Introduction to Network Security – Part 5

NOTIFICATION: These examples are provided for educational purposes. The use of this code and/or information is under your own responsibility and risk. The information and/or code is given ‘as is’. I do not take responsibilities of how they are used.

Symmetric Encryption

In the symmetric encryption, the same key (normally a single-key) is used to perform the encryption and decryption of the ciphertext.

Symmetric Cipher Model: This model is performed by performing transformations and substitutions on the plaintext. A secret key, independent from the plaintext and the algorithm, is used to cipher the plaintext. After, the ciphertext plus the secret key is used with the decryption algorithm to obtain the original plaintext.

Symmetric Encryption is the opposite to the concept of public key distribution which will be explained in future postings.

Requirements:

  1. The cipher model must be mathematical expression:
    (E: Encryption, D: Decryption, X: plaintext, Y: ciphertext, K: secret key)

    Y = E(K, X)
    X = D(K, Y)
    
  2. Assumption that the encryption algorithm is known to the attacker.
  3. A strong encryption algorithm which in case the attacker would obtain or know some examples of the ciphertext and the plaintext produced from the ciphertext, the attacker would still be not able to obtain the key. This means that if the attacker would obtain the ciphertext, the attacker would not be able to obtain the secret key or the plain text.
  4. Secret key should be known only by the sender and the receiver of the ciphertext.
  5. The distribution of the secret key must be done in a secure fashion. For example, the use of a third party that would generate and provide in a secure way the key to the sender and the receiver.

Substitution Ciphers

In classical substitution ciphers, all the letters in the plaintext will be replaced by another letter, number, and/or symbol.

Caesar Cipher

History explains that Julius Caesar <http://www.roman-empire.net/republic/caesar-index.html> came up with a substitution cipher that he used in his campaigns for military affairs.

The cipher works in the following way:

  1. We use the alphabet of 26 letters:
    
    
  2. Under this alphabet, we will rewrite the alphabet by picking a letter as a starting point.
    Lets say our key indicate the starting point such as K = 4 so we begin with the letter ‘E’ then:
  3. This means that if we wish to send a plaintext (P) that says HELLO, the ciphertext (C) would be LIPPS, and the key (K) would be 4
  4. The mathematical way to represent this cipher will be the follows:
    1. Give each letter of the alphabet a number:
      A = 1, B = 2, C = 3, D = 4, E = 5,F = 6, G = 7, H = 8, J = 9, K = 10, L = 11, M = 12, N = 13, O = 14,P = 15, Q = 16, R = 17, S = 18, T = 19, U = 20, V = 21, W = 22, X = 23, Y = 24, Z = 25.
    2. Encryption Algorithm:
      E: Encryption, Ct: Ciphertext, Pt: Plaintext, K: secret key

      Ct = E(Pt)
         = (Pt + K) mod 26
    3. Decryption Algorithm:
      D: Decryptor, Ct: Ciphertext, Pt: Plaintext, K: secret key

      Pt = D(Ct)
         = (26 + (Ct - K)) mod 26
  5. The weakness of this cipher is that it can be broken by brute force. We just need to test the 25 combinations of different keys  until we find the key that reveals the message.

Monoalphabetic Cipher

The mono-alphabetic cipher instead of shifting the alphabet a number of letters, its substitute each letter arbitrarily by mapping the plaintext letter map to a random arranged ciphertext. The only requirement for the ciphertext is that the letters must not be repeated.

Since we are using 26 letters of the alphabet the arrangement of the cipher can permute a total of 26! permutations.

