text: /****************************************************************************
   * fs/dirent/fs_opendir.c
   *
   *   Copyright (C) 2007-2009, 2011, 2013-2014, 2017-2018 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 "vfs_config.h"
  
  #include "dirent.h"
  #include "string.h"
  #include "assert.h"
  #include "errno.h"
  
  #include "stdlib.h"
  #include "fs/fs.h"
  #include "fs/dirent_fs.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++;
    inode->i_child->i_crefs++;
    dir->fd_root              = inode; /* Save the inode where we start */
    dir->u.pseudo.fd_next     = inode->i_child; /* 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.
     */
    /* 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;
    FAR struct fs_dirent_s *dir;
    FAR const char *relpath;
    int ret;
    char *fullpath;
    char *fullpath_bak;
  
    /* If we are given 'nothing' then we will interpret this as
     * request for the root inode.
     */
  
    ret = vfs_normalize_path((const char *)NULL, path, &fullpath);
    if (ret < 0)
      {
        ret = -ret;
        goto errout;
      }
    fullpath_bak = fullpath;
  
    inode_semtake();
  
    /* We don't know what to do with relative pathes */
  
    if (*fullpath != '/')
      {
        ret = ENOTDIR;
        goto errout_with_semaphore;
      }
  
    /* Find the node matching the path. */
  
    inode = inode_search((FAR const char **)&fullpath, (FAR struct inode**)NULL,
                             (FAR struct inode**)NULL, &relpath);
  
    /* Did we get an inode? */
  
    if (inode == NULL)
      {
        /* '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 *)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 */
  
    /* 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 (!*relpath && child)
      {
        /* It looks we have a valid pseudo-filesystem directory node. */
  
        open_pseudodir(inode, dir);
      }
  
  #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
  
    if (!*relpath && child == NULL)
      {
        if (inode->u.i_ops == NULL)
          {
            /* 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;
          }
      }
    else if (*relpath)
      {
        ret = ENOENT;
        goto errout_with_direntry;
      }
  
    dir->fd_status = DIRENT_MAGIC;
    inode_semgive();
    free(fullpath_bak);
    return ((DIR *)dir);
  
    /* Nasty goto's make error handling simpler */
  
  errout_with_direntry:
    free(dir);
  
  errout_with_semaphore:
    inode_semgive();
    free(fullpath_bak);
  
  errout:
    set_errno(ret);
    return NULL;
  }
  
  int do_opendir(const char *path, int oflags)
  {
    int ret;
    int fd;
    FAR struct inode *inode = NULL;
    FAR struct fs_dirent_s *dir = NULL;
    FAR const char *relpath = NULL;
    char *fullpath = NULL;
    FAR struct file *filep = NULL;
    FAR struct inode *child = NULL;
    struct inode_search_s desc;
  
    /* If we are given 'nothing' then we will interpret this as
     * request for the root inode.
     */
  
    ret = vfs_normalize_path((const char *)NULL, path, &fullpath);
    if (ret < 0)
      {
        ret = -ret;
        goto errout;
      }
  
    /* We don't know what to do with relative pathes */
  
    if (*fullpath != '/')
      {
        ret = ENOTDIR;
        goto errout_with_path;
      }
  
    /* Get an inode for this file */
  
    SETUP_SEARCH(&desc, fullpath, false);
    ret = inode_find(&desc);
    if (ret < 0)
      {
        PRINTK("ERROR: Failed to find %s\n", fullpath);
  
        /* 'path' does not exist. */
  
        ret = ENOTDIR;
        goto errout_with_path;
      }
    inode = desc.node;
    relpath = desc.relpath;
  
    /* Associate the inode with a file structure */
  
    fd = files_allocate(inode, oflags, 0, NULL, 3); /* 3: file start fd */
    if (fd < 0)
      {
        ret = EMFILE;
        goto errout_with_inode;
      }
  
    /* Get the file structure corresponding to the file descriptor. */
  
    ret = fs_getfilep(fd, &filep);
    if (ret < 0)
      {
        ret = EPERM;
  
        /* The errno value has already been set */
        goto errout_with_fd;
      }
  
    /* Perform the driver open operation.  NOTE that the open method may be
     * called many times.  The driver/mountpoint logic should handled this
     * because it may also be closed that many times.
     */
  
    ret = OK;
    filep->f_path = fullpath; /* The mem will free in close(fd); */
    filep->f_relpath = relpath;
  
    /* Allocate a type DIR -- which is little more than an inode
     * container.
     */
  
    dir = (FAR struct fs_dirent_s *)zalloc(sizeof(struct fs_dirent_s));
    if (!dir)
      {
        /* Insufficient memory to complete the operation. */
  
        ret = ENOMEM;
        goto errout_with_fd;
      }
  
    /* 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 */
  
    /* 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.
    */
  
    child = inode->i_child;
    if (!*relpath && child)
      {
        /* It looks we have a valid pseudo-filesystem directory node. */
  
        open_pseudodir(inode, dir);
      }
  
  #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
  
    if (!*relpath && child == NULL)
      {
        if (inode->u.i_ops == NULL)
          {
            /* 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;
          }
      }
    else if (*relpath)
      {
        ret = ENOENT;
        goto errout_with_direntry;
      }
  
    dir->fd_status = DIRENT_MAGIC;
    filep->f_dir = (struct fs_dirent_s *)dir;
    return fd;
  
    /* Nasty goto's make error handling simpler */
  
  errout_with_direntry:
    free(dir);
  
  errout_with_fd:
    files_release(fd);
  
  errout_with_inode:
    inode_release(inode);
  
  errout_with_path:
    free(fullpath);
  
  errout:
    set_errno(ret);
    return -1;
  }
  