/*
 * fib-module.c
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

static unsigned long long fibonacci(unsigned int n) {
	unsigned long long h,i,j,k,t;

	h = i = 1;
	j = k = 0;
	while (n > 0) {
		if (n&1) {
			t = j*h;
			j = i*h + j*k + t;
			i = i*k + t;
		}
		t = h*h;
		h = 2*k*h + t;
		k = k*k + t;
		n /= 2;
	}
	return j;
}

void *fib_start(struct seq_file *m, loff_t *pos) {
	return pos;
}

void fib_stop(struct seq_file *m, void *v) {
}

void *fib_next(struct seq_file *m, void *v, loff_t *pos) {
	if (++(*pos) >= 94)
		return NULL;
	return pos;
}

int fib_show(struct seq_file *m, void *v) {
	loff_t pos = * (loff_t *) v;

	if (pos >= 0 && pos < 94)
		seq_printf(m, "%llu\n", fibonacci(pos));
	return 0;
}

struct seq_operations fib_op = {
	.start    = fib_start,
	.stop     = fib_stop,
	.next     = fib_next,
	.show     = fib_show
};

static int fib_open(struct inode *inode, struct file *file) {
	return seq_open(file, &fib_op);
}

static struct file_operations proc_fib_operations = {
	.open      = fib_open,
	.read      = seq_read,
	.llseek    = seq_lseek,
	.release   = seq_release,
};

static int __init fib_init(void) {
	struct proc_dir_entry *proc_fib;

	proc_fib = create_proc_entry("fibonacci", 0666, NULL);
	if (!proc_fib)
		return 1;
	proc_fib->proc_fops = &proc_fib_operations;
	return 0;
}

static void __exit fib_exit(void) {
	remove_proc_entry("fibonacci", 0);
}

module_init(fib_init);
module_exit(fib_exit);
MODULE_LICENSE("GPL");