If we wish to encode the word “HELLO”, we would obtain “NERRS”

Lets assume we wish to cipher a plaintext:

Plaintext = “THIS IS A SECRET MESSAGE ENCODED IN MONOALPHABETIC”

Ciphertext = “XNMW MW E WIGBIX OIWWEJI IPGSCIC MP OSPSERUEDIXMG”

The following website let you play a little with monoalphabetic cipher by randomizing for you the ciphertext:
<http://www.simonsingh.net/The_Black_Chamber/generalsubstitutionWithMenu.html>

The only problem is that this cipher can be exploited by doing regularities analysis over the frequency of the letters. Base on the language rules some letters are used more than others. For example, in English, the letter ‘E’ is the most common used in words, followed by A, I, O, N, R, S, T. Others letters such as K, J, Q, X, Z are less used than the rest.

The largest is the message, the most chances that the attacker can decrypt the message.
Just in this message “XNMW MW E WIGBIX OIWWEJI IPGSCIC MP OSPSERUEDIXMG” we have:

  • W = 6 letters
  • E = 4 letters
  • M = 4 letters
  • S = 3 letters
  • P = 2 letters
  • ….

And continue counting.

As you may notice the letter ‘W’ of the encrypted message have the most counts, so we could  assume that this is the letter E of the plaintext.

If you are interested to know the frequency of letters in English you can go to the following website:
<http://www.cryptograms.org/letter-frequencies.php>

For more information about attacking mono-alphabetic cipher, there is a good example on this website:
<http://unsecure.co.uk/attackingmonoalphabeticciphers.asp>

Playfair Cipher

Playfair is one way to improve the security of mono-alphabetic cipher by encrypting multiple letters.

Playfair Encryption

  1. Create a playfair key matrix:
    1. Create a matrix of letters based on a keyword. For this example, the matrix should be 5 by 5
    2. Fill in the letters of the keyword from left to right and from top to bottom. Make sure that there are not duplicate letters
    3. Fill the rest of the matrix with the other letters that are not in the keyboard, making sure to not duplicate letters.
    4. As a rule, the letter I and J count as one letter.
      • I am not sure the reason for this rule, except the following:
        • First, it make it harder to decrypt the message since one letter is missing.
        • Second, in some languages, the J and I would have the same pronunciation.
          For example, my last name Carlstein was originally written as Karlštejn.
      • In case you know the real reason, please let me know and give me a reference to verify (thanks).
    5. Example of playfair key matrix:
      1. Let use the keyword: “EDUCATOR”
      2. The table should looks like this:
      3. Notice that I and J are counted as one letter
  2. The next step is to encrypt the plaintext taking two letters at the time.
    1. In case a two letters are the same (repeated), we must insert a filler letter (use the letter X as the filler). For example:
      HELLO → HE LX LO
    2. In case two letters are in the same row, replace each letter with the letter to the right. In case the letter is at the last column, pick the letter of the first row (the table is considerate to be circular). For example, lets say we have the letters D and A:

      1. D → U and A → E
      2. Therefore DA became UE
    3. In case two letters are in the same column, replace each letter with the letter below. In case the letter is at the last row, pick the letter of the first row (the table is considerate to be circular). For example, lets say we have the letters T and V:

      1. T → G and V → E
      2. Therefore TV became GE
    4. In case two letter are in different row and column, the first letter will be replaced with another letter of the same row on the column of the second letter. The second letter will be replaced with another letter of the same row on the column of the first letter. For example lets say we have the letters O and Q:

      1. To replace the letter O:
        1. This means that O → B
      2. To replace the letter Q:
        1. This means that Q → N
      3. Therefore OQ became BN

Playfair Decryption:

  1. Decrypt two letters at a time:
    1. In case two letters are in the same row, replace each letter with the letter to the left. In case the letter is at the last column, pick the letter of the first row (the table is considerate to be circular). For example, lets say we have the letters U and E:

      1. U → D and E → A
      2. Therefore UE became DA
    2. In case two letters are in the same column, replace each letter with the letter above. In case the letter is at the last row, pick the letter of the first row (the table is considerate to be circular). For example, lets say we have the letters G and E:

      1. G → T and E → V
      2. Therefore GE became TV
    3. In case two letter are in different row and column, the first letter will be replaced with another letter of the same row on the column of the second letter. The second letter will be replaced with another letter of the same row on the column of the first letter. For example lets say we have the letters B and N:

      1. To replace the letter B:
        1. This means that O → B
      2. To replace the letter Q:
        1. This means that Q → N
      3. Therefore OQ became BN
  2. After you will finish with the final message. You must remove any extra X that do not make sense in the message:
    HE LX LO → HELLO
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Count all Alphabetics Characters Existent in the String

Process input file by Count all alphabetic characters existent in the string.

