c++ - fstream skips the first character

Question

I am trying to read first 121 bytes from a text file onto a structure.

Here is my code.

#include <fstream.h>
#include <iostream.h>
#include <conio.h>
#include <sys/stat.h>

int main()
{
    struct 
    {
        char map[121];
    } map_data;

    struct stat results;

    fstream myfile("input.txt", ios::in);

    myfile.read((char *)&map_data,121);

    if(!myfile)
    {
           cout<<"Unable to open the file";
    }
    if(!myfile.read((char *)&map_data,121))
    {
       cout<<"Second error occurred";
    }

    myfile.close();
    cout<<"\n Here are the read contents of size "<<sizeof(map_data)<<"\n";



    fstream outfile("output.txt", ios::out);
    for(int i=0;i<121;i++)
    {
        cout<<map_data.map[i]<<" ";
    }
    outfile.write((char *)&map_data,121);


    outfile.close();
    stat("input.txt",&results);
    cout<<"\n Size of input.txt "<<results.st_size;

    stat("output.txt",&results);
    cout<<"\n Size of output.txt "<<results.st_size;

    getch();

}

The problem is that the above code skips the first character of the file i.e the h of the hello. Its cout and the output.txt file both show this thing.

Can somebody guide me how to solve this?

Answer 1

I followed the guide courses.cs.vt.edu/cs2604/fall02/binio.html

The example shows two different ways to read a file notice a ... in between example.

It also says // Same effect as above

So just comment out either of the two read call.

    fstream myfile("input.txt", ios::in);

    //myfile.read((char *)&map_data,121);

    if(!myfile.read((char *)&map_data,121))
    {
       cout<<"Second error occurred";
    }

Answer 2

I'm semi surprised that only the first character is missing. It ought to be missing 121 chars.

fstream myfile("input.txt", ios::in);

// you read 121 bytes here...
myfile.read((char *)&map_data,121);

if (!myfile) {
    cout<<"Unable to open the file";
}

// and then do it again here, before you ever look at `map_data`.
if (!myfile.read((char *)&map_data,121)) {
    cout<<"Second error occurred";
}