sub.cpp

The file is substitution cipher assistant.It Will display the ciphertext underneath the guessed plai

/*
 * sub.c - substitution cipher assistant
 *
 * Will display the ciphertext underneath the guessed plaintext, in
 * rows that are 50 columns wide each.  The user enters in letter
 * substitutions and can request for letter, digram, or trigram
 * frequencies.
 * 
 */

#include "sub.h"

// First letter is the most frequent, etc
static char rank_list[] = {'E', 'T', 'A', 'O', 'I', 'N', 'S', 'H', 'R',
					       'D', 'L', 'C', 'U', 'M', 'W', 'F', 'G', 'Y',
						   'P', 'B', 'V', 'K', 'J', 'X', 'Q', 'Z'};

// Frequencies of occurrence in English of each alphabet letter
static float freq_list[] = {0.082, 0.015, 0.028, 0.043, 0.127, 0.022, 0.020,
							0.061, 0.070, 0.002, 0.008, 0.040, 0.024, 0.067,
							0.075, 0.019, 0.001, 0.060, 0.063, 0.091, 0.028,
							0.010, 0.023, 0.001, 0.020, 0.001};

int main (int argc, char *argv[])
{
	short int	selection = 0;
	string		CiphertextFilename = "",
				PlaintextFilename = "",
				Ciphertext = "",
				Plaintext = "";
	string		CiphertextSequence = "";		// For digram/trigram/sequence
												// frequency analyses
	char		CipherLetter = ' ',
				PlaintextLetter= ' ';
	float		frequency = 0.0;
				
		
	if (argc != 3)
	{
		cout << "Usage: sub <ciphertext-file> <plaintext-file>" << endl;
		exit(1);
	}
	
	// Put argv[1] and argv[2] into CiphertextFilename and PlaintextFilename
	CiphertextFilename.assign(argv[1]);
	PlaintextFilename.assign(argv[2]);

	// Read ciphertext into an array, cutting out all of the whitespace
	Ciphertext = read_ciphertext_into_string (CiphertextFilename);

	// Now that we know the size of the Ciphertext, copy that many -'s
	// into the plaintext string to sort of "initialize" it for display
	Plaintext.assign(Ciphertext.size(), '-');
	
	// Everything works fine up to here for SURE
	for (;;)
	{
		// Display the texts for the user to see
		display_texts (Ciphertext, Plaintext);

		// Prompt for a decision
		selection = prompt_user();

		switch (selection)
		{
			case 0:
				cout << "Exiting..." << endl;
				exit (1);
				break;
				
			// "Assign ciphertext letter to plaintext letter"
			case 1:
				// Prompt for ciphertext letter assignment
				cout << "Enter ciphertext letter to change: ";
				cin >> CipherLetter;
				// Prompt for plaintext letter to assign
				cout << "Enter plaintext letter to assign to " << CipherLetter << ": ";
				cin >> PlaintextLetter;
				cout << "Exchanging all occurrences of " << CipherLetter << " in the ciphertext "
					 << "with " << PlaintextLetter << "." << endl;

				assign_letter (CipherLetter, &Ciphertext, PlaintextLetter, &Plaintext);
				break;
				
			// "Display letter frequency"
			case 2:
				// Prompt for ciphertext letter to count
				cout << "Enter ciphertext letter to count: ";
				cin >> CipherLetter;
				cout << "Analyzing ciphertext for frequency of \"" << CipherLetter << "\"..." << endl;

				frequency = get_letter_frequency (CipherLetter, Ciphertext);

				// Set float to max of four decimal digits
				cout.precision(4);

				cout << "Frequency of occurrence of this letter was " << frequency << " (" << frequency*100 << "%)" << endl;
				break;

			// "Display frequencies of ALL letters"
			case 3:
				display_all_frequencies (Ciphertext);
				break;

			// "Display sequence frequency (arbitrary length)"
			case 4:
				// Prompt for ciphertext sequence
				cout << "Enter ciphertext sequence to count: ";
				cin >> CiphertextSequence;
				cout << "Analyzing ciphertext for frequency of \"" << CiphertextSequence << "\"..." << endl;

				frequency = get_sequence_frequency (CiphertextSequence, Ciphertext);

				// Set float to max of four decimal digits
				cout.precision(4);

				cout << "Frequency of occurrence of this letter was " << frequency << " {" << frequency*100 << "%)" << endl;
				break;
				
				
			// "Write plaintext to file"
			case 5:
				cout << "Writing to file " << PlaintextFilename << "." << endl;
				write_plaintext_to_file (PlaintextFilename, Plaintext);
				break;
				

			default:
				// Display menu again, entered non-valid choice
				break;
		}
	}
		
	// Should never get here of course, but I specified
	// a return of "int", so ... here it is.
	return 0;
}