内容

• 公共类型
• 公共函数
• 静态公共成员
• 保护函数
• 相关非成员
• 详细描述

QAbstractFileEngine Class

The QAbstractFileEngine class provides an abstraction for accessing the filesystem. 更多...

头：	#include <QAbstractFileEngine>
Since:	Qt 4.1
继承者：	QFSFileEngine

注意： 此类的所有函数 可重入 .

• 所有成员列表，包括继承成员

公共类型

class	ExtensionOption
class	ExtensionReturn
class	MapExtensionOption
class	MapExtensionReturn
class	UnMapExtensionOption
enum	Extension { AtEndExtension, FastReadLineExtension, MapExtension, UnMapExtension }
enum	FileFlag { ReadOwnerPerm, WriteOwnerPerm, ExeOwnerPerm, ReadUserPerm, ..., Refresh }
flags	FileFlags
enum	FileName { DefaultName, BaseName, PathName, AbsoluteName, ..., BundleName }
enum	FileOwner { OwnerUser, OwnerGroup }
enum	FileTime { CreationTime, ModificationTime, AccessTime }
typedef	Iterator

公共函数

virtual	~QAbstractFileEngine ()
bool	atEnd () const
virtual Iterator *	beginEntryList (QDir::Filters filters , const QStringList & filterNames )
virtual bool	caseSensitive () const
virtual bool	close ()
virtual bool	copy (const QString & newName )
virtual QStringList	entryList (QDir::Filters filters , const QStringList & filterNames ) const
QFile::FileError	error () const
QString	errorString () const
virtual bool	extension (Extension extension , const ExtensionOption * option = 0, ExtensionReturn * output = 0)
virtual FileFlags	fileFlags (FileFlags type = FileInfoAll) const
virtual QString	fileName (FileName file = DefaultName) const
virtual QDateTime	fileTime (FileTime time ) const
virtual bool	flush ()
virtual int	handle () const
virtual bool	isRelativePath () const
virtual bool	isSequential () const
virtual bool	link (const QString & newName )
uchar *	map (qint64 offset , qint64 size , QFile::MemoryMapFlags flags )
virtual bool	mkdir (const QString & dirName , bool createParentDirectories ) const
virtual bool	open (QIODevice::OpenMode mode )
virtual QString	owner (FileOwner owner ) const
virtual uint	ownerId (FileOwner owner ) const
virtual qint64	pos () const
virtual qint64	read (char * data , qint64 maxlen )
virtual qint64	readLine (char * data , qint64 maxlen )
virtual bool	remove ()
virtual bool	rename (const QString & newName )
virtual bool	rmdir (const QString & dirName , bool recurseParentDirectories ) const
virtual bool	seek (qint64 offset )
virtual void	setFileName (const QString & file )
virtual bool	setPermissions (uint perms )
virtual bool	setSize (qint64 size )
virtual qint64	size () const
virtual bool	supportsExtension (Extension extension ) const
bool	unmap (uchar * address )
virtual qint64	write (const char * data , qint64 len )

静态公共成员

QAbstractFileEngine *

create (const QString & fileName )

保护函数

	QAbstractFileEngine ()
void	setError (QFile::FileError error , const QString & errorString )

相关非成员

typedef

Iterator

详细描述

The QAbstractFileEngine class provides an abstraction for accessing the filesystem.

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

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

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

另请参阅 QAbstractFileEngineHandler .

成员类型文档编制

enum QAbstractFileEngine:: Extension

This enum describes the types of extensions that the file engine can support. Before using these extensions, you must verify that the extension is supported (i.e., call supportsExtension ()).

常量	值	描述
QAbstractFileEngine::AtEndExtension	0	Whether the current file position is at the end of the file or not. This extension allows file engines that implement local buffering to report end-of-file status without having to check the size of the file. It is also useful for sequential files, where the size of the file cannot be used to determine whether or not you have reached the end. This extension returns true if the file is at the end; otherwise it returns false. The input and output arguments to extension () 被忽略。
QAbstractFileEngine::FastReadLineExtension	1	Whether the file engine provides a fast implementation for readLine () or not. If readLine () remains unimplemented in the file engine, QAbstractFileEngine will provide an implementation based on calling read () repeatedly. If supportsExtension () returns false for this extension, however, QIODevice can provide a faster implementation by making use of its internal buffer. For engines that already provide a fast readLine () implementation, returning false for this extension can avoid unnnecessary double-buffering in QIODevice .
QAbstractFileEngine::MapExtension	2	Whether the file engine provides the ability to map a file to memory.
QAbstractFileEngine::UnMapExtension	3	Whether the file engine provides the ability to unmap memory that was previously mapped.