I would advice to compile them in Linux as I did.

NOTIFICATION: These examples are provided for educational purposes. Using this code is under your own responsibility and risk. The code is given ‘as is’. I do not take responsibilities of how they are used.

StreamOperation.h:

#ifndef STREAM_OPERATION_H
#define STREAM_OPERATION_H

#include <iostream>		// for cout

#include <fstream>		// for ifstream, ofstream

#include <string>       // for String
#include <cctype>       // for classify and transform individual characters

using namespace std;

/**
 * author: Alejandro G. Carlstein
 * Class: StreamOperation
 * Description: This class will read a textfile and produce an output
 *				in another text file. The other text file will contain
 * 				a copy of the input file but all blank lines will be
 *				removed, the lines are going to be numbered, all
 *              semicolons will be replaces with the string 'SEMI-COLON',
 *				print the number of lines removed at the second to last
 *              line, and finally print the number of alphabetic characters
 */
class StreamOperation {

private:   

	bool doRemoveBlankLines;

	bool doReplaceAllStrings;

	bool doCountLines;	

	int numLinesRemoved;

	int numAlphaCharacters;

	string oldStr;

	string newStr;

	void replaceAll(string& str,
					string oldStr,
					string newStr);

	int countAlphaCharacters(string str);

	void copyStream(ifstream& fin,
			  		ofstream& fout);

public:

	// Default constructor
	StreamOperation(void);

	// * Get Methods *

	// Get the number of lines removed
	int getNumberLinesRemoved();

	// Get the number of alphabetic character
	int getNumberAlphaCharacters();

	// * Set Methods * 	

	// * Print Methods *

	// Print the number of blank lines removed
	void printNumberLinesRemoved(ofstream& output);		

	// Print the number of alphabetic characters
	void printNumberAlphaCharacters(ofstream& output);		

	// * Process Methods *

	// Copy the content from an input stream to an output stream
	void copy(ifstream& input,
			  ofstream& output);	

	// Copy the content from an input stream to an output stream.
    // This method can remove all the blank lines in the output
    // stream when copying.
	void copy(ifstream& input,
			  ofstream& output,
			  bool removeBlankLines);

	// Copy the content from an input stream to an output stream.
	// This method can remove all the blank lines in the output
 	// stream when copying.
	// This method can number all the lines in the output stream.
	void copy(ifstream& input,
			  ofstream& output,
			  bool removeBlankLines,
              bool numberLines);

	// Copy the content from an input stream to an output stream.
	// This method can replace all old strings for a new string
	// This method can remove all the blank lines in the output
 	// stream when copying.
	// This method can number all the lines in the output stream.
	void copy(ifstream& input,
			  ofstream& output,
              string oldString,
			  string newString,
			  bool removeBlankLines,
			  bool numberLines);

    // Default destructor
	~StreamOperation(void);
};

#endif

StreamOperation.cpp:

/**
 * author: Alejandro G. Carlstein  
 * Class: StreamOperation
 * Description: This class will read a textfile and produce an output
 *		in another text file. The other text file will contain
 * 		a copy of the input file but all blank lines will be
 *		removed, the lines are going to be numbered, all
 *              semicolons will be replaces with the string 'SEMI-COLON',
 *		print the number of lines removed at the second to last
 *              line, and finally print the number of alphabetic characters
 */

#include 'StreamOperation.h'

