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in and out stream

test1234 (24)
I am having to do a caesars cipher program and when I encrypt a file it works fine but the problem is when I decrypt.

Example
I have a file called "plain" that has ABCDE in it.
When I encrypt, i name the new file, "cipher" and use a key of 5. It stores FGHIJ in it. When I try to decrypt the "cipher" file, it just hangs. So I stop the program. If I create a file called "cipher" and put FGHIJ in it, and decrypt it with a key of 5, it works perfectly. I had everything working perfect then I went through to try and simplify the code and now this is happening. Please help!

closed account (48T7M4Gy)
Maybe showing us your code would be a good move?
test1234 (24)
clear
Last edited on
test1234 (24)
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#include <cstdlib>
#include <ctype.h>
#include <stdio.h>
#include <iostream>
#include <fstream>
using namespace std;

/* ============================================================================
Function :write my info
Parameters :none
Return :none void
Description :writes my info
============================================================================
*/
void outPut();
/* ============================================================================
Function :encrypt
Parameters :input and output
Return :none void
Description :encrypts plaintext
============================================================================
*/
void doEncrypt(char input[32], char output[32]);
/* ============================================================================
Function :decrypt
Parameters :none
Return :none void
Description :decrypts ciphertext
============================================================================
*/
void doDecrypt(char input[32], char output[32]);

ifstream in_stream;//global variables
ofstream out_stream;
char orig_symbol;
char new_symbol;

int main()
{
	char response;
	char input[32];
	char output[32];
	
	outPut();//calling function

	cout << "Would you like to ENCRYPT or DECRYPT (E or D)? ";//ask what they want to do
	cin >> response;
	
	while (response != 'e' && response != 'd' && response != 'D' && response != 'E')//if they put in wrong letter, keep prompting
	{
	cout << "Would you like to ENCRYPT or DECRYPT (E or D)? ";
	cin >> response; 
	}
	
	if(response == 'e' || response == 'E')//if they want to encrypt
	{
		cout << "Enter the name of your input file you want to encrypt: ";
		cin >> input;
		cout << "Enter the name of the output file to write the ciphertext: ";
		cin >> output;
		in_stream.open(input);//open stream
		out_stream.open(output);//open stream
		if(in_stream.fail())//if opening fails
        	{
                	cout << "Input file opening failed.\n";
                	exit(EXIT_FAILURE);
        	}
		doEncrypt(input, output);//calling function
		out_stream.close( );//close stream
        	in_stream.close( );//close stream
	}
	if(response == 'd' || response == 'D')//if they want to decrypt
        {
                cout << "Enter the name of your input file you want to decrypt: ";
                cin >> input;
		cout << "Enter the name of the output file to write the plaintext: ";
                cin >> output;
		in_stream.open(input);//open stream
                out_stream.open(output);//open stream
		if(in_stream.fail())//if opeining fails
        	{
                	cout << "Input file opening failed.\n";
                	exit(EXIT_FAILURE);
        	}
        	doDecrypt(input, output);//calling function
		out_stream.close( );//close stream
        	in_stream.close( );//close stream
        }
	return 0;
}
void doEncrypt(char input[32], char output[32])
{
	cout << "YOU WANT TO ENCRYPT" << endl;
	int shiftvalue;
	cout << "Enter the numerical key (i.e., an integer) used to encrypt: ";
	cin >> shiftvalue;
	in_stream.get(orig_symbol);//get character
	while(orig_symbol != '\n')//while the character is not on next line
        {
                if(isupper(orig_symbol)||islower(orig_symbol)||isdigit(orig_symbol))//if the character is uppercase,lowercase, or numeric
                {
                        if(isupper(orig_symbol))
                        {
                                new_symbol=((orig_symbol+shiftvalue - 65) % 26) + 65;//65 is the offset of ASCII
                        	out_stream.put(new_symbol);
			}
                        if(islower(orig_symbol))
                        {
                                new_symbol=((orig_symbol+shiftvalue - 97) % 26) + 97;//97 is the offset of ASCII
                        	out_stream.put(new_symbol);
			}
                        if(isdigit(orig_symbol))
                        {
                                new_symbol=((orig_symbol+shiftvalue - 48) % 10) + 48;//48 is the offset of ASCII
                  		out_stream.put(new_symbol);
			}
                }
		in_stream.get(orig_symbol);                
        }
}
void doDecrypt(char input[32], char output[32])
{
	cout << "YOU WANT TO DECRYPT" << endl;
	int shiftvalue = 0;
	int tempvalue;
	cout << "Enter the numerical key (i.e., an integer) used to decrypt: ";
	cin >> shiftvalue; 
	in_stream.get(orig_symbol);
	while(orig_symbol != '\n')//while the character is not on next line
        {
                if(isupper(orig_symbol)||islower(orig_symbol)||isdigit(orig_symbol))//if the character is uppercase,lowercase, or numeric
                {
                        if(isupper(orig_symbol))
                        {
				if(shiftvalue >= 26)
				{
					tempvalue = shiftvalue % 26;	
				}else
				{
					tempvalue = shiftvalue;
				}
                                new_symbol=((26 + orig_symbol-tempvalue - 65) % 26) + 65;//65 is the offset of ASCII
                                out_stream.put(new_symbol);
			}
                        if(islower(orig_symbol))
                        {
                                if(shiftvalue >= 26)
                                {
                                        tempvalue = shiftvalue % 26;
                                }else
                                {
                                        tempvalue = shiftvalue;
                                }
				new_symbol=((26 +orig_symbol-tempvalue - 97) % 26) + 97;//97 is the offset of ASCII
                                out_stream.put(new_symbol);
			}
                        if(isdigit(orig_symbol))
                        {
                                if(shiftvalue >= 10)
                                {
                                        tempvalue = shiftvalue % 10;
                                }else
                                {
                                        tempvalue = shiftvalue;
                                }
				new_symbol=((10 +orig_symbol-tempvalue - 48) % 10) + 48;//48 is the offset of ASCII
                                out_stream.put(new_symbol);
				
