codekingpro/portable-devtools

1from __future__ import annotations2 3import select4import socket5import sys6 7 8def is_socket_readable(sock: socket.socket | None) -> bool:9    """10    Return whether a socket, as identifed by its file descriptor, is readable.11    "A socket is readable" means that the read buffer isn't empty, i.e. that calling12    .recv() on it would immediately return some data.13    """14    # NOTE: we want check for readability without actually attempting to read, because15    # we don't want to block forever if it's not readable.16 17    # In the case that the socket no longer exists, or cannot return a file18    # descriptor, we treat it as being readable, as if it the next read operation19    # on it is ready to return the terminating `b""`.20    sock_fd = None if sock is None else sock.fileno()21    if sock_fd is None or sock_fd < 0:  # pragma: nocover22        return True23 24    # The implementation below was stolen from:25    # https://github.com/python-trio/trio/blob/20ee2b1b7376db637435d80e266212a35837ddcc/trio/_socket.py#L471-L47826    # See also: https://github.com/encode/httpcore/pull/193#issuecomment-70312931627 28    # Use select.select on Windows, and when poll is unavailable and select.poll29    # everywhere else. (E.g. When eventlet is in use. See #327)30    if (31        sys.platform == "win32" or getattr(select, "poll", None) is None32    ):  # pragma: nocover33        rready, _, _ = select.select([sock_fd], [], [], 0)34        return bool(rready)35    p = select.poll()36    p.register(sock_fd, select.POLLIN)37    return bool(p.poll(0))38