/**
 * Public Methods
 */

/**
 * StreamOperation
 * @description: Default Constructor
 */
StreamOperation::StreamOperation(void){

	numLinesRemoved = 0;

	numAlphaCharacters = 0;

	doRemoveBlankLines = false;

	doReplaceAllStrings = false;

	doCountLines = false;

	oldStr = '';

	newStr = '';

}

// * Get Methods *

/**
 * getNumberLinesRemoved
 * @description: Get the number of lines removed
 * @return: integer
*/
int StreamOperation::getNumberLinesRemoved(){
	return numLinesRemoved;
}

/**
 * getNumberAlphaCharacters
 * @description: Get the number of alphabetic character
 * @return: integer
 */
int StreamOperation::getNumberAlphaCharacters(){
	return numAlphaCharacters;
}

// * Set Methods *

// * Print Methods *

// Print the number of blank lines removed
void StreamOperation:RazzrintNumberLinesRemoved(ofstream& output){
	if (output.is_open()){
		output << numLinesRemoved;
	} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
	}
}

// Print the number of alphabetic characters
void StreamOperation:RazzrintNumberAlphaCharacters(ofstream& output){
	if (output.is_open()){
		output << numAlphaCharacters;
	} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
	}
}

// * Process Methods *

/**
 * copy
 * @description: Copy the content from an input stream to an output stream
 * @param: input, output
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output){

	doRemoveBlankLines = false;

	doReplaceAllStrings = false;

	doCountLines = false;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *
 * @param: input, output, removeBlankLines
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output,
						   bool removeBlankLines){

	doReplaceAllStrings = false;

	doCountLines = false;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: input, output, removeBlankLines, numberLines
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output,
						   bool removeBlankLines,
						   bool numberLines){

	doReplaceAllStrings = false;

	doCountLines = numberLines;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *				 This method can replace all old strings for a new string
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: input, output, oldstring, new string, removeBlankLines, numberLines
 */
void StreamOperation::copy(ifstream& input,
			  			   ofstream& output,
			               string oldString,
			 			   string newString,
			  			   bool removeBlankLines,
						   bool numberLines){

	doReplaceAllStrings = true;

	oldStr = oldString;

	newStr = newString;

	doCountLines = numberLines;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * StreamOperation
 * @description: Default Destructor
 */
StreamOperation::~StreamOperation(void){
};

/**
 * Private Methods
 */

/**
 * replaceAll
 * @description: This method will remove all substrings for a new substring
 *               inside the string
 * @param: str, oldStr, newStr
 */
void StreamOperation::replaceAll(string& str,
			   		  			 string oldStr,
				  	  			 string newStr){

	// The method find return the unsigned int string::npos
    // if substring not found. Therefore, string::size_type
	// type is used
	string::size_type position = 0;

	// Until the end of the string is reached, search for every
    // string that maches the old string and replace it with
	// the new string.
	while((position = str.find(oldStr, position)) != string::npos){
		str.replace(position,
					oldStr.length(),
					newStr);
		position++;
	}
}

/**
 * countAlphaCharacters
 * @description: Count all alphabetics characters existent in the string
 * @param: str
 * @return: integer
 */
int StreamOperation::countAlphaCharacters(string str){

	int countAlpha = 0;

	// Go thought the whole string, counting all
	// the alphabetic characters
	for (int position = 0;
		 position < str.length();
		 position++){

		countAlpha += (isalpha(str[position]) ? 1 : 0);

	}

	return countAlpha;
}

/**
 * copyStream
 * @description: This method copy the content from an input stream to
 *               an output stream.
 *				 Base on the flags doRemoveBlankLines, doCountLines, and
 *               doReplaceAllStrings:
 *				 This method can replace all old strings for a new string
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: fin, fout
 */
void StreamOperation::copyStream(ifstream& fin,
							     ofstream& fout){
	int lineCounter;

	string strBuffer;

	numLinesRemoved = 0;

	numAlphaCharacters = 0;	

	lineCounter = 1;

