#include "sys.h"
#include "inode.h"
#include "proc.h"
#include "file.h"
#include "lock.h"

struct lock llist [NLOCK] = {0};

/*
 * lock system call
 */

reclock (fd, size)
	register int fd;
	register unsigned size;
	{
	static struct file *fp;
	static struct inode *ip;
	static struct lock *l, *new;


	if ((fp = ofile (fd)) == NULL)
		return;


/*
 * proposed new locked region
 */


	u.count = size;
	u.offset = fp->rwptr;

	ip = fp->inode;

	new = NULL;

	for (l = llist; l < llist + NLOCK; l++)
		{
		if (l->file)
			{
			if (l->file->inode == ip && lockhit (l))
				{
				u.error = EBUSY;
				return;
				}
			}
			
		else
			{
			new = l;
			}
		}

	if (new == NULL)
		{
		u.error = ENFILE;	/* Lock table full. */
		return;
		}

	new->offset = u.offset;
	new->size = u.count;
	new->file = fp;
	}

/*
 * unlock system call
 * 
 *	Remove a single lock.
 *	Unlock the region in which the reference byte lies.
 */

unlock (fd)
	register int fd;
	{
	static struct file *fp;
	static struct lock *l;

	if ((fp = ofile (fd)) == NULL)
		return;

	u.offset = fp->rwptr;
	u.count = 1;

	for (l = llist; l < llist + NLOCK; l++)
		if (l->file == fp && lockhit (l))
			l->file = NULL;
	}

/*
 * Check for region intersection.
 */

lockhit (l)
	register struct lock *l;
	{
	return (u.offset + u.count) > l->offset 
		&& (l->offset + l->size) > u.offset;
	}

/*
 * lclose - clear any remaining record locks
 */

lclose (fp)
	register struct file *fp;
	{
	static struct lock *l;

	for (l = llist; l < llist + NLOCK; l++)
		if (l->file == fp)
			l->file = NULL;
	}