		        }
		}
		in_stream.get(orig_symbol);        	
	}
}
Last edited on
closed account (48T7M4Gy)
Well, as a suggestion I would get the file read and write process working as a separate test program.

You currently have 188 lines of code with mountains of processes going on which makes debugging basically a waste of time. You should narrow the problem down into a simple test module and then incorporate that into the main code. When it works.
pdgaming (39)
Lol, I think we are in the same class. Anyway, this is the decryption key is as follows:

((26 + int(c) - key - 65) % 26 + 65)

26 is # of letters.
int(c) is taking your letter and turning it into its ascii code.
subtract your key.
65 is the ascii code for capital 'A'.
%26 is to loop those letters.

change 65 to whatever ascii code you need to use.
Last edited on
Enoizat (1343)
The following version works, but it's very basic:

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/* ============================================================================
Name: homework4.cpp
Author: Robert Ehrlish
Version:
Copyright: 2017
Description: This program encrypts and decrypts
============================================================================ */
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <exception>
#include <fstream>
#include <iostream>
#include <string>

/* ============================================================================
Function: write my info
Parameters: none
Return: none void
Description: writes my info
============================================================================
*/
void outPut();
/* ============================================================================
Function: encrypt
Parameters: input and output
Return: none void
Description: encrypts plaintext
============================================================================
*/
void doEncrypt(std::ifstream& in_stream, std::ofstream& out_stream);
/* ============================================================================
Function: decrypt
Parameters: none
Return: none void
Description: decrypts ciphertext
============================================================================
*/
void doDecrypt(std::ifstream& in_stream, std::ofstream& out_stream);

void askForFileNames(char encdec, std::ifstream& in_stream,
                     std::ofstream& out_stream);

int main()
{

   outPut();

   std::cout << "Would you like to ENCRYPT or DECRYPT (E or D)? ";
   std::string response;
   std::cin >> response;

   while (response.at(0) != 'e' && response.at(0) != 'E'
          && response.at(0) != 'd' && response.at(0) != 'D')
   {
      std::cout << "Would you like to ENCRYPT or DECRYPT (E or D)? ";
      std::cin >> response;
   }

   std::ifstream in_stream;
   std::ofstream out_stream;
   askForFileNames(response.at(0), in_stream, out_stream);

   if(response.at(0) == 'e' || response.at(0) == 'E') //if they want to encrypt
   {
      doEncrypt(in_stream, out_stream);
   }

