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# QFileEngine Class Reference

The QFileEngine class provides an abstraction for accessing the filesystem. More...

    #include <QFileEngine>

Note: All the functions in this class are reentrant.

- List of all members, including inherited members

### Public Types

- enum FileInfo { ReadOwnerPerm, WriteOwnerPerm, ExeOwnerPerm, ReadUserPerm, WriteUserPerm, ..., LocalDiskFlag }
- enum FileName { DefaultName, BaseName, PathName, AbsoluteName, AbsolutePathName, ..., CanonicalPathName }
- enum FileOwner { OwnerUser, OwnerGroup }
- enum FileTime { CreationTime, ModificationTime, AccessTime }
- enum Type { File, Resource, User, MaxUser }

### Public Functions

- virtual ~QFileEngine ()
- virtual QIODevice::Offset at () const = 0
- virtual bool caseSensitive () const = 0
- virtual bool chmod ( uint perms ) = 0
- virtual bool close () = 0
- virtual QStringList entryList ( int filterSpec, const QStringList & filters ) const = 0
- virtual QIODevice::Status errorStatus () const
- virtual QString errorString () const
- virtual uint fileFlags ( uint type = FileInfoAll ) const = 0
- virtual QString fileName ( FileName file = DefaultName ) const = 0
- virtual QDateTime fileTime ( FileTime time ) const = 0
- virtual void flush () = 0
- virtual bool isRelativePath () const = 0
- virtual bool isSequential () const = 0
- virtual bool link ( const QString & newName ) = 0
- virtual uchar * map ( Q_LONGLONG offset, Q_LONGLONG size )
- virtual bool mkdir ( const QString & dirName, QDir::Recursion recurse ) const = 0
- virtual bool open ( int mode ) = 0
- virtual QString owner ( FileOwner owner ) const = 0
- virtual uint ownerId ( FileOwner owner ) const = 0
- virtual Q_LONGLONG read ( char * data, Q_LONGLONG maxSize ) = 0
- virtual bool remove () = 0
- virtual bool rename ( const QString & newName ) = 0
- virtual bool rmdir ( const QString & dirName, QDir::Recursion recurse ) const = 0
- virtual bool seek ( QIODevice::Offset offset ) = 0
- virtual void setFileName ( const QString & file ) = 0
- virtual bool setSize ( QIODevice::Offset size ) = 0
- virtual QIODevice::Offset size () const = 0
- virtual Type type () const = 0
- virtual void unmap ( uchar * data )
- virtual Q_LONGLONG write ( const char * data, Q_LONGLONG size ) = 0

### Static Public Members

- QFileEngine * createFileEngine ( const QString & file )

### Protected Functions

- QFileEngine ()

## Detailed Description

The QFileEngine class provides an abstraction for accessing the filesystem.

The QDir, QFile, and QFileInfo classes all make use of a QFileEngine internally. If you create your own QFileEngine subclass (and register it with Qt by creating a QFileEngineHandler subclass), your file engine will be used when the path is one that your file engine handles.

A QFileEngine refers to one file or one directory. If the referent is a file the setFileName(), rename(), and remove() functions are applicable. If the referent is a directory the mkdir(), rmdir(), and entryList() functions are applicable. In all cases the caseSensitive(), isRelativePath(), fileFlags(), ownerId(), owner(), and fileTime() functions are applicable.

A QFileEngine subclass can be created to do syncronous network I/O based file system operations, local file system operations, or to operate as a resource system to access file based resources.

See also QFileEngineHandler and setFileName().

## Member Type Documentation

### enum QFileEngine::FileInfo

The permissions and types of a file, suitable for OR'ing together.

`QFileEngine::ReadOwnerPerm` | The owner of the file has permission to read it.
`QFileEngine::WriteOwnerPerm` | The owner of the file has permission to write to it.
`QFileEngine::ExeOwnerPerm` | The owner of the file has permission to execute it.
`QFileEngine::ReadUserPerm` | The current user has permission to read the file.
`QFileEngine::WriteUserPerm` | The current user has permission to write to the file.
`QFileEngine::ExeUserPerm` | The current user has permission to execute the file.
`QFileEngine::ReadGroupPerm` | Members of the current user's group have permission to read the file.
`QFileEngine::WriteGroupPerm` | Members of the current user's group have permission to write to the file.
`QFileEngine::ExeGroupPerm` | Members of the current user's group have permission to execute the file.
`QFileEngine::ReadOtherPerm` | All users have permission to read the file.
`QFileEngine::WriteOtherPerm` | All users have permission to write to the file.
`QFileEngine::ExeOtherPerm` | All users have permission to execute the file.
`QFileEngine::LinkType` | The file is a link to another file (or link) in the file system (i.e. not a file or directory).
`QFileEngine::FileType` | The file is a regular file to the file system (i.e. not a link or directory)
`QFileEngine::DirectoryType` | The file is a directory in the file system (i.e. not a link or file).
`QFileEngine::HiddenFlag` | The file is hidden.
`QFileEngine::ExistsFlag` | The file actually exists in the file system.
`QFileEngine::RootFlag` | The file or the file pointed to is the root of the filesystem.
`QFileEngine::LocalDiskFlag` | The file resides on the local disk and can be passed to standard file functions.