	// Check if input and output stream can be open
	if (fin.is_open()){

		if (fout.is_open()){	

			//Read one line at the time as a string until eof
			while(!fin.eof()){

				getline(fin, strBuffer);

				// If the string is empty and doRemoveBlankLines
				// is true, count the string as as a blank line
				// else process the string
				if (strBuffer.empty() && doRemoveBlankLines){

					numLinesRemoved++;

				}else{

					// Count the alphabetic character of the string
					numAlphaCharacters += countAlphaCharacters(strBuffer);

					// Replace all semicolons with the string SEMICOLON
					if (doReplaceAllStrings)
						replaceAll(strBuffer, oldStr, newStr);

					// Add a number to each line if doCountLines is true
					if (doCountLines)
						fout << lineCounter++ << ' ';					

					fout << strBuffer << endl;

				}

			}

		} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
		}

	}else{
		cerr << '[X] Error: Program cannot read file!' << endl
			 << 'Exit Program!' << endl;
	}

}

processFile.cpp:

/**
 * Author: Alejandro G. Carlstein
 * Description: Use the file StreamOperations.cpp as an input file
 *				and process it using StreamOperation class
 */

#include <iostream>
#include <fstream>
#include 'StreamOperation.h'

static const string INPUT_FILE = 'StreamOperation.cpp';
static const string OUTPUT_FILE = 'Output.txt';
static const string SEMI_COLON = ';';
static const string STR_SEMI_COLON = 'SEMI-COLON';

/**
 * Main function
 * @param: argc, argv
 */

int main(int argc, char *argv[]){

	ifstream inputFile;
	ofstream outputFile;

	// If the program is executed with two parameters (file 1  and file 2)
    // used these parameters as input file and output file
	// If the program is executed without parameters use default files
    // If the program is executed with the -h parameter display help
	// If the program get more than two parameters or
    // wrong key display help
	if (argc == 1 || argc == 3){

		if (argc == 1){

			inputFile.open(INPUT_FILE.data());

			outputFile.open(OUTPUT_FILE.data());	

		}else{

			inputFile.open(argv[1]);

			outputFile.open(argv[2]);
		}

		StreamOperation StrOp;

		// Copy the content from the input file to the output file
	    // In the process, replace the ; with string SEMI-COLON,
		// remove the blank lines and number all the lines
		StrOp.copy(inputFile,
				   outputFile,
				   SEMI_COLON,
				   STR_SEMI_COLON,
				   true,
	               true);

		outputFile << 'Lines Removed: '
				   << StrOp.getNumberLinesRemoved() << endl;

		outputFile << 'Alphabetic Characters: '
				   << StrOp.getNumberAlphaCharacters();

		inputFile.close();

		outputFile.close();

	} else {
		cout << argv[0] << ' input_file output_file ' << endl;
	}	

	return 0;
}

input.txt:

23
This is
An example

of things;
That we can input;

;; aaa ;

output.txt:

1 23
2 This is
3 An example
4 of thingsSEMI-COLON
5 That we can inputSEMI-COLON
6 SEMI-COLONSEMI-COLON aaa SEMI-COLON

If you encounter any problems or errors, please let me know by providing an example of the code, input, output, and an explanation. Thanks.

/**
* author: Alejandro G. Carlstein
* Course: CS 240
* Class: StreamOperation
* Description: This class will read a textfile and produce an output
*        in another text file. The other text file will contain
*         a copy of the input file but all blank lines will be
*        removed, the lines are going to be numbered, all
*              semicolons will be replaces with the string ‘SEMI-COLON’,
*        print the number of lines removed at the second to last
*              line, and finally print the number of alphabetic characters
*/

#include “StreamOperation.h”

/**
* Public Methods
*/

/**
* StreamOperation
* @description: Default Constructor
*/
StreamOperation::StreamOperation(void){

numLinesRemoved = 0;

numAlphaCharacters = 0;

doRemoveBlankLines = false;

doReplaceAllStrings = false;

doCountLines = false;

oldStr = “”;

newStr = “”;

