Thread: [Help Me]Very Simply Encrypt/Decrypt

ShiroAzure,

In addition to Mozza's correction, it may be desirable to tell the user that the choice three will cause the program to exit. Otherwise it appears that you presentation layer is done for the given design.

What sorts of ideas do you have for the activities associated with getting the key? That seems like a good place to start. I might consider using a separate function to extract the key from your 'Number.dat' file, because it is used by both the Encrypt and Decrypt functions....

Perhaps, because of the algorithm purposed by the assignment, one could use the same function (e.g. Transform) that accepts the key and applies it to the Unencrypted.txt/Encrypted.txt file depending on the menu choice made by the user.... Somgetething like:

Code:

void Transform( fstream &in, fstream &out, int key );

I looked on the wikipedia for the keyword fstream, and followed the external reference to cplusplus.com: fstream - C++ Reference. Check out the constructor link....

Best Regards,

Im breaking this down trying to get it 1 piece at a time.
Right now im trying to get the reading in and math functions down in this code

Code:

#include <iostream>
#include <fstream>

using namespace std;

int main(void)
{
  ifstream fReader("test.txt");

   int i;
   char str[255];


   string line;
   string previousLine;
  while(!fReader.eof())
  {
      if(line.length() > 0)
         previousLine = line;
      getline(fReader,line);
      cout << line << endl;

  }

  fReader.close();


   for( i = 0; i < previousLine.length(); i++)
   {
      cout << "previousLine[" << i << "] = " << previousLine[i] << endl;
   }

   for(i = 0; i < previousLine.length(); i++)
   {
      cout << previousLine[i] << " + 2 = " << char(previousLine[i]+2) <<
endl;
   }


   return 0;
}

this is just me trying to test it but for some reason its not reading both lines of test.txt, in test.txt i have written
THIS IS DUMB
AND OVERLY DIFFICULT

but when i run through this the only output i get it

THIS IS DUMB
AND OVERLY DIFFICULT


previousLine[0] = A
previousLine[1] = N
previousLine[2] = D
previousLine[3] =
previousLine[4] = O
previousLine[5] = V
previousLine[6] = E
previousLine[7] = R
previousLine[8] = L
previousLine[9] = Y
previousLine[10] =
previousLine[11] = D
previousLine[12] = I
previousLine[13] = F
previousLine[14] = F
previousLine[15] = I
previousLine[16] = C
previousLine[17] = U
previousLine[18] = L
previousLine[19] = T
A + 2 = C
N + 2 = P
D + 2 = F
+ 2 = "
O + 2 = Q
V + 2 = X
E + 2 = G
R + 2 = T
L + 2 = N
Y + 2 = [
+ 2 = "
D + 2 = F
I + 2 = K
F + 2 = H
F + 2 = H
I + 2 = K
C + 2 = E
U + 2 = W
L + 2 = N
T + 2 = V




so its only displaying the last line and converting it, how do i fix it so it reads out and prints out both?

Code:

   string line;
   string previousLine;
  while(fReader.good())  //tried (!fReader.eof()) as well
  {
      if(line.length() > 0)
         previousLine = line;
      getline(fReader,line);
      cout << line << endl;

   for( i = 0; i < previousLine.length(); i++)
   {
      cout << "previousLine[" << i << "] = " << previousLine[i] << endl;
   }

   for(i = 0; i < previousLine.length(); i++)
   {
      cout << previousLine[i] << " + 2 = " << char(previousLine[i]+2) <<
endl;
   }


  }

Like this?
Mozza thanks for putting up with me lol your being a huge help! Okay so now the problem im running into is that its running through and outputting the last line twice

Code:

THIS IS DUMB
AND OVERLY DIFFICULT
previousLine[0] = T
previousLine[1] = H
previousLine[2] = I
previousLine[3] = S
previousLine[4] =
previousLine[5] = I
previousLine[6] = S
previousLine[7] =
previousLine[8] = D
previousLine[9] = U
previousLine[10] = M
previousLine[11] = B
T + 2 = V
H + 2 = J
I + 2 = K
S + 2 = U
  + 2 = "
I + 2 = K
S + 2 = U
  + 2 = "
D + 2 = F
U + 2 = W
M + 2 = O
B + 2 = D

previousLine[0] = A
previousLine[1] = N
previousLine[2] = D
previousLine[3] =
previousLine[4] = O
previousLine[5] = V
previousLine[6] = E
previousLine[7] = R
previousLine[8] = L
previousLine[9] = Y
previousLine[10] =
previousLine[11] = D
previousLine[12] = I
previousLine[13] = F
previousLine[14] = F
previousLine[15] = I
previousLine[16] = C
previousLine[17] = U
previousLine[18] = L
previousLine[19] = T
A + 2 = C
N + 2 = P
D + 2 = F
  + 2 = "
O + 2 = Q
V + 2 = X
E + 2 = G
R + 2 = T
L + 2 = N
Y + 2 = [
  + 2 = "
D + 2 = F
I + 2 = K
F + 2 = H
F + 2 = H
I + 2 = K
C + 2 = E
U + 2 = W
L + 2 = N
T + 2 = V

previousLine[0] = A
previousLine[1] = N
previousLine[2] = D
previousLine[3] =
previousLine[4] = O
previousLine[5] = V
previousLine[6] = E
previousLine[7] = R
previousLine[8] = L
previousLine[9] = Y
previousLine[10] =
previousLine[11] = D
previousLine[12] = I
previousLine[13] = F
previousLine[14] = F
previousLine[15] = I
previousLine[16] = C
previousLine[17] = U
previousLine[18] = L
previousLine[19] = T
A + 2 = C
N + 2 = P
D + 2 = F
  + 2 = "
O + 2 = Q
V + 2 = X
E + 2 = G
R + 2 = T
L + 2 = N
Y + 2 = [
  + 2 = "
D + 2 = F
I + 2 = K
F + 2 = H
F + 2 = H
I + 2 = K
C + 2 = E
U + 2 = W
L + 2 = N
T + 2 = V

Thats what my output is, ive been trying to tweak it some but i just cant make it work.

ShiroAzure,

Your test on fReader.good(), on line 3, returns true after the stream has reached the end of the file. It isn't necessarily an error to have reached the end of file, but it is considered an error to attempt to read past it. Since your assignment isn't concerned with paging or memory contention, something like this should be effective:

Code:

...
   ifstream fReader("test.txt");

   if( !fReader.good() )
   {
      cout << "Error reading test.txt...exiting." << endl;

      return 1;
   }

   while( !fReader.eof() )
   {
      getline( fReader,currentline );
      lines.push_back( currentline );
   }

   fReader.close();
...

fReader.good() is more like a sanity check, e.g. does the file exist, can it be opened for reading, etc.... Then, the loop which loads the lines of the file into a list is controlled by whether or not the fReader has encountered an EOF during it's operations. After the file's entries, lines in this case, are loading into memory where they may be manipulated, the file is closed and processing continues.

After a walk through, it looks like the code you had would initially read the first line, but not initialize the previousLine variable, so the loops that print would not execute. Then the second time through the loop the line variable is non-empty, so previousLine is initialized, and the line variable is overwritten. At this point fReader encounters the EOF, but has not been asked to read past it so fReader is still good. The loops which print then execute, because previousLine is non-empty. (<== first line of file is coded/decoded) Finally, the outer loop's condition tests true again, because the file is still in a "good" state, line is non-empty so previousLine is overwritten, and the fReader is asked to read another line, but fails. The loops which print again execute. (<== second line of file is coded/decoded) The outer loop's condition fails because the file is no longer good, and execution continues after the loop body given.

I can't say why it is printing twice for you from the code you've given. Maybe one-too-many copy/pastes? I look forward to seeing your next try....

Best Regards,