The Be Book - Classes And Methods - The Storage Kit

BDirectory

Derived From:	`BNode`, `BEntryList`
Mix-in Classes:	None
Declared In:	`be/storage/Directory.h`
Library:	`libbe.so`
Allocation:	–
Class Overview

Constructor and Destructor

BDirectory()

BDirectory(); BDirectory(const entry_ref* ref); BDirectory(const BEntry* entry); BDirectory(const node_ref* nref); BDirectory(const char* path);

BDirectory(const BDirectory* dir,
           const char* path);

BDirectory(const BDirectory& directory);

Creates a new BDirectory object that represents the directory as given by the arguments. See the analogous SetTo() functions for descriptions of the flavorful constructors.

The default constructor does nothing; it should be followed by a call to SetTo().
The copy constructor points the BDirectory to the same directory as is represented by the argument. The two objects have their own entry iterators.

To check to see if an initialization was successful, call InitCheck().

~BDirectory()

virtual ~BDirectory()();

Deletes the object.

Member Functions

Contains()

bool Contains(const char* path,
              int32 nodeFlags = B_ANY_NODE) const;

bool Contains(const BEntry* entry,
              int32 nodeFlags = B_ANY_NODE) const;

Returns true if path or entry is contained within this directory, or in any of its subdirectories (no matter how deep). You can use the nodeFlags argument to limit the search to a particular flavor of node:

B_FILE_NODE looks for a "plain" file.
B_DIRECTORY_NODE looks for a directory.
B_SYMLINK_NODE looks for a symbolic link.
B_ANY_NODE (the default) doesn't discriminate between flavors.

CreateFile(), CreateDirectory(), CreateSymLink()

status_t CreateFile(const char* path,
                    BFile* file,
                    bool failIfExists = false);

status_t CreateDirectory(const char* path,
                         BDirectory* dir);

status_t CreateSymLink(const char* path,
                       const char* linkToPath,
                       BSymLink* link);

These functions create a new file, directory, or symbolic link. The new node is located at path. If path is relative, it's reckoned off of the directory represented by this BDirectory; if it's absolute, the path of this BDirectory is ignored.

CreateFile() fails if the file already exists and failIfExists is true. If the flag is false (and the file exists), the old file is clobbered and a new one is created. If successful, the BFile argument that you pass in is opened on the new file in B_READ_WRITE mode.
CreateDirectory() and CreateSymLink() fail if path already exists—you can't clobber an existing directory or link.
The linkToPath argument (CreateSymLink()) is the path that the new symbolic link will be linked to.

The object argument (the BDirectory, BFile, or BSymLink) may be NULL. If the function fails, the object argument, if non-NULL, is Unset().

RETURN CODES

B_OK.: Success.
B_BAD_VALUE.: Illegal path, file, dir, or link specified; may be NULL. path may be empty.
B_BUSY.: A busy node could not be accessed.
B_ENTRY_NOT_FOUND.: The specified path does not exist or is an empty string.
B_FILE_ERROR.: A file system error prevented the operation.
B_FILE_EXISTS.: The file specified by path already exists.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_NAME_TOO_LONG.: The path specified is too long.
B_NO_MEMORY.: Insufficient memory to perform the operation.
B_NO_MORE_FDS.: All file descriptors are in use (too many open files).
B_IS_A_DIRECTORY.: Can't replace a directory with a file.
B_NOT_A_DIRECTORY.: A component of the path is not a directory.
B_NOT_ALLOWED.: The volume is read-only.
B_PERMISSION_DENIED.: Create access is denied in the specified path.
E2BIG.: linkToPath is too long (CreateSymLink() only).

FindEntry()

status_t FindEntry(const char* path,
                   BEntry* entry,
                   bool traverse = false) const;

Finds the entry with the given name, and sets the second argument to refer to that entry.

path must be a relative pathname. It's reckoned off of the BDirectory's directory.
You are allowed to look for "." and "..". The former represents this directory's entry. The latter refers to this directory's parent.
The entry argument must be allocated before it's passed in (it needn't be initialized).
The traverse applies to symbolic links: If the flag is true, the link is traversed. If it's false, you get the BEntry that points to the link itself.