}

// * Get Methods *

/**
* getNumberLinesRemoved
* @description: Get the number of lines removed
* @return: integer
*/
int StreamOperation::getNumberLinesRemoved(){
return numLinesRemoved;
}

/**
* getNumberAlphaCharacters
* @description: Get the number of alphabetic character
* @return: integer
*/
int StreamOperation::getNumberAlphaCharacters(){
return numAlphaCharacters;
}

// * Set Methods *

// * Print Methods *

// Print the number of blank lines removed
void StreamOperation:RazzrintNumberLinesRemoved(ofstream& output){
if (output.is_open()){
output << numLinesRemoved;
} else {
cerr << “[X] Error: Program cannot write file!” << endl
<< “Exit program!” << endl;
}
}

// Print the number of alphabetic characters
void StreamOperation:RazzrintNumberAlphaCharacters(ofstream& output){
if (output.is_open()){
output << numAlphaCharacters;
} else {
cerr << “[X] Error: Program cannot write file!” << endl
<< “Exit program!” << endl;
}
}

// * Process Methods *

/**
* copy
* @description: Copy the content from an input stream to an output stream
* @param: input, output
*/
void StreamOperation::copy(ifstream& input,
ofstream& output){

doRemoveBlankLines = false;

doReplaceAllStrings = false;

doCountLines = false;

copyStream(input, output);

}

/**
* copy
* @description: Copy the content from an input stream to an output stream.
*               This method can remove all the blank lines in the output
*                 stream when copying.
*
* @param: input, output, removeBlankLines
*/
void StreamOperation::copy(ifstream& input,
ofstream& output,
bool removeBlankLines){

doReplaceAllStrings = false;

doCountLines = false;

doRemoveBlankLines = removeBlankLines;

copyStream(input, output);

}

/**
* copy
* @description: Copy the content from an input stream to an output stream.
*               This method can remove all the blank lines in the output
*                 stream when copying.
*               This method can number all the lines in the output stream.
* @param: input, output, removeBlankLines, numberLines
*/
void StreamOperation::copy(ifstream& input,
ofstream& output,
bool removeBlankLines,
bool numberLines){

doReplaceAllStrings = false;

doCountLines = numberLines;

doRemoveBlankLines = removeBlankLines;

copyStream(input, output);

}

/**
* copy
* @description: Copy the content from an input stream to an output stream.
*                 This method can replace all old strings for a new string
*               This method can remove all the blank lines in the output
*                 stream when copying.
*               This method can number all the lines in the output stream.
* @param: input, output, oldstring, new string, removeBlankLines, numberLines
*/
void StreamOperation::copy(ifstream& input,
ofstream& output,
string oldString,
string newString,
bool removeBlankLines,
bool numberLines){

doReplaceAllStrings = true;

oldStr = oldString;

newStr = newString;

doCountLines = numberLines;

doRemoveBlankLines = removeBlankLines;

copyStream(input, output);

}

/**
* StreamOperation
* @description: Default Destructor
*/
StreamOperation::~StreamOperation(void){
};

/**
* Private Methods
*/

/**
* replaceAll
* @description: This method will remove all substrings for a new substring
*               inside the string
* @param: str, oldStr, newStr
*/
void StreamOperation::replaceAll(string& str,
string oldStr,
string newStr){

// The method find return the unsigned int string::npos
// if substring not found. Therefore, string::size_type
// type is used
string::size_type position = 0;

// Until the end of the string is reached, search for every
// string that maches the old string and replace it with
// the new string.
while((position = str.find(oldStr, position)) != string::npos){
str.replace(position,
oldStr.length(),
newStr);
position++;
}
}

/**
* countAlphaCharacters
* @description: Count all alphabetics characters existent in the string
* @param: str
* @return: integer
*/
int StreamOperation::countAlphaCharacters(string str){

int countAlpha = 0;

