Seekable

class Seekable(*args, **kwargs)

Implementations: BufferedInputStream, BufferedOutputStream, DataInputStream, DataOutputStream, FileIOStream, FileInputStream, FileOutputStream, MemoryInputStream, MemoryOutputStream

GSeekable is implemented by streams (implementations of InputStream or OutputStream) that support seeking.

Seekable streams largely fall into two categories: resizable and fixed-size.

GSeekable on fixed-sized streams is approximately the same as POSIX `lseek() <man:lseek(2>`_) on a block device (for example: attempting to seek past the end of the device is an error). Fixed streams typically cannot be truncated.

GSeekable on resizable streams is approximately the same as POSIX `lseek() <man:lseek(2>`_) on a normal file. Seeking past the end and writing data will usually cause the stream to resize by introducing zero bytes.

Methods

class Seekable
can_seek() → bool

Tests if the stream supports the GSeekableIface.

can_truncate() → bool

Tests if the length of the stream can be adjusted with truncate().

seek(offset: int, type: SeekType, cancellable: Cancellable | None = None) → bool

Seeks in the stream by the given offset, modified by type.

Attempting to seek past the end of the stream will have different results depending on if the stream is fixed-sized or resizable. If the stream is resizable then seeking past the end and then writing will result in zeros filling the empty space. Seeking past the end of a resizable stream and reading will result in EOF. Seeking past the end of a fixed-sized stream will fail.

Any operation that would result in a negative offset will fail.

If cancellable is not None, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error CANCELLED will be returned.

Parameters:

  • offset – a gint64.

  • type – a SeekType.

  • cancellable – optional Cancellable object, None to ignore.

tell() → int

Tells the current position within the stream.

truncate(offset: int, cancellable: Cancellable | None = None) → bool

Sets the length of the stream to offset. If the stream was previously larger than offset, the extra data is discarded. If the stream was previously shorter than offset, it is extended with NUL (’0’) bytes.

If cancellable is not None, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

Parameters:

  • offset – new length for seekable, in bytes.

  • cancellable – optional Cancellable object, None to ignore.

Virtual Methods

class Seekable
do_can_seek() → bool

Tests if the stream supports the GSeekableIface.

do_can_truncate() → bool

Tests if the length of the stream can be adjusted with truncate().

do_seek(offset: int, type: SeekType, cancellable: Cancellable | None = None) → bool

Seeks in the stream by the given offset, modified by type.

Attempting to seek past the end of the stream will have different results depending on if the stream is fixed-sized or resizable. If the stream is resizable then seeking past the end and then writing will result in zeros filling the empty space. Seeking past the end of a resizable stream and reading will result in EOF. Seeking past the end of a fixed-sized stream will fail.

Any operation that would result in a negative offset will fail.

If cancellable is not None, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error CANCELLED will be returned.

Parameters:

  • offset – a gint64.

  • type – a SeekType.

  • cancellable – optional Cancellable object, None to ignore.

do_tell() → int

Tells the current position within the stream.

do_truncate_fn(offset: int, cancellable: Cancellable | None = None) → bool

Sets the length of the stream to offset. If the stream was previously larger than offset, the extra data is discarded. If the stream was previously shorter than offset, it is extended with NUL (’0’) bytes.

If cancellable is not None, then the operation can be cancelled by triggering the cancellable object from another thread. If the operation was cancelled, the error CANCELLED will be returned. If an operation was partially finished when the operation was cancelled the partial result will be returned, without an error.

Parameters:

  • offset – new length for seekable, in bytes.

  • cancellable – optional Cancellable object, None to ignore.