File Filter

[shyla]

A file filter reads an input file, transforms it in some way, and
writes the results to an output file. Write an abstract file filter
class that defines a pure virtual function for transforming a character.
Create one subclass of your file filter class that performs encryption,
another that transforms a file to all uppercase, and another that
creates an unchanged copy of the original file. The class should have
a member function

i am trying to arrange my code and it gives me so many errors

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

void printFile(fstream &); // Prototype

int main( )
{
    // Explain the program
    cout << "This program creates an uppercase version of a file of text." << endl;
    cout << "Enter name of input file (input-file.txt): ";
    string inFileName;
    cin >> inFileName;
    fstream inputFile(inFileName.data(), ios::in);
    if (!inputFile)
    {
        cout << "The file " << inFileName << " cannot be opened." << endl;
        exit(1);
    }

    // Echo the input file
    cout << "\nOriginal file: " << endl << endl;

    printFile(inputFile);
    cout << endl << endl;

    cout << "Enter name of 3 output files (upper.txt encrypt.txt noop.txt): ";
    cout << endl;

    string upperFileName;
    cin >> upperFileName;
    fstream upperFile(upperFileName.data(), ios::out);
    if (! upperFile)
    {
        cout << "The file " << upperFileName << " cannot be opened." << endl;
        exit(1);
    }

    string encryptFileName;
    cin >> encryptFileName;
    fstream encryptFile(encryptFileName.data(), ios::out);
    if (! encryptFile)
    {
        cout << "The file " << encryptFileName << " cannot be opened." << endl;
        exit(1);
    }

    string noopFileName;
    cin >> noopFileName;
    fstream noopFile(noopFileName.data(), ios::out);
    if (! noopFile)
    {
        cout << "The file " << noopFileName << " cannot be opened." << endl;
        exit(1);
    }

    cout << "Enter an integer offset for the encryption filter: ";
    int encryptOffset = 0;
    cin >> encryptOffset;
    
    // For each filter, open the file, run it through the Filter object,
    // the print the results
    UpperCaseFilter upperFilter;
    upperFilter.doFilter(inputFile, upperFile);
    upperFile.close();

    // Re-open for reading
    upperFile.open(upperFileName.data(), ios::in);
    cout << endl << "Uppercase-filtered file: " << endl << endl;
    printFile(upperFile);
    upperFile.close();

    EncryptionFilter encryptFilter(encryptOffset);
    inputFile.clear();
    inputFile.seekg(0, ios::beg);
    encryptFilter.doFilter(inputFile, encryptFile);
    encryptFile.close();
    encryptFile.open(encryptFileName.data(), ios::in);
    cout << endl << "Encrypted file: " << endl << endl;
    printFile(encryptFile);
    encryptFile.close();

    NoOpFilter noopFilter;
    inputFile.clear();
    inputFile.seekg(0, ios::beg);
    noopFilter.doFilter(inputFile, noopFile);
    noopFile.close();
    noopFile.open(noopFileName.data(), ios::in);
    cout << endl << endl << "Unmodified (no-op filtered) file: " 
         << endl << endl;
    printFile(noopFile);
    noopFile.close();

    inputFile.close();

	system("pause");
    return 0;
}    

// *******************
//    printFile      *
// Print file        *
// *******************
void printFile(fstream &file)
{
   // Start at beginning of file
   file.clear(); 
   file.seekg(0, ios::beg);

   // Print the file contents
   char ch = file.get();
   while (ch != EOF)
   {
      // If the character is "non-printable", write its integer value instead.
      // (This is primarily needed for the encryption case.)
      if ((ch != '\n') && (ch != '\r') && ((ch < ' ') || (ch > 126)))
      {
          cout << '\\' << oct << setw(3) << fixed << setfill('0') 
               << static_cast<int>(ch) << dec;
      }
      else
          cout << ch;
      ch = file.get();
   }
   
   // Go back to beginning of file for further processing
   file.clear();
   file.seekg(0, ios::beg);
}

[jonsca]

Where is the code for UpperCaseFilter and EncryptionFilter?

[shyla]

Where is the code for UpperCaseFilter and EncryptionFilter?

You mean to insert prototype ?

[griswolf]

Write an abstract file filter class ... Create one subclass of your file filter class that performs encryption,
another that transforms a file to all uppercase, and another that creates an unchanged copy of the original file.

I don't see this (interface/abstract) class anywhere in your code

It seems to me that your file should look like:

class AbstractFilter {
  /** 
  * filter open inputFile into open outputFile, returning number of bytes written
  */
  int doFilter(inputFile,outputFile) = 0;
}
class IdentFilter : public AbstractFilter {
  /** copy byte for byte */
  // ...
}
class UpperCaseFilter : public AbstractFilter {
 /** change any char to its uppercase equivalent */
 // ...
}
class EncryptFilter : public AbstractFilter {
  /** encrypt the input file using (whatever you like) */
  // ...
}
int main(int argc, char** argv) {
  // user enters what to do, what files to do it to
  // then we instantiate the appropriate Filter class
  // and use it
  // and report that it was used
}

[ravenous]

I think you need:

class AbstractFilter{
    public:
        /* Need to have at least one pure virtual function to make an abstract class */
        virtual int doFilter( const std::ifstream& inFileStream, const std::ofstream& outFileStream ) = 0; 
};

[shyla]

Can you show me how do i need to arrange it with my code i kinda lost here

[jonsca]

You mean to insert prototype ?

I mean that you try to instantiate both classes, but they have not been written. That will give you an error or two. As others have mentioned, you haven't defined the abstract class that both of those will inherit from, either.

Can you show me how do i need to arrange it with my code

You probably want to put your class declaration for each (the base class and the two child classes) each in its own header file. It's not absolutely necessary, but it will keep things organized and neat. Then, you can put the implementation for each of the child classes in its own .cpp file.

Look for some examples of separating out the class files in your text or online. You're most of the way there, now you have to fill in the gaps.

[shyla]

Can you show me how do i need to arrange it with my code i kinda lost here

I don't see this (interface/abstract) class anywhere in your code

It seems to me that your file should look like:

class AbstractFilter {
  /** 
  * filter open inputFile into open outputFile, returning number of bytes written
  */
  int doFilter(inputFile,outputFile) = 0;
}
class IdentFilter : public AbstractFilter {
  /** copy byte for byte */
  // ...
}
class UpperCaseFilter : public AbstractFilter {
 /** change any char to its uppercase equivalent */
 // ...
}
class EncryptFilter : public AbstractFilter {
  /** encrypt the input file using (whatever you like) */
  // ...
}
int main(int argc, char** argv) {
  // user enters what to do, what files to do it to
  // then we instantiate the appropriate Filter class
  // and use it
  // and report that it was used
}