   if(response.at(0) == 'd' || response.at(0) == 'D') //if they want to decrypt
   {
      doDecrypt(in_stream, out_stream);
   }

   out_stream.close();
   in_stream.close();

   return 0;
}

void doEncrypt(std::ifstream& in_stream, std::ofstream& out_stream)
{
   std::cout << "YOU WANT TO ENCRYPT" << std::endl;
   std::cout << "Enter the numerical key (i.e., an integer) used to encrypt: ";
   int shiftvalue {0};
   std::cin >> shiftvalue;

   char orig_symbol {}, new_symbol {};
   while(in_stream >> std::noskipws >> orig_symbol)
   {
      new_symbol = orig_symbol;
      if(std::isupper(orig_symbol))
      {
         //65 is the offset of ASCII
         new_symbol=((orig_symbol+shiftvalue - 65) % 26) + 65;
      }
      if(std::islower(orig_symbol))
      {
         //97 is the offset of ASCII
         new_symbol=((orig_symbol+shiftvalue - 97) % 26) + 97;
      }
      if(std::isdigit(orig_symbol))
      {
         //48 is the offset of ASCII
         new_symbol=((orig_symbol+shiftvalue - 48) % 10) + 48;
      }
      out_stream << new_symbol;
   }
}

void doDecrypt(std::ifstream& in_stream, std::ofstream& out_stream)
{
   std::cout << "YOU WANT TO DECRYPT" << std::endl;
   std::cout << "Enter the numerical key (i.e., an integer) used to decrypt: ";
   int shiftvalue = 0;
   std::cin >> shiftvalue;

   char orig_symbol {}, new_symbol {};
   while(in_stream >> std::noskipws >> orig_symbol)
   {
      int tempvalue {};
      new_symbol = orig_symbol;
      if(isupper(orig_symbol))
      {
         if(shiftvalue >= 26)
         {
            tempvalue = shiftvalue % 26;
         } else {
            tempvalue = shiftvalue;
         }
         //65 is the offset of ASCII
         new_symbol=((26 + orig_symbol-tempvalue - 65) % 26) + 65;
      }
      if(islower(orig_symbol))
      {
         if(shiftvalue >= 26)
         {
            tempvalue = shiftvalue % 26;
         }else
         {
            tempvalue = shiftvalue;
         }
         //97 is the offset of ASCII
         new_symbol=((26 +orig_symbol-tempvalue - 97) % 26) + 97;
      }
      if(isdigit(orig_symbol))
      {
         if(shiftvalue >= 10)
         {
            tempvalue = shiftvalue % 10;
         }else
         {
            tempvalue = shiftvalue;
         }
         //48 is the offset of ASCII
         new_symbol=((10 +orig_symbol-tempvalue - 48) % 10) + 48;
      }
      out_stream << new_symbol;
   }
}

void outPut()
{
   std::cout << "+---------------------------------------------------------+\n";
   std::cout << "|            Computer Science and Engineering             |\n";
   std::cout << "|             CSCE 1030 - Computer Science I              |\n";
   std::cout << "|  Robert Ehrlish    rte0023    robertehrlish@my.unt.edu  |\n";
   std::cout << "+---------------------------------------------------------+\n";
}

void askForFileNames(char encdec, std::ifstream& in_stream,
                     std::ofstream& out_stream)
{
   std::string input, output;
   if(encdec == 'e') {
      std::cout << "Enter the name of your input file you want to encrypt: ";
      std::cin >> input;
      std::cout << "Enter the name of the output file to write the ciphertext: ";
      std::cin >> output;
   } else {
      std::cout << "Enter the name of your input file you want to decrypt: ";
      std::cin >> input;
      std::cout << "Enter the name of the output file to write the plaintext: ";
      std::cin >> output;
   }

   in_stream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
   try {
      in_stream.open(input, std::ios_base::in);
   } catch(...) {
      std::cerr << "Exception opening file: \"" << input << "\""
                << std::strerror(errno) << '\n';
   }

   out_stream.exceptions(std::ifstream::failbit | std::ifstream::badbit);
   try {
      out_stream.open(output, std::ios_base::out);
   } catch(...) {
      std::cerr << "Exception opening file: \"" << output << "\""
                << std::strerror(errno) << '\n';
   }
}


Note: code updated after having eliminated a try-catch block used for debugging.
Last edited on
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