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- from __future__ import annotations
- import select
- import socket
- import sys
- def is_socket_readable(sock: socket.socket | None) -> bool:
- """
- Return whether a socket, as identifed by its file descriptor, is readable.
- "A socket is readable" means that the read buffer isn't empty, i.e. that calling
- .recv() on it would immediately return some data.
- """
- # NOTE: we want check for readability without actually attempting to read, because
- # we don't want to block forever if it's not readable.
- # In the case that the socket no longer exists, or cannot return a file
- # descriptor, we treat it as being readable, as if it the next read operation
- # on it is ready to return the terminating `b""`.
- sock_fd = None if sock is None else sock.fileno()
- if sock_fd is None or sock_fd < 0: # pragma: nocover
- return True
- # The implementation below was stolen from:
- # https://github.com/python-trio/trio/blob/20ee2b1b7376db637435d80e266212a35837ddcc/trio/_socket.py#L471-L478
- # See also: https://github.com/encode/httpcore/pull/193#issuecomment-703129316
- # Use select.select on Windows, and when poll is unavailable and select.poll
- # everywhere else. (E.g. When eventlet is in use. See #327)
- if (
- sys.platform == "win32" or getattr(select, "poll", None) is None
- ): # pragma: nocover
- rready, _, _ = select.select([sock_fd], [], [], 0)
- return bool(rready)
- p = select.poll()
- p.register(sock_fd, select.POLLIN)
- return bool(p.poll(0))
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