-
Notifications
You must be signed in to change notification settings - Fork 1
/
bsseek.c
50 lines (47 loc) · 1015 Bytes
/
bsseek.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
/*
* This file is part of "jelio".
* jelio is an input/output library that replaces the standard C IO library.
*
* Copyright: Jens Låås, SLU 2004
* Copyright license: According to GPL, see file COPYING in this directory.
*
*/
#include "jelio.h"
#include "jelio_internal.h"
#include <stdlib.h>
off_t bsseek(struct jelbs *s, off_t offset, int whence)
{
switch(whence)
{
case SEEK_SET:
s->bytepos = offset / 8;
s->bitpos = 7-(offset % 7);
break;
case SEEK_CUR:
s->bytepos += offset / 8;
s->bitpos -= (offset % 7);
break;
case SEEK_END:
s->bytepos = s->size + offset / 8;
s->bitpos = 0-(offset % 7);
break;
default:
return -1;
}
if(s->bitpos < 0)
{
s->bitpos += 8;
s->bytepos++;
}
if(s->bitpos > 7)
{
s->bitpos -= 8;
s->bytepos--;
}
if(s->bytepos < 0 || s->bytepos >= s->size)
{
s->eof=1;
s->bytepos=0;
}
return (s->bytepos << 3) + (7-s->bitpos);
}