Thread: "Stray Character" when running a simple encryption program.

I wrote this simple program for my little cousin who wanted to see something useful done with a computer.
The bug it has is not much problem when 'encrypting' (sort of) text files.
The problem it has is that every time I encrypt a file and decrypt it, an extra character is introduced in the last line.Not a single of the individual functions (apparently) show this behaviour when tested individually .

I'm pasting the whole code for convenience.
[Note that you'd have to apply a c_str() to strings when used with the fstream open functions , if your compiler does not support c++0x/11 features. If it does, remember to tell it to explicitly do so...by something like gcc's -std=c++0x flag]

Code:

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


void encryption(string& data,string passkey);
void decryption(string& data,string passkey);
string get_file_input(string filename);
void output_to_file(const string& data, string filename); 
bool quit_condition();
void get_input(string&,string&,string&,string&);


int main(int argc,char** argv)
{ 
    string in_file_name,out_file_name,data,passkey;
    string enc_or_dec;
    bool input_ready;

    if(argc==1)input_ready=false;
    else
    {
    in_file_name = string(argv[1]);
    out_file_name = string(argv[2]);
    passkey = string(argv[3]);
    enc_or_dec = string(argv[4]);
    input_ready = true;
    }

    while(true)
    {
    if(input_ready); 
    else
        get_input(in_file_name,out_file_name,passkey,enc_or_dec);
    
    data = get_file_input(in_file_name);
    
    if(enc_or_dec[0]=='e'||enc_or_dec[0]=='E')
        encryption(data,passkey);
    else if(enc_or_dec[0]=='d'||enc_or_dec[0]=='D')
        decryption(data,passkey);
    else
    {
        cout<<"Enter ( E or D )! .*****."<<endl;
        if(!quit_condition())break;
        else continue;
    }
    output_to_file(data,out_file_name);
    
    if(input_ready)break;
    //^The Program doesn't allow the user to continue after supplying cmdline args
    if(!quit_condition())break;
    }
    return 0;
}
string get_file_input(string filename)
{
    ifstream is(filename);
    if(!is)
    {
    cout<<"File "<<filename<<" not found. Please try again.\n";
    return "";
    }
    else if(is.fail())
    {
    cout<<"Opening "<<filename<<" failed for some reason. Please try again.\n";
    return "";
    }
    string line,data("");
    do
    {
    getline(is,line);
    data = data+line+"\n";
    
    }while(!is.eof());
    return data;
}
void output_to_file(const string& data, string filename)
{
    ofstream os(filename);
    os<<data;
}
bool quit_condition()
{
    string q;
    cout<<"Quit?\n$ ";
    //q=getchar();
    cin>>q;
    if(q[0]=='y'||q[0]=='Y')
    return false;
    else return true;
}
void encryption(string& data,string passkey)
{
    int data_end(data.size()),passkey_bound(passkey.size());
    
    for(int counter=0;counter<data_end;counter++)
    {
    data[counter]+=passkey[counter%passkey_bound];
    }
}
void decryption(string& data,string passkey)
{
    int data_end(data.size()),passkey_bound(passkey.size());
    
    for(int counter=0;counter<data_end;counter++)
    {
    data[counter]-=passkey[counter%passkey_bound];
    }
}


void get_input(string& in_file_name,string& out_file_name,string& passkey,string& enc_or_dec)
{
    cout<<"Enter Input filename:\n$ ";
    cin>>in_file_name;
    cout<<"Enter Output filename:\n$ ";
    cin>>out_file_name;
    cout<<"Enter Passkey:\n$ ";
    cin>>passkey;
    cout<<"Enter ( E or D ) for enc/dec:\n$ ";
    cin>>enc_or_dec;
}

There is also a problem with an extra newline in the get_file_input function. I am also looking for a way to remove the last newline.

SourceForge.net: Feof - cpwiki

Code:

    do
    {
    getline(is,line);
    data = data+line+"\n";
    
    }while(!is.eof());

Try it with an empty file, you'll get a return string of a single \n

What you should have is
while ( getline(is,line) ) data = data+line+"\n";

What you should have is
while ( getline(is,line) ) data = data+line+"\n";

Ok..thanks