See also fileFlags() and setFileName().

### enum QFileEngine::FileName

These values are used to request a file name in a particular format.

`QFileEngine::DefaultName` | The same filename that was passed to the QFileEngine.
`QFileEngine::BaseName` | The name of the file excluding the path.
`QFileEngine::PathName` | The path to the file excluding the base name.
`QFileEngine::AbsoluteName` | The absolute path to the file (including the base name).
`QFileEngine::AbsolutePathName` | The absolute path to the file (excluding the base name).
`QFileEngine::LinkName` | The full file name of the file that this file is a link to. (This will be empty if this file is not a link.)
`QFileEngine::CanonicalName` | Often very similar to LinkName. Will return the true path to the file.
`QFileEngine::CanonicalPathName` | Same as CanonicalName, excluding the base name.

See also fileName() and setFileName().

### enum QFileEngine::FileOwner

`QFileEngine::OwnerUser` | The user who owns the file.
`QFileEngine::OwnerGroup` | The group who owns the file.

See also owner(), ownerId(), and setFileName().

### enum QFileEngine::FileTime

These are used by the fileTime() function.

`QFileEngine::CreationTime` | When the file was created.
`QFileEngine::ModificationTime` | When the file was most recently modified.
`QFileEngine::AccessTime` | When the file was most recently accessed (e.g. read or written to).

See also setFileName().

### enum QFileEngine::Type

`QFileEngine::File` | The file is an actual file on the file system.
`QFileEngine::Resource` | The file is a Qt resource.
`QFileEngine::User` | The first value to be used for custom engine types.
`QFileEngine::MaxUser` | The last value to be used for custom engine types.

See also type().

## Member Function Documentation

### QFileEngine::QFileEngine () `[protected]`

Constructs a new QFileEngine that does not refer to any file or directory.

See also setFileName().

### QFileEngine::~QFileEngine () `[virtual]`

Destroys the QFileEngine.

### QIODevice::Offset QFileEngine::at () const `[pure virtual]`

Returns the current file position.

This is the position of the data read/write head of the file.

### bool QFileEngine::caseSensitive () const `[pure virtual]`

Should return true if the underlying file system is case-sensitive; otherwise return false.

This virtual function must be reimplemented by all subclasses.

### bool QFileEngine::chmod ( uint perms ) `[pure virtual]`

Requests that the file's permissions be set to perms. The argument perms will be set to the OR-ed together combination of QFileEngine::FileInfo, with only the QFileEngine::PermsMask being honored. If the operations succceeds return true; otherwise return false;

This virtual function must be reimplemented by all subclasses.

See also size().

### bool QFileEngine::close () `[pure virtual]`

Closes the file.

### QFileEngine * QFileEngine::createFileEngine ( const QString & file ) `[static]`

Creates a new QFileEngine instance for the given file. This function will always return a valid QFileEngine. The default file engine that is created if no custom file engine handles files of file's path is one that operates on the local file system.

### QStringList QFileEngine::entryList ( int filterSpec, const QStringList & filters ) const `[pure virtual]`

Requests that a list of all the files matching the filters list based on the filterSpec in the file engine's directory are returned.

Should return an empty list if the file engine refers to a file rather than a directory, or if the directory is unreadable or does not exist or if nothing matches the specifications.

This virtual function must be reimplemented by all subclasses.

See also setFileName().

### QIODevice::Status QFileEngine::errorStatus () const `[virtual]`

Returns the QIODevice::Status that resulted from the last failed operation. If QIOevice::UnspecifiedError is returned, QIODevice will use its own idea of the error status.

See also QIODevice::Status and errorString.

### QString QFileEngine::errorString () const `[virtual]`

Returns the human-readable message appropriate to the current error reported by errorStatus(). If no suitable string is available, an empty string is returned.

See also errorStatus().

### uint QFileEngine::fileFlags ( uint type = FileInfoAll ) const `[pure virtual]`

This function should return the set of OR'd `QFileEngine::FileInfo` members that are true for the file engine's file, and that are in the type's OR'd members.

In your reimplementation you can use the type argument as an optimization hint and only return the OR'd set of members that are true and that match those in type; in other words you can ignore any members not mentioned in type, thus avoiding some potentially expensive lookups or system calls.

This virtual function must be reimplemented by all subclasses.

See also setFileName() and FileInfo.

### QString QFileEngine::fileName ( FileName file = DefaultName ) const `[pure virtual]`

Return the file engine's current file name in the format specified by file.

If you don't handle some `FileName` possibilities, return the file name set in setFileName() when an unhandled format is requested.

This virtual function must be reimplemented by all subclasses.

See also setFileName() and FileName.

### QDateTime QFileEngine::fileTime ( FileTime time ) const `[pure virtual]`

If time is `CreationTime`, return when the file was created. If time is `ModificationTime`, return when the file was most recently modified. If time is `AccessTime`, return when the file was most recently accessed (e.g. read or written). If the time cannot be determined return QDateTime() (an invalid date time).

This virtual function must be reimplemented by all subclasses.

