#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

void encryption(char *name,int key);
void decryption(char *name,int key);
void clr();

int main()
{
    char *name=(char*)malloc(20*sizeof(char));
	int choice;
	int key;

   	do
	{
		clr();
		printf("1.Encrypt File\n");
		printf("2.Decrypt File\n");
        printf("3.Encryption/Decryption key\n");
		scanf("%d",&choice);
		if(choice==1)
		{
			clr();
			encryption(name,key);
		}
		else if(choice==2)
		{
			clr();
			decryption(name,key);
		}
        else if(choice==3)
        {
             clr();
             printf("key : ");
             scanf("%d",&key);
             main();
        }
	} while((choice!=1) && (choice!=2) && (choice!=3));
    free(name);
 
}
void encryption(char *name,int key)
{
     FILE *ein;
     FILE *eout;
     int einBuffer;
	 ein=NULL;
     
	 while(ein==NULL)
	 {

		 printf("Enter the filename...\n");
		 scanf("%s",name);
		 ein=fopen(name,"r");
		 if(ein!=NULL)
		 {
			eout=fopen("tmp_encrypted","w");
			while((feof(ein))==0)
			{
				einBuffer=fgetc(ein);
				einBuffer^=key;
				fprintf(eout,"%c",einBuffer);             
			}
		 }
	     else
		 {
			printf("Can't open file...\n");
		 } 
	 }
	fclose(ein);
	fclose(eout);
    remove(name);
	rename("tmp_encrypted",name);
    main();
}

void decryption(char *name,int key)
{
     FILE *din;
     FILE *dout;
     int dinBuffer;
	 din=NULL;
     
	 while(din==NULL)
	 {
		 printf("Enter the filename...\n");
		 scanf("%s",name);
		 din=fopen(name,"r");
		 if(din!=NULL)
		 {
			dout=fopen("tmp_decrypted","w");
			while((feof(din))==0)
			{
				dinBuffer=fgetc(din);
				dinBuffer^=key;
				fprintf(dout,"%c",dinBuffer);
			 }
		 }
	     else
		 {
			printf("Can't open file...\n");
		 } 
	 }
	fclose(din);
	fclose(dout);
    remove(name);
	rename("tmp_decrypted",name);
    main();
}

void clr()
{
	system("cls");
}