//XOR Encrypt 0.1.0
//by Sean Kane - http://celtickane.com

#include <stdio.h>
#include <stdlib.h>	//malloc
#include <string.h> //strlen

#define MAX_SIZE 80	//change this if you want larger buffers

int main()
{
	char bufFileIn[MAX_SIZE], bufKey[MAX_SIZE], bufFileOut[MAX_SIZE]; //Buffers
	FILE *fpIn, *fpOut; //File pointers
	char *mp; //Pointer for malloc
	char chrPrompt, chrXOR; long fSize;
	int iKey, iFile; //Incremental variables for loops

	for (;;)
	{
		printf("(O)pen file, (I)nformation, (Q)uit: ");
		chrPrompt = getchar();
		
		switch ( chrPrompt )
		{
		case 'q': case 'Q': //Quit the program
			exit(1); //Exit with a return code of 1
			break;
		case 'o': case 'O': //Open a file
			//Read file for input
			fflush(stdin); //Clear out garbage from stdin
			printf("\nEnter filename for input: ");
			gets(bufFileIn); //Similar to scanf, but will include spaces
			fpIn = fopen(bufFileIn, "rb");
			if (fpIn == NULL) //file pointers return NULL if they errored
			{
				printf("\nUnable to access input file.\n\n");
				break;
			}
			
			//Read encryption key
			printf("Enter encryption key: ");
			gets(bufKey);

			//Prepare file for output
			printf("Enter filename for output: ");
			gets(bufFileOut);
			fpOut = fopen(bufFileOut, "wb");
			if (fpOut == NULL)
			{
				printf("\nUnable to write to output file.\n\n");
				break;
			}

			//Actually read the input file
			fseek(fpIn, 0, SEEK_END); //Seek to the end
			fSize = ftell(fpIn); //Sets fSize to total size of input file
			rewind(fpIn); //Start back at the beginning
			mp = (char*) malloc (fSize); //Allocate memory -- set location as mp (memory pointer)
			if (mp == NULL) //Couldn't allocate memory
			{
				printf("Unable to allocate necessary memory to open file.");
				exit(2);
			}
			fread (mp, 1, fSize, fpIn);
			
			//Display data and encrypt/decrypt (same thing)
			printf("\nFile input data:\n");
			for (iFile = 0; iFile < fSize; iFile++) 
			{
				printf("%c",mp[iFile]);
			}
			iKey = 0;
			printf("\n\nFile output data:\n");
			for (iFile = 0; iFile < fSize; iFile++)
			{
				chrXOR = mp[iFile] ^ bufKey[iKey];
				printf("%c", chrXOR);
				fputc(chrXOR, fpOut);
				(iKey == (strlen(bufKey) -1)) ? iKey = 0 : iKey++;
			}

			//Close everything up
			fclose(fpIn);
			fclose(fpOut);
			free(mp);
			printf("\n\nFile successfully written.\n\n");
			break;
		case 'i': case 'I':
			fflush(stdin); //Again, we need to clear the stdin buffer or it'll mess up
			printf("\nXOR Encrypt version 0.0.2 by Sean Kane\nhttp://celtickane.com/programming\n\n");		
			break;
		default:
			printf("Please type O, I, or Q.\n");
			break;
		} //End switch

	} //End for

	return 0;
}  //End main