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
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
|
/* $OpenBSD: seekdir.c,v 1.12 2014/03/10 07:54:14 schwarze Exp $ */
/*
* Copyright (c) 2013 Ingo Schwarze <schwarze@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <dirent.h>
#include <unistd.h>
#include "thread_private.h"
#include "telldir.h"
/*
* Seek to an entry in a directory.
* Only values returned by "telldir" should be passed to seekdir.
*/
void
seekdir(DIR *dirp, long loc)
{
struct dirent *dp;
/*
* First check whether the directory entry to seek for
* is still buffered in the directory structure in memory.
*/
_MUTEX_LOCK(&dirp->dd_lock);
if (dirp->dd_size && dirp->dd_bufpos == loc) {
dirp->dd_loc = 0;
dirp->dd_curpos = loc;
_MUTEX_UNLOCK(&dirp->dd_lock);
return;
}
for (dirp->dd_loc = 0;
dirp->dd_loc < dirp->dd_size;
dirp->dd_loc += dp->d_reclen) {
dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc);
if (dp->d_off != loc)
continue;
/*
* Entry found in the buffer, use it. If readdir(3)
* follows, this will save us a getdents(2) syscall.
* Note that d_off is the offset of the _next_ entry,
* so advance dd_loc.
*/
dirp->dd_loc += dp->d_reclen;
dirp->dd_curpos = loc;
_MUTEX_UNLOCK(&dirp->dd_lock);
return;
}
/*
* The entry is not in the buffer, prepare a call to getdents(2).
* In particular, invalidate dd_loc.
*/
dirp->dd_loc = dirp->dd_size;
dirp->dd_bufpos = dirp->dd_curpos = lseek(dirp->dd_fd, loc, SEEK_SET);
_MUTEX_UNLOCK(&dirp->dd_lock);
}
|
