#include	"u.h"
#include	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"../port/error.h"

extern Rootdata rootdata[];
extern Dirtab roottab[];
extern int	rootmaxq;

static Chan*
rootattach(char *spec)
{
	int i;

	for (i = 0; i < rootmaxq; i++)
		if (rootdata[i].sizep)
			rootdata[i].size = roottab[i].length = *rootdata[i].sizep;

	return devattach('/', spec);
}

static int
rootgen(Chan *c, Dirtab *d, int nd, int s, Dir *dp)
{
	int p, i;
	char *name;

	if(s == DEVDOTDOT){
		p = rootdata[c->qid.path & ~CHDIR].dotdot;
		c->qid.path = p | CHDIR;
		name = "#/";
		if(p != 0){
			for(i = 0; i < rootmaxq; i++)
				if(roottab[i].qid.path == c->qid.path){
					name = roottab[i].name;
					break;
				}
		}
		devdir(c, c->qid, name, 0, eve, 0555, dp);
		return 1;
	}
	return devgen(c, d, nd, s, dp);
}

static int	 
rootwalk(Chan *c, char *name)
{
	ulong p;

	p = c->qid.path & ~CHDIR;
	if(c->qid.path & CHDIR)
		return devwalk(c, name, rootdata[p].ptr, rootdata[p].size, rootgen);
	return 0;
}

static void
rootstat(Chan *c, char *dp)
{
	int p;

	p = rootdata[c->qid.path & ~CHDIR].dotdot;
	devstat(c, dp, rootdata[p].ptr, rootdata[p].size, rootgen);
}

static Chan*
rootopen(Chan *c, int omode)
{
	int p;

	p = rootdata[c->qid.path & ~CHDIR].dotdot;
	return devopen(c, omode, rootdata[p].ptr, rootdata[p].size, rootgen);
}

/*
 * sysremove() knows this is a nop
 */
static void	 
rootclose(Chan*)
{
}

static long	 
rootread(Chan *c, void *buf, long n, ulong offset)
{
	ulong p;
	ulong len;
	uchar *data;

	p = c->qid.path & ~CHDIR;
	if(c->qid.path & CHDIR)
		return devdirread(c, buf, n, rootdata[p].ptr, rootdata[p].size, rootgen);
	data = rootdata[p].ptr;
	len = rootdata[p].size;
	if(offset >= len)
		return 0;
	if(offset+n > len)
		n = len - offset;
	memmove(buf, data+offset, n);
	return n;
}

static long	 
rootwrite(Chan*, void*, long, ulong)
{
	error(Eperm);
	return 0;
}

Dev rootdevtab = {
	'/',
	"root",

	devreset,
	devinit,
	rootattach,
	devdetach,
	devclone,
	rootwalk,
	rootstat,
	rootopen,
	devcreate,
	rootclose,
	rootread,
	devbread,
	rootwrite,
	devbwrite,
	devremove,
	devwstat,
};