// Go thought the whole string, counting all
// the alphabetic characters
for (int position = 0;
position < str.length();
position++){

countAlpha += (isalpha(str[position]) ? 1 : 0);

}

return countAlpha;
}

/**
* copyStream
* @description: This method copy the content from an input stream to
*               an output stream.
*                 Base on the flags doRemoveBlankLines, doCountLines, and
*               doReplaceAllStrings:
*                 This method can replace all old strings for a new string
*               This method can remove all the blank lines in the output
*                 stream when copying.
*               This method can number all the lines in the output stream.
* @param: fin, fout
*/
void StreamOperation::copyStream(ifstream& fin,
ofstream& fout){
int lineCounter;

string strBuffer;

numLinesRemoved = 0;

numAlphaCharacters = 0;

lineCounter = 1;

// Check if input and output stream can be open
if (fin.is_open()){

if (fout.is_open()){

//Read one line at the time as a string until eof
while(!fin.eof()){

getline(fin, strBuffer);

// If the string is empty and doRemoveBlankLines
// is true, count the string as as a blank line
// else process the string
if (strBuffer.empty() && doRemoveBlankLines){

numLinesRemoved++;

}else{

// Count the alphabetic character of the string
numAlphaCharacters += countAlphaCharacters(strBuffer);

// Replace all semicolons with the string SEMICOLON
if (doReplaceAllStrings)
replaceAll(strBuffer, oldStr, newStr);

// Add a number to each line if doCountLines is true
if (doCountLines)
fout << lineCounter++ << ” “;

fout << strBuffer << endl;

}

}

} else {
cerr << “[X] Error: Program cannot write file!” << endl
<< “Exit program!” << endl;
}

}else{
cerr << “[X] Error: Program cannot read file!” << endl
<< “Exit Program!” << endl;
}

}

/**
 * author: Alejandro G. Carlstein
 * Course: CS 240
 * Class: StreamOperation
 * Description: This class will read a textfile and produce an output
 *		in another text file. The other text file will contain
 * 		a copy of the input file but all blank lines will be
 *		removed, the lines are going to be numbered, all
 *              semicolons will be replaces with the string 'SEMI-COLON',
 *		print the number of lines removed at the second to last
 *              line, and finally print the number of alphabetic characters
 */

#include 'StreamOperation.h'

/**
 * Public Methods
 */

/**
 * StreamOperation
 * @description: Default Constructor
 */
StreamOperation::StreamOperation(void){

	numLinesRemoved = 0;

	numAlphaCharacters = 0;

	doRemoveBlankLines = false;

	doReplaceAllStrings = false;

	doCountLines = false;

	oldStr = '';

	newStr = '';

}

// * Get Methods *

/**
 * getNumberLinesRemoved
 * @description: Get the number of lines removed
 * @return: integer
*/
int StreamOperation::getNumberLinesRemoved(){
	return numLinesRemoved;
}

/**
 * getNumberAlphaCharacters
 * @description: Get the number of alphabetic character
 * @return: integer
 */
int StreamOperation::getNumberAlphaCharacters(){
	return numAlphaCharacters;
}

// * Set Methods *

// * Print Methods *

// Print the number of blank lines removed
void StreamOperation:RazzrintNumberLinesRemoved(ofstream& output){
	if (output.is_open()){
		output << numLinesRemoved;
	} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
	}
}

// Print the number of alphabetic characters
void StreamOperation:RazzrintNumberAlphaCharacters(ofstream& output){
	if (output.is_open()){
		output << numAlphaCharacters;
	} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
	}
}