If path isn't found, the second argument is automatically Unset(). To find out why the lookup failed, invoke InitCheck() on the entry argument:

BEntry entry;
status_t err;

if (dir.FindEntry("aFile", &entry) != B_OK) {
   err = entry.InitCheck();
}

The direct return value is also informative, but it may not be as precise as the InitCheck() value.

RETURN CODES

B_OK.: Success.
B_BAD_VALUE.: Invalid path specified; it may be NULL or empty.
B_ENTRY_NOT_FOUND.: The specified path does not exist.
B_NAME_TOO_LONG.: The path specified is too long.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_NO_MEMORY.: Insufficient memory to perform the operation.
B_FILE_ERROR.: An invalid file prevented the operation.

GetEntry()

status_t GetEntry(BEntry* entry) const;

Initializes entry to represent this BDirectory. If the initialization fails, entry is Unset().

RETURN CODES

B_OK.: Success.
B_NAME_TOO_LONG.: The path specified by entry is too long.
B_ENTRY_NOT_FOUND.: The specified path does not exist.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_BAD_VALUE.: entry is uninitialized.
B_NO_MEMORY.: Insufficient memory to perform the operation.
B_BUSY.: A busy node could not be accessed.
B_FILE_ERROR.: An invalid file prevented the operation.
B_NO_MORE_FDS.: All file descriptors are in use (too many open files).
B_NOT_A_DIRECTORY.: The path includes non-directory entries.

GetNextEntry(), GetNextRef(), GetNextDirents(), CountEntries(),Rewind()

virtual status_t GetNextEntry(BEntry* entry,
                              bool traverse = false);

virtual status_t GetNextRef(entry_ref* ref);

virtual int32 GetNextDirents(dirent* buf,
                             size_t bufsize,
                             int32 count = INT_MAX);

virtual int32 CountEntries();virtual status_t Rewind();

The three GetNext…() functions retrieve the "next" entry that lives in the BDirectory and returns it as a BEntry, entry_ref, or dirent structure.

GetNextEntry() returns the entry as a BEntry object. If traverse is true and the entry is a symbolic link, the link is traversed. In other words, entry could end up being in a different directory than the one referred to by this. When all entries have been visited, the function returns B_ENTRY_NOT_FOUND. The entry argument must be allocated before it's passed in.
GetNextRef() return the next entry in ref. Since an entry_ref doesn't supply enough information to determine if the entry is a link, there's no question of traversal: The entry_ref points to exactly the next entry. When all entries have been visited, the function returns B_ENTRY_NOT_FOUND. The ref argument must be allocated before it's passed in.
GetNextDirents() returns some number of dirent structures, either as many as can be stuffed into buf (where bufsize gives the size of buf), or count structures, whichever is smaller. The function returns the number of structures that were stuffed into buf; when all entries have been visited, it returns 0.

Warning

Currently, GetNextDirents() only reads one dirent at a time, no matter how many you ask for.

GetNextEntry() and GetNextRef() are reasonably clear; the dirent version deserves more explanation. You'll find this explanation (and an example) in the BEntryList class. Also, keep in mind that the set of candidate entries is different for the dirent version: GetNextDirents() finds all entries, including the entries for "." and "..". The other two versions skip these entries.

When you're done reading the BDirectory's entries, you can rewind the object's entry iterator by calling Rewind().

CountEntries() returns the number of entries (not counting "." and "..") in the directory.

Warning

Never call CountEntries() while you're iterating through the directory. CountEntries() does a rewind, iterates through the entries, and then rewinds again.

RETURN CODES

B_OK.: Success.
B_FILE_ERROR.: BDirectory object has not been properly initialized.
B_NOT_A_DIRECTORY.: The directory is invalid.
B_NAME_TOO_LONG.: The dirent's name is too long.
B_ENTRY_NOT_FOUND.: End of directory reached.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_BAD_VALUE.: Invalid input specified, or BDirectory object has not been properly initialized.
B_NO_MEMORY.: Insufficient memory to perform the operation.

