Question

我创建了一个有两个字符串对象的类。此类在二进制模式中向/从文件中写入和读取两个字符串对象。所有这些都在头文件＆＃34; a_details.h＆＃34;中定义。

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

class AVENGERS{

public:
string codename;
string realname;
const size_t JUMP = 2*sizeof(string);
AVENGERS(string code=" ",string real=" "){codename=code;realname=real;}

void read(istream & is){
is.read((char*)&codename,sizeof(string));
is.read((char*)&realname,sizeof(string));
}

void write(ostream & os){
os.write((char*)&codename,sizeof(string));
os.write((char*)&realname,sizeof(string));
}

};
istream & operator >> (istream & is,AVENGERS & A)
{

    is>>A.codename>>A.realname;
   return is;

}

ostream & operator << (ostream & os,AVENGERS & A)
{

    os<<A.codename<<"-"<<A.realname;
   return os;

}

下面是文件＆＃34; a_write.cpp＆＃34;它以二进制模式打开文件并写入3个AVENGERS对象（因此，6个字符串）。

#include <iostream>
#include <fstream>
#include <string>
#include "a_details.h"
using namespace std;

int main(){
fstream ffile("avengers.bin", ios_base::binary | ios_base::in |ios_base::out);
if(ffile.is_open()){
AVENGERS("Iron Man","Tony Stark").write(ffile);
AVENGERS("Captain America","Steve Rogers").write(ffile);
AVENGERS("Hulk","Bruce Banner").write(ffile);

cout<<"writing done\n";

ffile.close();
}

}

之后，我检查了avengers.bin的大小是24个字节，以验证写操作是否正确完成。但是，当我创建另一个文件时＆＃34; a_read.cpp＆＃34;读入数据，它给了我错误。下面是代码。

#include <iostream>
#include <fstream>
#include <string>
#include "a_details.h"
using namespace std;

int main(){

fstream ffile("avengers.bin" , ios_base::binary | ios_base :: in |ios_base::out);

if(ffile.is_open()){
        cout<<"file is going to open"<<endl;
while(!ffile.eof())
    {
        cout<<"entered loop\n";
     AVENGERS TEMPO(" "," ");
      TEMPO.read(ffile);
cout<<"read data\n";
if(ffile.gcount()==0)break;

cout<<"this means file is not at end of file\n";
    }

    cout<<"this means file is at end of file\n";
ffile.close();


}
cout<<"reading done";

return 0;
}

之间的cout语句供我参考，因为我想查看问题所在。但我无法理解。程序循环1次，然后崩溃。有人能帮帮我吗？ This is the Error message

使用c ++中的字符串进行文件i / o的问题

0 个答案: