/****************************************************************************
* fs/dirent/fs_opendir.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* 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
int ret;
/* If we are given 'nothing' then we will interpret this as
* request for the root inode.
*/
SETUP_SEARCH(&desc, path, false);
ret = inode_semtake();
if (ret < 0)
{
ret = -ret;
goto errout;
}
/* 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 */
/* Is this a node in the pseudo filesystem? Or a mountpoint? */
#ifndef CONFIG_DISABLE_MOUNTPOINT
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;
}
}
else
#endif
{
/* 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();
errout:
set_errno(ret);
return NULL;
}