See also setFileName(), QDateTime, QDateTime::isValid(), and FileTime.

### void QFileEngine::flush () `[pure virtual]`

Flushes the open file.

### bool QFileEngine::isRelativePath () const `[pure virtual]`

Return true if the file referred to by this file engine has a relative path; otherwise return false.

This virtual function must be reimplemented by all subclasses.

See also setFileName().

### bool QFileEngine::isSequential () const `[pure virtual]`

Returns true if the file is a sequential access device; returns false if the file is a direct access device.

Operations involving size() and seek(int) are not valid on sequential devices.

### bool QFileEngine::link ( const QString & newName ) `[pure virtual]`

### uchar * QFileEngine::map ( Q_LONGLONG offset, Q_LONGLONG size ) `[virtual]`

Maps the file contents from offset for the given number of bytes size, returning a pointer to the contents. If this fails, 0 is returned.

The default implementation falls back to block reading/writing if this function returns 0.

See also unmap().

### bool QFileEngine::mkdir ( const QString & dirName, QDir::Recursion recurse ) const `[pure virtual]`

Requests that the directory dirName be created. If recurse is `QDir::Recursive` then any sub-directories in dirName that don't exist must be created. If recurse is `QDir::NonRecursive` then any sub-directories in dirName must already exist for the function to succeed. If the operation succeeds return true; otherwise return false.

This virtual function must be reimplemented by all subclasses.

See also setFileName(), rmdir(), and isRelativePath().

### bool QFileEngine::open ( int mode ) `[pure virtual]`

Opens the file in the specified mode. Returns true if the file was successfully opened; otherwise returns false.

The mode is an OR combination of QIODevice::OpenMode and QIODevice::HandlingMode values.

### QString QFileEngine::owner ( FileOwner owner ) const `[pure virtual]`

If owner is `OwnerUser` return the name of the user who owns the file. If owner is `OwnerGroup` return the name of the group that own the file. If you can't determine the owner return QString().

This virtual function must be reimplemented by all subclasses.

See also ownerId(), setFileName(), and FileOwner.

### uint QFileEngine::ownerId ( FileOwner owner ) const `[pure virtual]`

If owner is `OwnerUser` return the ID of the user who owns the file. If owner is `OwnerGroup` return the ID of the group that own the file. If you can't determine the owner return -2.

This virtual function must be reimplemented by all subclasses.

See also owner(), setFileName(), and FileOwner.

### Q_LONGLONG QFileEngine::read ( char * data, Q_LONGLONG maxSize ) `[pure virtual]`

Reads a number of characters from the file into data. At most maxSize characters will be read.

Returns -1 if a fatal error occurs, or 0 if there are no bytes to read.

### bool QFileEngine::remove () `[pure virtual]`

Requests that the file is deleted from the file system. If the operation succeeds return true; otherwise return false.

This virtual function must be reimplemented by all subclasses.

See also setFileName() and rmdir().

### bool QFileEngine::rename ( const QString & newName ) `[pure virtual]`

Requests that the file be renamed to newName in the file system. If the operation succeeds return true; otherwise return false.

This virtual function must be reimplemented by all subclasses.

See also setFileName().

### bool QFileEngine::rmdir ( const QString & dirName, QDir::Recursion recurse ) const `[pure virtual]`

Requests that the directory dirName is deleted from the file system. When recurse is `QDir::Recursive` then any empty sub-directories in dirName must also be deleted. If recurse is `QDir::NonRecursive` then only dirName should be deleted. In most file systems a directory cannot be deleted using this function if it is non-empty. If the operation succeeds return true; otherwise return false.

This virtual function must be reimplemented by all subclasses.

See also setFileName(), remove(), mkdir(), and isRelativePath().

### bool QFileEngine::seek ( QIODevice::Offset offset ) `[pure virtual]`

Sets the file position to the given offset. Returns true if the position was successfully set; otherwise returns false.

The offset is from the beginning of the file, unless the file is sequential.

See also isSequential().

### void QFileEngine::setFileName ( const QString & file ) `[pure virtual]`

Sets the file engine's file name to file. This file name is the file that the rest of the virtual functions will operate on.

This virtual function must be reimplemented by all subclasses.

See also rename().

### bool QFileEngine::setSize ( QIODevice::Offset size ) `[pure virtual]`

Requests that the file be set to size size. If size is larger than the current file then it is filled with 0's, if smaller it is simply truncated. If the operations succceeds return true; otherwise return false;

This virtual function must be reimplemented by all subclasses.

See also size().

### QIODevice::Offset QFileEngine::size () const `[pure virtual]`

Returns the size of the file.

### Type QFileEngine::type () const `[pure virtual]`

Returns the type of engine.

If you reimplement this function, the value you return should be between `User` and `MaxUser`.

### void QFileEngine::unmap ( uchar * data ) `[virtual]`

Unmap previously mapped file data from memory.

See also QFileEngine::map().

### Q_LONGLONG QFileEngine::write ( const char * data, Q_LONGLONG size ) `[pure virtual]`

Writes size bytes from data to the file. Returns the number of characters written on success; otherwise returns -1.