PollableInputStream

Added in version 2.28.

class PollableInputStream(*args, **kwargs)

Implementations: ConverterInputStream, MemoryInputStream, UnixInputStream

GPollableInputStream is implemented by InputStream’s that can be polled for readiness to read. This can be used when interfacing with a non-GIO API that expects UNIX-file-descriptor-style asynchronous I/O rather than GIO-style.

Some classes may implement GPollableInputStream but have only certain instances of that class be pollable. If can_poll returns false, then the behavior of other GPollableInputStream methods is undefined.

Methods

class PollableInputStream

can_poll() → bool

Checks if stream is actually pollable. Some classes may implement PollableInputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other PollableInputStream methods is undefined.

For any given stream, the value returned by this method is constant; a stream cannot switch from pollable to non-pollable or vice versa.

Added in version 2.28.

create_source(cancellable: Cancellable | None = None) → Source

Creates a Source that triggers when stream can be read, or cancellable is triggered or an error occurs. The callback on the source is of the GPollableSourceFunc type.

As with is_readable(), it is possible that the stream may not actually be readable even after the source triggers, so you should use read_nonblocking() rather than read() from the callback.

The behaviour of this method is undefined if can_poll() returns False for stream.

Added in version 2.28.

Parameters:

cancellable – a Cancellable, or None

is_readable() → bool

Checks if stream can be read.

Note that some stream types may not be able to implement this 100% reliably, and it is possible that a call to read() after this returns True would still block. To guarantee non-blocking behavior, you should always use read_nonblocking(), which will return a WOULD_BLOCK error rather than blocking.

The behaviour of this method is undefined if can_poll() returns False for stream.

Added in version 2.28.

read_nonblocking(cancellable: Cancellable | None = None) → tuple[int, bytes]

Attempts to read up to count bytes from stream into buffer, as with read(). If stream is not currently readable, this will immediately return WOULD_BLOCK, and you can use create_source() to create a Source that will be triggered when stream is readable.

Note that since this method never blocks, you cannot actually use cancellable to cancel it. However, it will return an error if cancellable has already been cancelled when you call, which may happen if you call this method after a source triggers due to having been cancelled.

The behaviour of this method is undefined if can_poll() returns False for stream.

Parameters:

cancellable – a Cancellable, or None

Virtual Methods

class PollableInputStream

do_can_poll() → bool

Checks if stream is actually pollable. Some classes may implement PollableInputStream but have only certain instances of that class be pollable. If this method returns False, then the behavior of other PollableInputStream methods is undefined.

For any given stream, the value returned by this method is constant; a stream cannot switch from pollable to non-pollable or vice versa.

Added in version 2.28.

do_create_source(cancellable: Cancellable | None = None) → Source

Creates a Source that triggers when stream can be read, or cancellable is triggered or an error occurs. The callback on the source is of the GPollableSourceFunc type.

As with is_readable(), it is possible that the stream may not actually be readable even after the source triggers, so you should use read_nonblocking() rather than read() from the callback.

The behaviour of this method is undefined if can_poll() returns False for stream.

Added in version 2.28.

Parameters:

cancellable – a Cancellable, or None

do_is_readable() → bool

Checks if stream can be read.

Note that some stream types may not be able to implement this 100% reliably, and it is possible that a call to read() after this returns True would still block. To guarantee non-blocking behavior, you should always use read_nonblocking(), which will return a WOULD_BLOCK error rather than blocking.

The behaviour of this method is undefined if can_poll() returns False for stream.

Added in version 2.28.

do_read_nonblocking() → tuple[int, bytes]

Attempts to read up to count bytes from stream into buffer, as with read(). If stream is not currently readable, this will immediately return WOULD_BLOCK, and you can use create_source() to create a Source that will be triggered when stream is readable.

Note that since this method never blocks, you cannot actually use cancellable to cancel it. However, it will return an error if cancellable has already been cancelled when you call, which may happen if you call this method after a source triggers due to having been cancelled.

The behaviour of this method is undefined if can_poll() returns False for stream.