IOStream

Added in version 2.22.

class IOStream(**properties: Any)

Superclasses: Object

Subclasses: FileIOStream, SimpleIOStream, SocketConnection, TlsConnection

GIOStream represents an object that has both read and write streams. Generally the two streams act as separate input and output streams, but they share some common resources and state. For instance, for seekable streams, both streams may use the same position.

Examples of GIOStream objects are SocketConnection, which represents a two-way network connection; and FileIOStream, which represents a file handle opened in read-write mode.

To do the actual reading and writing you need to get the substreams with get_input_stream and get_output_stream.

The GIOStream object owns the input and the output streams, not the other way around, so keeping the substreams alive will not keep the GIOStream object alive. If the GIOStream object is freed it will be closed, thus closing the substreams, so even if the substreams stay alive they will always return G_IO_ERROR_CLOSED for all operations.

To close a stream use close which will close the common stream object and also the individual substreams. You can also close the substreams themselves. In most cases this only marks the substream as closed, so further I/O on it fails but common state in the GIOStream may still be open. However, some streams may support ‘half-closed’ states where one direction of the stream is actually shut down.

Operations on GIOStream’s cannot be started while another operation on the GIOStream or its substreams is in progress. Specifically, an application can read from the InputStream and write to the OutputStream simultaneously (either in separate threads, or as asynchronous operations in the same thread), but an application cannot start any GIOStream operation while there is a GIOStream, GInputStream or GOutputStream operation in progress, and an application can’t start any GInputStream or GOutputStream operation while there is a GIOStream operation in progress.

This is a product of individual stream operations being associated with a given MainContext (the thread-default context at the time the operation was started), rather than entire streams being associated with a single GMainContext.

GIO may run operations on GIOStream’s from other (worker) threads, and this may be exposed to application code in the behaviour of wrapper streams, such as BufferedInputStream or TlsConnection. With such wrapper APIs, application code may only run operations on the base (wrapped) stream when the wrapper stream is idle. Note that the semantics of such operations may not be well-defined due to the state the wrapper stream leaves the base stream in (though they are guaranteed not to crash).

Methods

class IOStream
clear_pending() → None

Clears the pending flag on stream.

Added in version 2.22.

close(cancellable: Cancellable | None = None) → bool

Closes the stream, releasing resources related to it. This will also close the individual input and output streams, if they are not already closed.

Once the stream is closed, all other operations will return CLOSED. Closing a stream multiple times will not return an error.

Closing a stream will automatically flush any outstanding buffers in the stream.

Streams will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Some streams might keep the backing store of the stream (e.g. a file descriptor) open after the stream is closed. See the documentation for the individual stream for details.

On failure the first error that happened will be reported, but the close operation will finish as much as possible. A stream that failed to close will still return CLOSED for all operations. Still, it is important to check and report the error to the user, otherwise there might be a loss of data as all data might not be written.

If cancellable is not NULL, 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. Cancelling a close will still leave the stream closed, but some streams can use a faster close that doesn’t block to e.g. check errors.

The default implementation of this method just calls close on the individual input/output streams.

Added in version 2.22.

Parameters:

cancellable – optional Cancellable object, None to ignore

close_async(io_priority: int, cancellable: Cancellable | None = None, callback: Callable[[...], None] | None = None, *user_data: Any) → None

Requests an asynchronous close of the stream, releasing resources related to it. When the operation is finished callback will be called. You can then call close_finish() to get the result of the operation.

For behaviour details see close().

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

Added in version 2.22.

Parameters:

  • io_priority – the io priority of the request

  • cancellable – optional cancellable object

  • callback – a AsyncReadyCallback to call when the request is satisfied

  • user_data – the data to pass to callback function

close_finish(result: AsyncResult) → bool

Closes a stream.

Added in version 2.22.

Parameters:

result – a AsyncResult

get_input_stream() → InputStream

Gets the input stream for this object. This is used for reading.

Added in version 2.22.

get_output_stream() → OutputStream

Gets the output stream for this object. This is used for writing.

Added in version 2.22.

has_pending() → bool

Checks if a stream has pending actions.

Added in version 2.22.

is_closed() → bool

Checks if a stream is closed.

Added in version 2.22.

set_pending() → bool

Sets stream to have actions pending. If the pending flag is already set or stream is closed, it will return False and set error.

Added in version 2.22.

splice_async(stream2: IOStream, flags: IOStreamSpliceFlags, io_priority: int, cancellable: Cancellable | None = None, callback: Callable[[...], None] | None = None, *user_data: Any) → None

Asynchronously splice the output stream of stream1 to the input stream of stream2, and splice the output stream of stream2 to the input stream of stream1.

When the operation is finished callback will be called. You can then call splice_finish() to get the result of the operation.

Added in version 2.28.

Parameters:

  • stream2 – a IOStream.

  • flags – a set of IOStreamSpliceFlags.

  • io_priority – the io priority of the request.

  • cancellable – optional Cancellable object, None to ignore.

  • callback – a AsyncReadyCallback to call when the request is satisfied

  • user_data – the data to pass to callback function

splice_finish(result: AsyncResult) → bool

Finishes an asynchronous io stream splice operation.

Added in version 2.28.

Parameters:

result – a AsyncResult.

Properties

class IOStream
props.closed: bool

Whether the stream is closed.

Added in version 2.22.

props.input_stream: InputStream

The InputStream to read from.

Added in version 2.22.

props.output_stream: OutputStream

The OutputStream to write to.

Added in version 2.22.

Virtual Methods

class IOStream
do_close_async(io_priority: int, cancellable: Cancellable | None = None, callback: Callable[[...], None] | None = None, *user_data: Any) → None

Requests an asynchronous close of the stream, releasing resources related to it. When the operation is finished callback will be called. You can then call close_finish() to get the result of the operation.

For behaviour details see close().

The asynchronous methods have a default fallback that uses threads to implement asynchronicity, so they are optional for inheriting classes. However, if you override one you must override all.

Added in version 2.22.

Parameters:

  • io_priority – the io priority of the request

  • cancellable – optional cancellable object

  • callback – a AsyncReadyCallback to call when the request is satisfied

  • user_data – the data to pass to callback function

do_close_finish(result: AsyncResult) → bool

Closes a stream.

Added in version 2.22.

Parameters:

result – a AsyncResult

do_close_fn(cancellable: Cancellable | None = None) → bool
Parameters:

cancellable

do_get_input_stream() → InputStream

Gets the input stream for this object. This is used for reading.

Added in version 2.22.

do_get_output_stream() → OutputStream

Gets the output stream for this object. This is used for writing.

Added in version 2.22.

Fields

class IOStream
parent_instance
priv