该枚举在 Qt 4.3 引入或被修改。

enum QAbstractFileEngine:: FileFlag
flags QAbstractFileEngine:: FileFlags

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

常量	值	描述
QAbstractFileEngine::ReadOwnerPerm	0x4000	The owner of the file has permission to read it.
QAbstractFileEngine::WriteOwnerPerm	0x2000	The owner of the file has permission to write to it.
QAbstractFileEngine::ExeOwnerPerm	0x1000	The owner of the file has permission to execute it.
QAbstractFileEngine::ReadUserPerm	0x0400	The current user has permission to read the file.
QAbstractFileEngine::WriteUserPerm	0x0200	The current user has permission to write to the file.
QAbstractFileEngine::ExeUserPerm	0x0100	The current user has permission to execute the file.
QAbstractFileEngine::ReadGroupPerm	0x0040	Members of the current user's group have permission to read the file.
QAbstractFileEngine::WriteGroupPerm	0x0020	Members of the current user's group have permission to write to the file.
QAbstractFileEngine::ExeGroupPerm	0x0010	Members of the current user's group have permission to execute the file.
QAbstractFileEngine::ReadOtherPerm	0x0004	All users have permission to read the file.
QAbstractFileEngine::WriteOtherPerm	0x0002	All users have permission to write to the file.
QAbstractFileEngine::ExeOtherPerm	0x0001	All users have permission to execute the file.
QAbstractFileEngine::LinkType	0x10000	The file is a link to another file (or link) in the file system (i.e. not a file or directory).
QAbstractFileEngine::FileType	0x20000	The file is a regular file to the file system (i.e. not a link or directory)
QAbstractFileEngine::BundleType	0x80000	The file is a Mac OS X bundle implies DirectoryType
QAbstractFileEngine::DirectoryType	0x40000	The file is a directory in the file system (i.e. not a link or file).
QAbstractFileEngine::HiddenFlag	0x0100000	The file is hidden.
QAbstractFileEngine::ExistsFlag	0x0400000	The file actually exists in the file system.
QAbstractFileEngine::RootFlag	0x0800000	The file or the file pointed to is the root of the filesystem.
QAbstractFileEngine::LocalDiskFlag	0x0200000	The file resides on the local disk and can be passed to standard file functions.
QAbstractFileEngine::Refresh	0x1000000	Passing this flag will force the file engine to refresh all flags.

The FileFlags type is a typedef for QFlags <FileFlag>. It stores an OR combination of FileFlag values.

另请参阅 fileFlags () 和 setFileName ().

enum QAbstractFileEngine:: FileName

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

常量	值	描述
QAbstractFileEngine::DefaultName	0	The same filename that was passed to the QAbstractFileEngine .
QAbstractFileEngine::BaseName	1	The name of the file excluding the path.
QAbstractFileEngine::PathName	2	The path to the file excluding the base name.
QAbstractFileEngine::AbsoluteName	3	The absolute path to the file (including the base name).
QAbstractFileEngine::AbsolutePathName	4	The absolute path to the file (excluding the base name).
QAbstractFileEngine::LinkName	5	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.)
QAbstractFileEngine::CanonicalName	6	Often very similar to LinkName. Will return the true path to the file.
QAbstractFileEngine::CanonicalPathName	7	Same as CanonicalName, excluding the base name.
QAbstractFileEngine::BundleName	8	Returns the name of the bundle implies BundleType 有设置。

另请参阅 fileName () 和 setFileName ().

enum QAbstractFileEngine:: FileOwner

常量	值	描述
QAbstractFileEngine::OwnerUser	0	The user who owns the file.
QAbstractFileEngine::OwnerGroup	1	The group who owns the file.

另请参阅 owner (), ownerId ()，和 setFileName ().

enum QAbstractFileEngine:: FileTime

These are used by the fileTime () 函数。

常量	值	描述
QAbstractFileEngine::CreationTime	0	When the file was created.
QAbstractFileEngine::ModificationTime	1	最近修改文件时。
QAbstractFileEngine::AccessTime	2	最近访问文件时 (如：读写)。

另请参阅 setFileName ().

typedef QAbstractFileEngine:: Iterator

同义词 QAbstractFileEngineIterator .