GetStatFor()

status_t GetStatFor(const char* path,
                    stat* st) const;

Gets the stat structure for the entry designated by path. path may be either absolute or relative; if it's relative, it's reckoned off of the BDirectory's directory. This is, primarily, a convenience function; but it's also provided for efficiency.

RETURN CODES

B_OK.: Success.
B_FILE_ERROR.: An invalid file prevented the operation.
B_NAME_TOO_LONG.: The path specified is too long.
B_ENTRY_NOT_FOUND.: The specified path does not exist.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_BAD_VALUE.: Invalid input specified; the path may be NULL or empty.
B_NO_MEMORY.: Insufficient memory to perform the operation.

IsRootDirectory()

bool IsRootDirectory() const;

Returns true if this BDirectory represents a root directory. A root directory is the directory that's at the root of a volume's file hierarchy. Every volume has exactly one root directory; all other files in the volume's hierarchy descend from the root directory.

SetTo(), Unset()

status_t SetTo(const entry_ref* ref); status_t SetTo(const node_ref* nref); status_t SetTo(const BEntry* entry); status_t SetTo(const char* path);

status_t SetTo(const BDirectory* directory,
               const char* path);

void Unset();

Closes the BDirectory's current directory (if any), and initializes the object to open the directory as given by the arguments.

In the path version, path can be absolute or relative, and can contain "." and ".." elements. If path is relative, it's reckoned off of the current working directory.
In the dir/path version, path must be relative. It's reckoned off of the directory given by dir.

If the specification results in a symbolic link that resolves to a directory, then the linked-to directory is opened. If the specification is (or resolves to) a regular file, the initialization fails.

RETURN CODES

B_OK.: Success.
B_NAME_TOO_LONG.: The path specified is too long.
B_ENTRY_NOT_FOUND.: The directory does not exist.
B_LINK_LIMIT.: A cyclic loop has been detected in the file system.
B_BAD_VALUE.: Invalid input specified.
B_NO_MEMORY.: Insufficient memory to perform the operation.
B_BUSY.: A busy node could not be accessed.
B_FILE_ERROR.: An invalid file prevented the operation.
B_NO_MORE_FDS.: All file descriptors are in use (too many open files).

Operators

= (assignment)

BDirectory& operator=(const BDirectory& directory);

In the expression

BDirectory a = b;

BDirectory a is initialized to refer to the same directory as b. To gauge the success of the assignment, you should call InitCheck() immediately afterwards. Assigning a BDirectory to itself is safe.

Assigning from an uninitialized BDirectory is "successful": The assigned-to BDirectory will also be uninitialized (B_NO_INIT).

C Functions

create_directory()

status_t create_directory(const char* path,
                          mode_t mode);

Creates all missing directories along the path specified by path.

The pathname can be absolute or relative. If it's relative, the path is reckoned of the current working directory. If any symlinks are found in the existing portion of the path, they're traversed.
path can contain ".", but it may not contain "..".
mode is the permissions setting (typically expressed as an octal number) that's assigned to all directories that are created. To set the directories to be readable, writable, and "enterable" by all (for example), you would set the mode to 0777.

RETURN CODES

B_OK.: path now fully exists (or did in the first place).
B_BAD_VALUE.: path is NULL, is empty, or contains "..".
B_NOT_ALLOWED.: Read-only volume.
B_NO_MEMORY.: Insufficient memory to perform the operation.

find_directory()

Declared in: be/storage/FindDirectory.h

status_t find_directory(directory_which which,
                        dev_t volume,
                        bool create_it,
                        char* path_string,
                        int32 length);

status_t find_directory(directory_which which,
                        BPath* path_obj,
                        bool create_it = false,
                        BVolume volume = NULL);

Note

The first version of this function can be used in either C or C++ code. The second version is for C++ code only.

Finds the path to the directory symbolized by which and copies it into path_string, or uses it to initialize path_obj.

The create_it argument tells the function to create the directory if it doesn't already exist.
volume identifies the volume (as a dev_t identifier or BVolume object) on which you want to look. The C++ default (NULL) means to look in the boot volume.
The length argument (first version only) gives the length of path.

The directory_which constants are described in the "Constants" section.

RETURN CODES

B_OK.: The directory was found.
Other codes.: The directory wasn't found or couldn't be created.