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