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Diffstat (limited to 'nuttx/fs/fs_seekdir.c')
| -rw-r--r-- | nuttx/fs/fs_seekdir.c | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/nuttx/fs/fs_seekdir.c b/nuttx/fs/fs_seekdir.c new file mode 100644 index 000000000..ec530c67d --- /dev/null +++ b/nuttx/fs/fs_seekdir.c @@ -0,0 +1,230 @@ +/**************************************************************************** + * 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: seekpsuedodir + ****************************************************************************/ + +static inline void seekpsuedodir(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.psuedo.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.psuedo.fd_next; + idir->u.psuedo.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 psuedo file system */ + + seekpsuedodir(idir, offset); + } +} |