// basic character-int conversions, the underlying idea behind most crypto

#include <iostream.h>
#include <stdio.h>
#include <conio.h>
#include <fstream.h>

#define CYPHER 999999
#define MAXLENGTH 1000

void encrypt();
void decrypt();
void show();

const char * filename = "msg.txt";

int main()
{
	char corn='5';

while (corn != '4')
{
	clrscr();
	cout << "\n-----------------------------------" << endl;
	cout << "        " << MAXLENGTH << " max chars " << endl;
	cout << "-----------------------------------" << endl;
	cout << "1) Encrypt text " << endl;
	cout << "2) Decrypt text " << endl;
	cout << "3) Show encrypted string" << endl;
	cout << "4) EXIT " << endl;
	cout << "\nselection : ";
	corn = getch();
	cout << corn;
	if (corn == '1')
		encrypt();
	else if (corn == '2')
		decrypt();
	else if (corn == '3')
		show();
}

	return 0;
}

void encrypt()
{
	char dummy;
	char encrypt[MAXLENGTH];
	for (long x=0;x<=MAXLENGTH;x++)
		encrypt[x] = NULL;
	fflush(stdin);
	cout << "\nEnter text to be encrypted: ";
	gets(encrypt);
	long stat=0;
	cout << endl << "processing your request..";
	ofstream file;
	file.open (filename);
	for (x=0;x<=MAXLENGTH;x++) {
		if ((long)encrypt[x] != NULL)
			file << (long)(encrypt[x] * CYPHER) << " ";
	}
	file << "0";
	file.close();
	cout << "\n\n\nencrypted text stored in " << filename;
	dummy = getch();
}

void decrypt()
{
	long l,m,key;
	ifstream filein;
	filein.open (filename);
	l = filein.tellg();
	filein.seekg (0, ios::end);
	m = filein.tellg();
//	cout << "\n..begining g: " << l << " bytes, ..end g: " << m << " bytes.\n";
	cout << "\nimported file is " << (m-l) << " bytes.\n\n";
	filein.seekg (0, ios::beg);
	long decrypt[MAXLENGTH];
	long count=0;

	for (long i=0;filein.good();i++) {
		filein >> key;
		decrypt[i] = key;
		count++;
	}
	for (i=0;i<count-2;i++)
		cout << (char)(decrypt[i] / CYPHER);
	filein.close();
	cout << "\n\n\nencrypted text stored in " << filename;
	char dummy = getch();
}

void show()
{
	long l,m,key;
	ifstream filein;
	filein.open (filename);
	l = filein.tellg();
	filein.seekg (0, ios::end);
	m = filein.tellg();
	cout << "\nimported file is " << (m-l) << " bytes.\n";
	filein.seekg (0, ios::beg);

	for (long i=0;filein.good();i++) {
		filein >> key;
		cout << key << " " << endl;
	}

	filein.close();
	cout << "\n\n\nencrypted text stored in " << filename;
	char dummy = getch();