/****************************************************************************
* fs/fs_seekdir.c
*
* Copyright (C) 2007, 2008, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <dirent.h>
#include <errno.h>
#include <nuttx/fs/fs.h>
#include <nuttx/fs/dirent.h>
#include "fs_internal.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: seekpseudodir
****************************************************************************/
static inline void seekpseudodir(struct fs_dirent_s *idir, off_t offset)
{
struct inode *curr;
struct inode *prev;
off_t pos;
/* Determine a starting point for the seek. If the seek
* is "forward" from the current position, then we will
* start at the current poisition. Otherwise, we will
* "rewind" to the root dir.
*/
if ( offset < idir->fd_position )
{
pos = 0;
curr = idir->fd_root;
}
else
{
pos = idir->fd_position;
curr = idir->u.pseudo.fd_next;
}
/* Traverse the peer list starting at the 'root' of the
* the list until we find the node at 'offset". If devices
* are being registered and unregistered, then this can
* be a very unpredictable operation.
*/
inode_semtake();
for (; curr && pos != offset; pos++, curr = curr->i_peer);
/* Now get the inode to vist next time that readdir() is called */
prev = idir->u.pseudo.fd_next;
idir->u.pseudo.fd_next = curr; /* The next node to visit (might be null) */
idir->fd_position = pos; /* Might be beyond the last dirent */
if (curr)
{
/* Increment the reference count on this next node */
curr->i_crefs++;
}
inode_semgive();
if (prev)
{
inode_release(prev);
}
}
/****************************************************************************
* Name: seekmountptdir
****************************************************************************/
#ifndef CONFIG_DISABLE_MOUNTPOINT
static inline void seekmountptdir(struct fs_dirent_s *idir, off_t offset)
{
struct inode *inode;
off_t pos;
/* Determine a starting point for the seek. If the seek
* is "forward" from the current position, then we will
* start at the current poisition. Otherwise, we will
* "rewind" to the root dir.
*/
inode = idir->fd_root;
if ( offset < idir->fd_position )
{
if (inode->u.i_mops && inode->u.i_mops->rewinddir)
{
/* Perform the rewinddir() operation */
inode->u.i_mops->rewinddir(inode, idir);
pos = 0;
}
else
{
/* We can't do the seek and there is no way to return
* an error indication.
*/
return;
}
}
else
{
pos = idir->fd_position;
}
/* This is a brute force approach... we will just read
* directory entries until we are at the desired position.
*/
while (pos < offset)
{
if (!inode->u.i_mops || !inode->u.i_mops->readdir ||
inode->u.i_mops->readdir(inode, idir) < 0)
{
/* We can't read the next entry and there is no way to return
* an error indication.
*/
return;
}
/* Increment the position on each successful read */
pos++;
}
/* If we get here the directory position has been successfully set */
idir->fd_position = pos;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: seekdir
*
* Description:
* The seekdir() function sets the location in the directory stream from
* which the next readdir() call will start. seekdir() should be used with
* an offset returned by telldir().
*
* Inputs:
* dirp -- An instance of type DIR created by a previous
* call to opendir();
* offset -- offset to seek to
*
* Return:
* None
*
****************************************************************************/
void seekdir(FAR DIR *dirp, off_t offset)
{
struct fs_dirent_s *idir = (struct fs_dirent_s *)dirp;
/* Sanity checks */
if (!idir || !idir->fd_root)
{
return;
}
/* The way we handle the readdir depends on the type of inode
* that we are dealing with.
*/
#ifndef CONFIG_DISABLE_MOUNTPOINT
if (INODE_IS_MOUNTPT(idir->fd_root))
{
/* The node is a file system mointpoint */
seekmountptdir(idir, offset);
}
else
#endif
{
/* The node is part of the root pseudo file system */
seekpseudodir(idir, offset);
}
}
