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incubator-nuttx/fs/dirent/fs_opendir.c

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/****************************************************************************
* fs/dirent/fs_opendir.c
*
* Copyright (C) 2007-2009, 2011, 2013-2014, 2017 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 <stdbool.h>
#include <string.h>
#include <dirent.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/fs/dirent.h>
#include "inode/inode.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: open_mountpoint
*
* Description:
* Handle the case where the inode to be opened is within a mountpoint.
*
* Input Parameters:
* inode -- the inode of the mountpoint to open
* relpath -- the relative path within the mountpoint to open
* dir -- the dirent structure to be initialized
*
* Returned Value:
* On success, OK is returned; Otherwise, a positive errno is returned.
*
****************************************************************************/
#ifndef CONFIG_DISABLE_MOUNTPOINT
static inline int open_mountpoint(FAR struct inode *inode,
FAR const char *relpath,
FAR struct fs_dirent_s *dir)
{
int ret;
/* The inode itself as the 'root' of mounted volume. The actually
* directory is at relpath into the* mounted filesystem.
*
* Verify that the mountpoint inode supports the opendir() method
*/
if (!inode->u.i_mops || !inode->u.i_mops->opendir)
{
return ENOSYS;
}
/* Take reference to the mountpoint inode. Note that we do not use
* inode_addref() because we already hold the tree semaphore.
*/
inode->i_crefs++;
/* Perform the opendir() operation */
ret = inode->u.i_mops->opendir(inode, relpath, dir);
if (ret < 0)
{
/* We now need to back off our reference to the inode. We can't
* call inode_release() to do that unless we release the tree
* semaphore. The following should be safe because: (1) after the
* reference count was incremented above it should be >=1 so it should
* not decrement below zero, and (2) we hold the tree semaphore so no
* other thread should be able to change the reference count.
*/
inode->i_crefs--;
DEBUGASSERT(inode->i_crefs >= 0);
/* Negate the error value so that it can be used to set errno */
return -ret;
}
return OK;
}
#endif
/****************************************************************************
* Name: open_pseudodir
*
* Description:
* Handle the case where the inode to be opened is within the top-level
* pseudo-file system.
*
* Input Parameters:
* inode -- the inode of the mountpoint to open
* dir -- the dirent structure to be initialized
*
* Returned Value:
* None
*
****************************************************************************/
static void open_pseudodir(FAR struct inode *inode, FAR struct fs_dirent_s *dir)
{
/* We have a valid pseudo-filesystem node. Take two references on the
* inode -- one for the parent (fd_root) and one for the child (fd_next).
* Note that we do not call inode_addref because we are holding the tree
* semaphore and that would result in deadlock.
*/
inode->i_crefs += 2;
dir->fd_root = inode; /* Save the inode where we start */
dir->u.pseudo.fd_next = inode; /* This is the next node to use for readdir() */
/* Flag the inode as belonging to the pseudo-filesystem */
#ifndef CONFIG_DISABLE_MOUNTPOINT
DIRENT_SETPSEUDONODE(dir->fd_flags);
#endif
}
/****************************************************************************
* Name: open_emptydir
*
* Description:
* Handle the case where the inode to be opened is an empty, directory node
* within the top-level pseudo-file system. That is, it has no operations
* and, therefore, it must be a directory node. But is has no children
* to be enumerated either.
*
* Input Parameters:
* dir -- the dirent structure to be initialized
*
* Returned Value:
* None
*
****************************************************************************/
static inline void open_emptydir(FAR struct fs_dirent_s *dir)
{
/* We have a valid, but empty pseudo-filesystem node. fd_next is NULL
* meaning that we are already at the end of the list of its children.
* fd_root is NULL so that if the directory is rewound, it will still be
* at the end of the list.
*/
#if 0 /* Already nullified by kumm_zalloc */
dir->fd_root = NULL; /* Save the inode where we start */
dir->u.pseudo.fd_next = NULL; /* We are at the end of the list */
#endif
/* Flag the inode as belonging to the pseudo-filesystem */
#ifndef CONFIG_DISABLE_MOUNTPOINT
DIRENT_SETPSEUDONODE(dir->fd_flags);
#endif
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: opendir
*
* Description:
* The opendir() function opens a directory stream corresponding to the
* directory name, and returns a pointer to the directory stream. The
* stream is positioned at the first entry in the directory.
