#include	"dat.h"
#include	"fns.h"
#include	"error.h"

typedef struct Buffile Buffile;
struct Buffile
{
	uchar	*p;
	int	s;
	int	e;
};

enum
{
	Qdir,
	Qbuffile,
};

Dirtab bufdir[] =
{
	".",		{Qdir,0,QTDIR},	0,		DMDIR|0500,
	"new",		{Qbuffile},	0,		0660,
};

static Buffile*
buffilealloc(uchar *p, int n)
{
	Buffile *b;

	b = malloc(sizeof b[0]+n);
	b->p = (uchar*)b+sizeof b[0];
	memmove(b->p, p, n);
	b->s = 0;
	b->e = n;
	return b;
}

static Chan*
bufattach(char *spec)
{
	return devattach('β', spec);
}

static Walkqid*
bufwalk(Chan *c, Chan *nc, char **name, int nname)
{
	return devwalk(c, nc, name, nname, bufdir, nelem(bufdir), devgen);
}

static int
bufstat(Chan *c, uchar *db, int n)
{
        return devstat(c, db, n, bufdir, nelem(bufdir), devgen);
}

static Chan*
bufopen(Chan *c, int omode)
{
	return devopen(c, omode, bufdir, nelem(bufdir), devgen);
}

static void
bufclose(Chan *c)
{
	free(c->aux);
	c->aux = nil;
}

static long
bufread(Chan *c, void *va, long n, vlong off)
{
	Buffile *b;
	int have;

	if(c->qid.type == QTDIR)
		return devdirread(c, va, n, bufdir, nelem(bufdir), devgen);

	b = c->aux;
	if(b == nil)
		return 0;
	
	USED(off);
	have = b->e - b->s;
	if(have < n || n < 0)
		n = have;
	memmove(va, b->p, n);
	b->s += n;
	return n;
}

static long
bufwrite(Chan *c, void *va, long n, vlong off)
{
	if(c->qid.type == QTDIR)
		error(Eisdir);

	free(c->aux);
	c->aux = buffilealloc(va, n);
	return n;
}


Dev bufdevtab = {
	'β',
	"buf",

	devinit,
	bufattach,
	bufwalk,
	bufstat,
	bufopen,
	devcreate,
	bufclose,
	bufread,
	devbread,
	bufwrite,
	devbwrite,
	devremove,
	devwstat,
};