读写二进制文件

#include <cstdlib>
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

/*
 * 
 */
inline void eatline() {while(cin.get() != '\n') continue;}
struct planet{
    char name[20];
    double population;
    double g;
};

const char *file = "planets.dat";
int main(int argc, char** argv) {

    planet pl;
    cout<<fixed<<right;
    ifstream fin;
    fin.open(file,ios_base::in | ios_base::binary);
    if(fin.is_open())
    {
        cout<<"Here are the contents of "<<file<<" file: \n";
        while(fin.read((char*)&pl,sizeof(pl)))
        {
            cout<<setw(20)<<pl.name<<": "
                <<setprecision(0)<<setw(12)<<pl.population
                <<setprecision(2)<<setw(6)<<pl.g<<endl;
        }
        fin.close();
    }
    
    ofstream fout(file,ios_base::out | ios_base::app | ios_base::binary);
    if(!fout.is_open())
    {
        cerr<<"Can`t open "<<file<<" file for output; \n";
        exit(EXIT_FAILURE);
    }
    cout<<"Enter planet name (enter a blank to quit): \n";
    cin.get(pl.name,20);
    while(pl.name[0] != '\0')
    {
        eatline();
        cout<<"Enter planetary population: ";
        cin>>pl.population;
        cout<<"Enter planet`s acceleration of gravity: ";
        cin>>pl.g; 
        eatline();
        fout.write((char*)&pl,sizeof pl);
        cout<<"Enter planet name (enter a blank to quit): \n";
        cin.get(pl.name,20);
    }
    fout.close();
    
    fin.clear();
    fin.open(file,ios_base::in | ios_base::binary);
    if(fin.is_open())
    {
        cout<<"Here are the new contents of the "<<file<<" file: \n";
        while(fin.read((char*)&pl,sizeof pl))
        {
            cout<<setw(20)<<pl.name<<": "
                <<setprecision(0)<<setw(12)<<pl.population
                <<setprecision(2)<<setw(6)<<pl.g<<endl;
        }
        fin.close();
    }
    return 0;
}