/*
  * Filename: crypt.c
  * Authors(s): Roland (r.weirhowell@gmail.com)
  * Description: Perform caesar cipher cryptographic operations
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/

#include "crypt.h"

// Which of the two below functions is faster (find out!)
inline int mod(int a, int b)
{
	return (a % b + b) % b;
}


inline int fast_mod(int a, int b)
{
	const int result = a % b;
	return result >= 0 ? result : result + b;
}

// Below two functions do NOT work for lower case letters (fix this!)
void caesar_encrypt(char* str, int size, int key)
{
	for (int i = 0; i < size && str[i] != '\n'; i++)
		if (str[i] != ' ')
		{
			str[i] += key - 65;
			str[i] %= 26;
			str[i] += 65;
		}
}


void caesar_decrypt(char* str, int size, int key)
{
	for (int i = 0; i < size && str[i] != '\n'; i++)
		if (str[i] != ' ')
		{
			str[i] = str[i] - key - 65;
			str[i] = mod(str[i], 26);
			str[i] += 65;
		}
}