1 /****************************************************************************
2 * fs/dirent/fs_seekdir.c
3 *
4 * Copyright (C) 2007, 2008, 2011, 2014 Gregory Nutt. All rights reserved.
5 * Author: Gregory Nutt <gnutt@nuttx.org>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name NuttX nor the names of its contributors may be
18 * used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
28 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
31 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
32 * POSSIBILITY OF SUCH DAMAGE.
33 *
34 ****************************************************************************/
35
36 /****************************************************************************
37 * Included Files
38 ****************************************************************************/
39
40 #include "vfs_config.h"
41 #include "sys/types.h"
42 #include "dirent.h"
43 #include "errno.h"
44 #include "fs/dirent_fs.h"
45 #include "vnode.h"
46
47 /****************************************************************************
48 * Private Functions
49 ****************************************************************************/
50 /****************************************************************************
51 * Name: seekmountptdir
52 ****************************************************************************/
53
seekmountptdir(struct fs_dirent_s * idir,off_t offset)54 static inline void seekmountptdir(struct fs_dirent_s *idir, off_t offset)
55 {
56 struct Vnode *vnode;
57 off_t pos;
58
59 /* Determine a starting point for the seek. If the seek
60 * is "forward" from the current position, then we will
61 * start at the current poisition. Otherwise, we will
62 * "rewind" to the root dir.
63 */
64
65 vnode = idir->fd_root;
66 if (offset < idir->fd_position)
67 {
68 if (vnode->vop != NULL && vnode->vop->Rewinddir != NULL)
69 {
70 /* Perform the rewinddir() operation */
71
72 vnode->vop->Rewinddir(vnode, idir);
73 pos = 0;
74 }
75 else
76 {
77 /* We can't do the seek and there is no way to return
78 * an error indication.
79 */
80
81 return;
82 }
83 }
84 else
85 {
86 pos = idir->fd_position;
87 }
88
89 /* This is a brute force approach... we will just read
90 * directory entries until we are at the desired position.
91 */
92
93 idir->read_cnt = 1;
94
95 while (pos < offset)
96 {
97 if (!vnode->vop || !vnode->vop->Readdir ||
98 vnode->vop->Readdir(vnode, idir) <= 0)
99 {
100 /* We can't read the next entry and there is no way to return
101 * an error indication.
102 */
103
104 return;
105 }
106
107 /* Increment the position on each successful read */
108
109 pos++;
110 }
111
112 /* If we get here the directory position has been successfully set */
113 idir->fd_position = pos;
114 }
115
116 /****************************************************************************
117 * Public Functions
118 ****************************************************************************/
119
120 /****************************************************************************
121 * Name: seekdir
122 *
123 * Description:
124 * The seekdir() function sets the location in the directory stream from
125 * which the next readdir() call will start. seekdir() should be used with
126 * an offset returned by telldir().
127 *
128 * Input Parameters:
129 * dirp -- An instance of type DIR created by a previous
130 * call to opendir();
131 * offset -- offset to seek to
132 *
133 * Returned Value:
134 * None
135 *
136 ****************************************************************************/
137
seekdir(DIR * dirp,long offset)138 void seekdir(DIR *dirp, long offset)
139 {
140 struct fs_dirent_s *idir = (struct fs_dirent_s *)dirp;
141
142 if (!idir || !idir->fd_root || idir->fd_status != DIRENT_MAGIC)
143 {
144 set_errno(EBADF);
145 return;
146 }
147
148 if (offset < 0)
149 {
150 set_errno(EINVAL);
151 return;
152 }
153
154 seekmountptdir(idir, offset);
155 }
156