QFileDevice ¶

概要 ¶

详细描述 ¶

QFileDevice is the base class for I/O devices that can read and write text and binary files and resources . QFile offers the main functionality, QFileDevice serves as a base class for sharing functionality with other file devices such as QTemporaryFile , by providing all the operations that can be done on files that have been opened by QFile or QTemporaryFile .

另请参阅

QFile QTemporaryFile

class QFileDevice ¶

QFileDevice(parent)

参数

parent – QObject

PySide2.QtCore.QFileDevice. FileError ¶

此枚举描述可能的错误，错误返回通过 error() 函数。

常量	描述
QFileDevice.NoError	没有发生错误。
QFileDevice.ReadError	An error occurred when reading from the file.
QFileDevice.WriteError	An error occurred when writing to the file.
QFileDevice.FatalError	发生致命错误。
QFileDevice.ResourceError	Out of resources (e.g., too many open files, out of memory, etc.)
QFileDevice.OpenError	The file could not be opened.
QFileDevice.AbortError	The operation was aborted.
QFileDevice.TimeOutError	发生超时。
QFileDevice.UnspecifiedError	An unspecified error occurred.
QFileDevice.RemoveError	The file could not be removed.
QFileDevice.RenameError	The file could not be renamed.
QFileDevice.PositionError	The position in the file could not be changed.
QFileDevice.ResizeError	The file could not be resized.
QFileDevice.PermissionsError	The file could not be accessed.
QFileDevice.CopyError	The file could not be copied.

PySide2.QtCore.QFileDevice. FileTime ¶

This enum is used by the fileTime() and setFileTime() 函数。

常量	描述
QFileDevice.FileAccessTime	When the file was most recently accessed (e.g. read or written to).
QFileDevice.FileBirthTime	When the file was created (may not be not supported on UNIX).
QFileDevice.FileMetadataChangeTime	When the file’s metadata was last changed.
QFileDevice.FileModificationTime	When the file was most recently modified.

另请参阅

setFileTime() fileTime() fileTime()

PySide2.QtCore.QFileDevice. Permission ¶

This enum is used by the permission() function to report the permissions and ownership of a file. The values may be OR-ed together to test multiple permissions and ownership values.

常量	描述
QFileDevice.ReadOwner	The file is readable by the owner of the file.
QFileDevice.WriteOwner	The file is writable by the owner of the file.
QFileDevice.ExeOwner	The file is executable by the owner of the file.
QFileDevice.ReadUser	文件对于用户是可读的。
QFileDevice.WriteUser	文件对于用户是可写的。
QFileDevice.ExeUser	The file is executable by the user.
QFileDevice.ReadGroup	The file is readable by the group.
QFileDevice.WriteGroup	The file is writable by the group.
QFileDevice.ExeGroup	The file is executable by the group.
QFileDevice.ReadOther	The file is readable by anyone.
QFileDevice.WriteOther	The file is writable by anyone.
QFileDevice.ExeOther	The file is executable by anyone.

警告

Because of differences in the platforms supported by Qt, the semantics of , and are platform-dependent: On Unix, the rights of the owner of the file are returned and on Windows the rights of the current user are returned. This behavior might change in a future Qt version.

注意

On NTFS file systems, ownership and permissions checking is disabled by default for performance reasons. To enable it, include the following line:

extern Q_CORE_EXPORT int qt_ntfs_permission_lookup;
											

Permission checking is then turned on and off by incrementing and decrementing qt_ntfs_permission_lookup by 1.

qt_ntfs_permission_lookup += 1 // turn checking on
qt_ntfs_permission_lookup += 1 // turn it off again
											

PySide2.QtCore.QFileDevice. FileHandleFlag ¶

This enum is used when opening a file to specify additional options which only apply to files and not to a generic QIODevice .

常量	描述
QFileDevice.AutoCloseHandle	The file handle passed into open() should be closed by close() , the default behavior is that close just flushes the file and the application is responsible for closing the file handle. When opening a file by name, this flag is ignored as Qt always owns the file handle and must close it.
QFileDevice.DontCloseHandle	If not explicitly closed, the underlying file handle is left open when the QFile object is destroyed.