This typedef was introduced in Qt 4.3.

成员函数文档编制

[protected] QAbstractFileEngine:: QAbstractFileEngine ()

构造新的 QAbstractFileEngine that does not refer to any file or directory.

另请参阅 setFileName ().

[虚拟] QAbstractFileEngine:: ~QAbstractFileEngine ()

销毁 QAbstractFileEngine .

bool QAbstractFileEngine:: atEnd () const

Returns true if the current position is at the end of the file; otherwise, returns false.

This function bases its behavior on calling extension () 采用 AtEndExtension . If the engine does not support this extension, false is returned.

该函数在 Qt 4.3 引入。

另请参阅 extension (), supportsExtension ()，和 QFile::atEnd ().

[虚拟] Iterator * QAbstractFileEngine:: beginEntryList ( QDir::Filters filters , const QStringList & filterNames )

Returns an instance of a QAbstractFileEngineIterator 使用 filters for entry filtering and filterNames for name filtering. This function is called by QDirIterator to initiate directory iteration.

QDirIterator takes ownership of the returned instance, and deletes it when it's done.

另请参阅 QDirIterator .

[虚拟] bool QAbstractFileEngine:: caseSensitive () const

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

This virtual function must be reimplemented by all subclasses.

[虚拟] bool QAbstractFileEngine:: close ()

Closes the file, returning true if successful; otherwise returns false.

The default implementation always returns false.

[虚拟] bool QAbstractFileEngine:: copy (const QString & newName )

Copies the contents of this file to a file with the name newName . Returns true on success; otherwise, false is returned.

[static] QAbstractFileEngine * QAbstractFileEngine:: create (const QString & fileName )

创建并返回 QAbstractFileEngine suitable for processing fileName .

You should not need to call this function; use QFile , QFileInfo or QDir directly instead.

If you reimplemnt this function, it should only return file engines that knows how to handle fileName ; otherwise, it should return 0.

另请参阅 QAbstractFileEngineHandler .

[虚拟] QStringList QAbstractFileEngine:: entryList ( QDir::Filters filters , const QStringList & filterNames ) const

Requests that a list of all the files matching the filters list based on the filterNames 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.

另请参阅 setFileName ().

QFile::FileError QAbstractFileEngine:: error () const

返回 QFile::FileError that resulted from the last failed operation. If QFile::UnspecifiedError is returned, QFile will use its own idea of the error status.

另请参阅 setError (), QFile::FileError ，和 errorString ().

QString QAbstractFileEngine:: errorString () const

返回人类可读消息适合当前报告错误通过 error ()。若没有合适字符串可用，返回空字符串。

另请参阅 error ().

[虚拟] bool QAbstractFileEngine:: extension ( Extension extension , const ExtensionOption * option = 0, ExtensionReturn * output = 0)

This virtual function can be reimplemented in a QAbstractFileEngine subclass to provide support for extensions. The option argument is provided as input to the extension, and this function can store output results in output .

The behavior of this function is determined by extension ; see the Extension documentation for details.

可以调用 supportsExtension () to check if an extension is supported by the file engine.

By default, no extensions are supported, and this function returns false.

该函数在 Qt 4.3 引入。

另请参阅 supportsExtension () 和 Extension .

[虚拟] FileFlags QAbstractFileEngine:: fileFlags ( FileFlags type = FileInfoAll) const

This function should return the set of OR'd flags 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.

另请参阅 setFileName ().

[虚拟] QString QAbstractFileEngine:: fileName ( FileName file = DefaultName) const

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.

另请参阅 setFileName () 和 FileName .

[虚拟] QDateTime QAbstractFileEngine:: fileTime ( FileTime time ) const

若 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.

另请参阅 setFileName (), QDateTime , QDateTime::isValid ()，和 FileTime .

[虚拟] bool QAbstractFileEngine:: flush ()

Flushes the open file, returning true if successful; otherwise returns false.

The default implementation always returns false.

[虚拟] int QAbstractFileEngine:: handle () const

Returns the native file handle for this file engine. This handle must be used with care; its value and type are platform specific, and using it will most likely lead to non-portable code.

[虚拟] bool QAbstractFileEngine:: isRelativePath () const

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.

另请参阅 setFileName ().

[虚拟] bool QAbstractFileEngine:: isSequential () const

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.