// * Process Methods *

/**
 * copy
 * @description: Copy the content from an input stream to an output stream
 * @param: input, output
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output){

	doRemoveBlankLines = false;

	doReplaceAllStrings = false;

	doCountLines = false;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *
 * @param: input, output, removeBlankLines
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output,
						   bool removeBlankLines){

	doReplaceAllStrings = false;

	doCountLines = false;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: input, output, removeBlankLines, numberLines
 */
void StreamOperation::copy(ifstream& input,
						   ofstream& output,
						   bool removeBlankLines,
						   bool numberLines){

	doReplaceAllStrings = false;

	doCountLines = numberLines;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * copy
 * @description: Copy the content from an input stream to an output stream.
 *				 This method can replace all old strings for a new string
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: input, output, oldstring, new string, removeBlankLines, numberLines
 */
void StreamOperation::copy(ifstream& input,
			  			   ofstream& output,
			               string oldString,
			 			   string newString,
			  			   bool removeBlankLines,
						   bool numberLines){

	doReplaceAllStrings = true;

	oldStr = oldString;

	newStr = newString;

	doCountLines = numberLines;

	doRemoveBlankLines = removeBlankLines;

	copyStream(input, output);

}

/**
 * StreamOperation
 * @description: Default Destructor
 */
StreamOperation::~StreamOperation(void){
};

/**
 * Private Methods
 */

/**
 * replaceAll
 * @description: This method will remove all substrings for a new substring
 *               inside the string
 * @param: str, oldStr, newStr
 */
void StreamOperation::replaceAll(string& str,
			   		  			 string oldStr,
				  	  			 string newStr){

	// The method find return the unsigned int string::npos
    // if substring not found. Therefore, string::size_type
	// type is used
	string::size_type position = 0;

	// Until the end of the string is reached, search for every
    // string that maches the old string and replace it with
	// the new string.
	while((position = str.find(oldStr, position)) != string::npos){
		str.replace(position,
					oldStr.length(),
					newStr);
		position++;
	}
}

/**
 * countAlphaCharacters
 * @description: Count all alphabetics characters existent in the string
 * @param: str
 * @return: integer
 */
int StreamOperation::countAlphaCharacters(string str){

	int countAlpha = 0;

	// Go thought the whole string, counting all
	// the alphabetic characters
	for (int position = 0;
		 position < str.length();
		 position++){

		countAlpha += (isalpha(str[position]) ? 1 : 0);

	}

	return countAlpha;
}

/**
 * copyStream
 * @description: This method copy the content from an input stream to
 *               an output stream.
 *				 Base on the flags doRemoveBlankLines, doCountLines, and
 *               doReplaceAllStrings:
 *				 This method can replace all old strings for a new string
 *               This method can remove all the blank lines in the output
 *				 stream when copying.
 *               This method can number all the lines in the output stream.
 * @param: fin, fout
 */
void StreamOperation::copyStream(ifstream& fin,
							     ofstream& fout){
	int lineCounter;

	string strBuffer;

	numLinesRemoved = 0;

	numAlphaCharacters = 0;	

	lineCounter = 1;

	// Check if input and output stream can be open
	if (fin.is_open()){

		if (fout.is_open()){	

			//Read one line at the time as a string until eof
			while(!fin.eof()){

				getline(fin, strBuffer);

				// If the string is empty and doRemoveBlankLines
				// is true, count the string as as a blank line
				// else process the string
				if (strBuffer.empty() && doRemoveBlankLines){

					numLinesRemoved++;

				}else{

					// Count the alphabetic character of the string
					numAlphaCharacters += countAlphaCharacters(strBuffer);

					// Replace all semicolons with the string SEMICOLON
					if (doReplaceAllStrings)
						replaceAll(strBuffer, oldStr, newStr);

					// Add a number to each line if doCountLines is true
					if (doCountLines)
						fout << lineCounter++ << ' ';					

					fout << strBuffer << endl;

				}

			}

		} else {
			cerr << '[X] Error: Program cannot write file!' << endl
				 << 'Exit program!' << endl;
		}

	}else{
		cerr << '[X] Error: Program cannot read file!' << endl
			 << 'Exit Program!' << endl;
	}

}
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