*
* Input Parameters:
* path -- the directory to open
*
* Returned Value:
* The opendir() function returns a pointer to the directory stream. On
* error, NULL is returned, and errno is set appropriately.
*
* EACCES - Permission denied.
* EMFILE - Too many file descriptors in use by process.
* ENFILE - Too many files are currently open in the
* system.
* ENOENT - Directory does not exist, or name is an empty
* string.
* ENOMEM - Insufficient memory to complete the operation.
* ENOTDIR - 'path' is not a directory.
*
****************************************************************************/
FAR DIR *opendir(FAR const char *path)
{
FAR struct inode *inode = NULL;
FAR struct fs_dirent_s *dir;
struct inode_search_s desc;
#ifndef CONFIG_DISABLE_MOUNTPOINT
FAR const char *relpath = NULL;
#endif
bool isroot = false;
int ret;
/* If we are given 'nothing' then we will interpret this as
* request for the root inode.
*/
SETUP_SEARCH(&desc, path, false);
inode_semtake();
if (path == NULL || *path == '\0' || strcmp(path, "/") == 0)
{
inode = g_root_inode;
isroot = true;
}
else
{
/* We don't know what to do with relative pathes */
if (*path != '/')
{
ret = -ENOTDIR;
goto errout_with_semaphore;
}
/* Find the node matching the path. */
ret = inode_search(&desc);
if (ret >= 0)
{
inode = desc.node;
DEBUGASSERT(inode != NULL);
#ifndef CONFIG_DISABLE_MOUNTPOINT
relpath = desc.relpath;
#endif
}
}
/* Did we get an inode? */
if (inode == NULL)
{
/* Inode for 'path' does not exist. */
ret = ENOTDIR;
goto errout_with_semaphore;
}
/* Allocate a type DIR -- which is little more than an inode
* container.
*/
dir = (FAR struct fs_dirent_s *)kumm_zalloc(sizeof(struct fs_dirent_s));
if (!dir)
{
/* Insufficient memory to complete the operation. */
ret = ENOMEM;
goto errout_with_semaphore;
}
/* Populate the DIR structure and return it to the caller. The way that
* we do this depends on whenever this is a "normal" pseudo-file-system
* inode or a file system mountpoint.
*/
dir->fd_position = 0; /* This is the position in the read stream */
/* First, handle the special case of the root inode. This must be
* special-cased here because the root inode might ALSO be a mountpoint.
*/
if (isroot)
{
/* Whatever payload the root inode carries, the root inode is always
* a directory inode in the pseudo-file system
*/
open_pseudodir(inode, dir);
}
/* Is this a node in the pseudo filesystem? Or a mountpoint? If the node
* is the root (isroot == TRUE), then this is a special case.
*/
#ifndef CONFIG_DISABLE_MOUNTPOINT
else if (INODE_IS_MOUNTPT(inode))
{
/* Yes, the node is a file system mountpoint */
dir->fd_root = inode; /* Save the inode where we start */
/* Open the directory at the relative path */
ret = open_mountpoint(inode, relpath, dir);
if (ret != OK)
{
goto errout_with_direntry;
}
}
#endif
else
{
/* The node is part of the root pseudo file system. Does the inode
* have a child? If so that the child would be the 'root' of a list
* of nodes under the directory.
*/
FAR struct inode *child = inode->i_child;
if (child != NULL)
{
/* It looks we have a valid pseudo-filesystem directory node. */
open_pseudodir(child, dir);
}
else if (!inode->u.i_ops)
{
/* This is a dangling node with no children and no operations. Set
* up to enumerate an empty directory.
*/
open_emptydir(dir);
}
else
{
ret = ENOTDIR;
goto errout_with_direntry;
}
}
RELEASE_SEARCH(&desc);
inode_semgive();
return ((FAR DIR *)dir);
/* Nasty goto's make error handling simpler */
errout_with_direntry:
kumm_free(dir);
errout_with_semaphore:
RELEASE_SEARCH(&desc);
inode_semgive();
set_errno(ret);
return NULL;
}
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