PySide2.QtCore.QFileDevice. MemoryMapFlags ¶

This enum describes special options that may be used by the map() 函数。

常量	描述
QFileDevice.NoOptions	没有选项。
QFileDevice.MapPrivateOption	The mapped memory will be private, so any modifications will not be visible to other processes and will not be written to disk. Any such modifications will be lost when the memory is unmapped. It is unspecified whether modifications made to the file made after the mapping is created will be visible through the mapped memory. This enum value was introduced in Qt 5.4.

PySide2.QtCore.QFileDevice. error ( ) ¶

返回类型

FileError

Returns the file error status.

I/O 设备状态返回错误代码。例如，若 open() 返回 false , or a read/write operation returns -1, this function can be called to find out the reason why the operation failed.

另请参阅

unsetError()

PySide2.QtCore.QFileDevice. fileName ( ) ¶

返回类型

unicode

Returns the name of the file. The default implementation in QFileDevice returns a null string.

PySide2.QtCore.QFileDevice. fileTime ( time ) ¶

参数

time – FileTime

返回类型

QDateTime

Returns the file time specified by time . If the time cannot be determined return QDateTime() (an invalid date time).

另请参阅

setFileTime() FileTime isValid()

PySide2.QtCore.QFileDevice. flush ( ) ¶

返回类型

bool

Flushes any buffered data to the file. Returns true 若成功；否则返回 false .

PySide2.QtCore.QFileDevice. handle ( ) ¶

返回类型

int

Returns the file handle of the file.

This is a small positive integer, suitable for use with C library functions such as fdopen() and fcntl() . On systems that use file descriptors for sockets (i.e. Unix systems, but not Windows) the handle can be used with QSocketNotifier as well.

If the file is not open, or there is an error, returns -1.

另请参阅

QSocketNotifier

PySide2.QtCore.QFileDevice. map ( offset , size [ , flags=NoOptions ] ) ¶

参数

• offset – qint64

• size – qint64

• flags – MemoryMapFlags

返回类型

PyObject

Maps size bytes of the file into memory starting at offset . A file should be open for a map to succeed but the file does not need to stay open after the memory has been mapped. When the QFile is destroyed or a new file is opened with this object, any maps that have not been unmapped will automatically be unmapped.

The mapping will have the same open mode as the file (read and/or write), except when using MapPrivateOption , in which case it is always possible to write to the mapped memory.

Any mapping options can be passed through flags .

Returns a pointer to the memory or None if there is an error.

另请参阅

unmap()

PySide2.QtCore.QFileDevice. permissions ( ) ¶

返回类型

Permissions

Returns the complete OR-ed together combination of Permission for the file.

另请参阅

setPermissions()

PySide2.QtCore.QFileDevice. resize ( sz ) ¶

参数

sz – qint64

返回类型

bool

Sets the file size (in bytes) sz 。返回 true if the resize succeeds; false otherwise. If sz is larger than the file currently is, the new bytes will be set to 0; if sz is smaller, the file is simply truncated.

警告

This function can fail if the file doesn’t exist.

另请参阅

size()

PySide2.QtCore.QFileDevice. setFileTime ( newDate , fileTime ) ¶

参数

• newDate – QDateTime

• fileTime – FileTime

返回类型

bool

Sets the file time specified by fileTime to newDate , returning true if successful; otherwise returns false.

注意

The file must be open to use this function.

另请参阅

fileTime() FileTime

PySide2.QtCore.QFileDevice. setPermissions ( permissionSpec ) ¶

参数

permissionSpec – Permissions

返回类型

bool

Sets the permissions for the file to the permissions 指定。返回 true 若成功，或 false 若权限不能被修改。

警告

此函数不操纵 ACL (访问控制列表)，这可能限制其有效性。

另请参阅

permissions()

PySide2.QtCore.QFileDevice. unmap ( address ) ¶

参数

address – uchar

返回类型

bool

取消映射内存 address .

返回 true 若取消映射成功；否则 false。

另请参阅

map()

PySide2.QtCore.QFileDevice. unsetError ( ) ¶

Sets the file’s error to NoError .

另请参阅

error()