1 #include	"lib9.h"
2 #include	<bio.h>
3 
4 long long
5 Bseek(Biobuf *bp, long long offset, int base)
6 {
7 	vlong n, d;
8 	int bufsz;
9 
10 	switch(bp->state) {
11 	default:
12 		fprint(2, "Bseek: unknown state %d\n", bp->state);
13 		return Beof;
14 
15 	case Bracteof:
16 		bp->state = Bractive;
17 		bp->icount = 0;
18 		bp->gbuf = bp->ebuf;
19 
20 	case Bractive:
21 		n = offset;
22 		if(base == 1) {
23 			n += Boffset(bp);
24 			base = 0;
25 		}
26 
27 		/*
28 		 * try to seek within buffer
29 		 */
30 		if(base == 0) {
31 			d = n - Boffset(bp);
32 			bufsz = bp->ebuf - bp->gbuf;
33 			if(-bufsz <= d && d <= bufsz){
34 				bp->icount += d;
35 				if(d >= 0) {
36 					if(bp->icount <= 0)
37 						return n;
38 				} else {
39 					if(bp->ebuf - bp->gbuf >= -bp->icount)
40 						return n;
41 				}
42 			}
43 		}
44 
45 		/*
46 		 * reset the buffer
47 		 */
48 		n = lseek(bp->fid, n, base);
49 		bp->icount = 0;
50 		bp->gbuf = bp->ebuf;
51 		break;
52 
53 	case Bwactive:
54 		Bflush(bp);
55 		n = seek(bp->fid, offset, base);
56 		break;
57 	}
58 	bp->offset = n;
59 	return n;
60 }