#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/proc_fs.h>
#include<linux/sched.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/slab.h>

#define PROC_FILE_NAME "crypto_services"

unsigned char buffer[1024*1024];
int read_out = 0;
// This doesn't use offp properly, so don't copy this behavior!
ssize_t read_simple(struct file *filp,char *buf,size_t count,loff_t *offp ) 
{
	if(read_out){
		read_out = 0;
		return 0;
	}
	memcpy(buf, buffer, strlen(buffer));
	read_out = 1;
	return strlen(buffer);
}

unsigned int call_count = 0;
ssize_t write_simple(struct file *filp,const char *buf,size_t count,loff_t *offp)
{
	int i;
	strncpy(buffer, buf, count);
	buffer[count] = 0;
	printk("Write was called (%u)!  The user thinks they're going to write %s to a file.\n", call_count++, buffer);
	for(i = 0; i < count; i++){
		if(buffer[i] <= 90 && buffer[i] >= 65) { // uppercase	
			buffer[i] += 13;
			if(buffer[i] > 90)
				buffer[i] -= 26;
		}
		else if(buffer[i] <= 122 && buffer[i] >= 97) { // lowercase
			buffer[i] += 13;
			if(buffer[i] > 122)
				buffer[i] -= 26;
		}
	}
	printk("Encrypted: %s\n", buffer);
	return count;	
}

struct file_operations proc_fops = {
	read: read_simple,
	write: write_simple
};

int proc_init (void) {
	printk("We're in the kernel!\n");
	proc_create(PROC_FILE_NAME,0,NULL,&proc_fops);
	return 0;
}

void proc_cleanup(void) {
	remove_proc_entry(PROC_FILE_NAME,NULL);
}

MODULE_LICENSE("GPL"); 
module_init(proc_init);
module_exit(proc_cleanup);