Question

我收到此错误＆＃34; 0xC0000005： c ++ 程序中的访问冲突写入位置0xfeeefeee＆＃34; 。

我的代码是

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

class Employee
{
public: 
string name; 
int age;
int phone;
int salary;
};
int main()
{

Employee emp1;

ofstream f1;

f1.open("qwe.txt",ios::binary|ios::app);

for(int i=0;i<2;i++)

{
    cout<<"enter name:\t";
    cin>>emp1.name;
    cout<<"enter age:\t";
    cin>>emp1.age;
    cout<<"enter phone:\t";
    cin>>emp1.phone;
    cout<<"enter salary:\t";
    cin>>emp1.salary;
    cout<<"\n";
    f1.write((char *)(&emp1),sizeof(Employee));
}

f1.close();

Employee emp2;
ifstream f2;
f2.open("qwe.txt",ios::binary|ios::in);
while(f2)
{
    f2.read((char *)(&emp2),sizeof(Employee));
    if(f2.eof())
    {
        break;
    }

    else
    {
        cout<<"\n"<<emp2.name;
        cout<<"\n"<<emp2.age;
        cout<<"\n"<<emp2.phone;
        cout<<"\n"<<emp2.salary<<"\n";  
    }
}
f2.close();

cin.get();
return 0;
}

我认为问题出在while(f2)。但我不确定。这一行f2.read((char *)(&emp2),sizeof(Employee))可能会产生问题。但我需要这一行。

Answer 1

您无法以这种方式读取/编写具有复杂类型的结构，例如std::string。它们具有特定于实现的内部结构。直接覆盖它的记忆是一种可靠的射击方式。请改为使用>> / <<运营商：

f1 << emp1.name;
f1 << emp1.age;
//...
f2 >> emp2.name;
f2 >> emp2.age;

Answer 2

类的内部表示是实现定义的。此外，string成员可以直接或在另一个堆对象中保存数据，具体取决于字符数。

这就是为什么你需要对你的类的实例进行序列化的原因。序列化函数将采用类似ofstream的序列化目标，并写入数据的表示。反序列化函数将采用类似ifstream的序列化源，并向成员读取重新表示。

Answer 3

如果您需要代码中使用的低级API（读/写），请查看：

请注意，以下行可能会破坏您的数据，我对此进行了更改，以避免您之前的估价值。

f1.open("qwe.txt", ios::binary | ios::trunc);

完整代码：

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
using namespace std;

class Employee {
 public:
  string name;
  int age;
  int phone;
  int salary;
};
int main() {
  Employee emp1;

  ofstream f1;

  f1.open("qwe.txt", ios::binary | ios::trunc);

  for (int i = 0; i < 2; i++)

  {
    cout << "enter name:\t";
    cin >> emp1.name;
    cout << "enter age:\t";
    cin >> emp1.age;
    cout << "enter phone:\t";
    cin >> emp1.phone;
    cout << "enter salary:\t";
    cin >> emp1.salary;
    cout << "\n";

    size_t lenght = emp1.name.size();
    char lenghtval[sizeof(lenght)];
    std::memcpy(&lenghtval, &lenght, sizeof(lenght));
    f1.write(lenghtval, sizeof(lenght));
    const char *name = emp1.name.c_str();
    f1.write(name, static_cast<int>(lenght));
    int val = emp1.age;
    char towrite[sizeof(val)];
    std::memcpy(&towrite, &val, sizeof(val));
    f1.write(towrite, sizeof(val));
    val = emp1.phone;
    std::memcpy(&towrite, &val, sizeof(val));
    f1.write(towrite, sizeof(val));
    val = emp1.salary;
    std::memcpy(&towrite, &val, sizeof(val));
    f1.write(towrite, sizeof(val));
  }

  f1.close();

  Employee emp2;
  ifstream f2;
  f2.open("qwe.txt", ios::binary | ios::in);
  while (f2) {
    size_t lenght = 0;
    char lenghtval[sizeof(lenght)];
    f2.read(lenghtval, sizeof(lenght));
    std::memcpy(&lenght, lenghtval, sizeof(lenght));
    char name[lenght + 1];
    f2.read(name, static_cast<int>(lenght));
    name[lenght] = '\0';
    emp2.name = name;

    int val = 0;
    char toread[sizeof(val)];
    f2.read(toread, sizeof(val));
    std::memcpy(&val, toread, sizeof(val));
    emp2.age = val;
    f2.read(toread, sizeof(val));
    std::memcpy(&val, toread, sizeof(val));
    emp2.phone = val;
    f2.read(toread, sizeof(val));
    std::memcpy(&val, toread, sizeof(val));
    emp2.salary = val;

    if (f2.eof()) {
      break;
    }
    cout << "\n" << emp2.name << std::endl;
    cout << "\n" << emp2.age;
    cout << "\n" << emp2.phone;
    cout << "\n" << emp2.salary << "\n";
  }
  f2.close();

  cin.get();
  return 0;
}

C ++错误：0xC0000005：访问冲突写入位置0xfeeefeee

3 个答案: