);
Student s3("Charlie", 19, 76.5f);

// 一次性写入多个对象
Student students[] = {s1, s2, s3};
file.write(reinterpret_cast(students), sizeof(students));

file.close();
std::cout << "数据已写入 students.dat\n";
}

void readBinary() {
    std::ifstream file("students.dat", std::ios::binary);
    if (!file) {
        std::cerr << "无法打开文件进行读取！\n";
        return;
    }
Student students[3];
file.read(reinterpret_cast(students), sizeof(students));

// 检查是否成功读取全部数据
if (file.gcount() != sizeof(students)) {
    std::cerr << "读取数据不完整！\n";
} else {
    for (int i = 0; i < 3; ++i) {
        std::cout << "姓名: " << students[i].name
                 << ", 年龄: " << students[i].age
                 << ", 成绩: " << students[i].score << "\n";
    }
}

file.close();
}

int main() {
    writeBinary();  // 先写入数据
    readBinary();   // 再读取验证
    return 0;
}