1 #include <u.h>
2 #include <libc.h>
3 #include <fcall.h>
4 #include <9pclient.h>
5 #include "fsimpl.h"
6 
7 vlong
8 fsseek(CFid *fid, vlong n, int whence)
9 {
10 	Dir *d;
11 
12 	switch(whence){
13 	case 0:
14 		qlock(&fid->lk);
15 		fid->offset = n;
16 		qunlock(&fid->lk);
17 		break;
18 	case 1:
19 		qlock(&fid->lk);
20 		n += fid->offset;
21 		if(n < 0){
22 			qunlock(&fid->lk);
23 			werrstr("negative offset");
24 			return -1;
25 		}
26 		fid->offset = n;
27 		qunlock(&fid->lk);
28 		break;
29 	case 2:
30 		if((d = fsdirfstat(fid)) == nil)
31 			return -1;
32 		n += d->length;
33 		if(n < 0){
34 			werrstr("negative offset");
35 			return -1;
36 		}
37 		qlock(&fid->lk);
38 		fid->offset = n;
39 		qunlock(&fid->lk);
40 		break;
41 	default:
42 		werrstr("bad whence in fsseek");
43 		return -1;
44 	}
45 	return n;
46 }