[虚拟] bool QAbstractFileEngine:: link (const QString & newName )

Creates a link from the file currently specified by fileName () 到 newName . What a link is depends on the underlying filesystem (be it a shortcut on Windows or a symbolic link on Unix). Returns true if successful; otherwise returns false.

uchar * QAbstractFileEngine:: map ( qint64 offset , qint64 size , QFile::MemoryMapFlags flags )

映射 size 字节的文件到内存起始于 offset . Returns a pointer to the memory if successful; otherwise returns false if, for example, an error occurs.

This function bases its behavior on calling extension () 采用 MapExtensionOption . If the engine does not support this extension, 0 is returned.

flags is currently not used, but could be used in the future.

该函数在 Qt 4.4 引入。

另请参阅 unmap () 和 supportsExtension ().

[虚拟] bool QAbstractFileEngine:: mkdir (const QString & dirName , bool createParentDirectories ) const

Requests that the directory dirName be created. If createParentDirectories is true, then any sub-directories in dirName that don't exist must be created. If createParentDirectories is false 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.

另请参阅 setFileName (), rmdir ()，和 isRelativePath ().

[虚拟] bool QAbstractFileEngine:: open ( QIODevice::OpenMode mode )

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.

[虚拟] QString QAbstractFileEngine:: owner ( FileOwner owner ) const

若 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.

另请参阅 ownerId (), setFileName ()，和 FileOwner .

[虚拟] uint QAbstractFileEngine:: ownerId ( FileOwner owner ) const

若 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.

另请参阅 owner (), setFileName ()，和 FileOwner .

[虚拟] qint64 QAbstractFileEngine:: pos () const

Returns the current file position.

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

[虚拟] qint64 QAbstractFileEngine:: read ( char * data , qint64 maxlen )

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

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

[虚拟] qint64 QAbstractFileEngine:: readLine ( char * data , qint64 maxlen )

This function reads one line, terminated by a '\n' character, from the file info data . At most maxlen characters will be read. The end-of-line character is included.

[虚拟] bool QAbstractFileEngine:: remove ()

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.

另请参阅 setFileName () 和 rmdir ().

[虚拟] bool QAbstractFileEngine:: rename (const QString & newName )

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.

另请参阅 setFileName ().

[虚拟] bool QAbstractFileEngine:: rmdir (const QString & dirName , bool recurseParentDirectories ) const

Requests that the directory dirName is deleted from the file system. When recurseParentDirectories is true, then any empty parent-directories in dirName must also be deleted. If recurseParentDirectories is false, only the dirName leaf-node 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.

另请参阅 setFileName (), remove (), mkdir ()，和 isRelativePath ().

[虚拟] bool QAbstractFileEngine:: seek ( qint64 offset )

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.

另请参阅 isSequential ().

[protected] void QAbstractFileEngine:: setError ( QFile::FileError error , const QString & errorString )

Sets the error type to error , and the error string to errorString . Call this function to set the error values returned by the higher-level classes.

另请参阅 QFile::error (), QIODevice::errorString ()，和 QIODevice::setErrorString ().

[虚拟] void QAbstractFileEngine:: setFileName (const QString & file )

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.

另请参阅 fileName () 和 rename ().

[虚拟] bool QAbstractFileEngine:: setPermissions ( uint perms )

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

This virtual function must be reimplemented by all subclasses.

另请参阅 size ().

[虚拟] bool QAbstractFileEngine:: setSize ( qint64 size )

Requests that the file be set to size size 。若 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.

另请参阅 size ().

[虚拟] qint64 QAbstractFileEngine:: size () const

返回文件大小。

另请参阅 setSize ().

[虚拟] bool QAbstractFileEngine:: supportsExtension ( Extension extension ) const

This virtual function returns true if the file engine supports extension ; otherwise, false is returned. By default, no extensions are supported.

该函数在 Qt 4.3 引入。

另请参阅 extension ().

bool QAbstractFileEngine:: unmap ( uchar * address )

取消映射内存 address . Returns true if the unmap succeeds; otherwise returns false.

This function bases its behavior on calling extension () 采用 UnMapExtensionOption . If the engine does not support this extension, false is returned.

该函数在 Qt 4.4 引入。

另请参阅 map () 和 supportsExtension ().

[虚拟] qint64 QAbstractFileEngine:: write (const char * data , qint64 len )

写入 len 字节来自 data to the file. Returns the number of characters written on success; otherwise returns -1.

相关非成员

typedef QAbstractFileEngine:: Iterator

同义词 QAbstractFileEngineIterator .

This typedef was introduced in Qt 4.3.