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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';
}
}
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