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Issue #6397: Support '/dev/poll' polling objects in select module, under Solaris & derivatives.
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‎Doc/library/select.rst‎

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This module provides access to the :c:func:`select` and :c:func:`poll` functions
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available in most operating systems, :c:func:`epoll` available on Linux 2.5+ and
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available in most operating systems, :c:func:`devpoll` available on
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Solaris and derivatives, :c:func:`epoll` available on Linux 2.5+ and
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:c:func:`kqueue` available on most BSD.
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Note that on Windows, it only works for sockets; on other operating systems,
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it also works for other file types (in particular, on Unix, it works on pipes).
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Following :pep:`3151`, this class was made an alias of :exc:`OSError`.
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.. function:: devpoll()
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(Only supported on Solaris and derivatives.) Returns a ``/dev/poll``
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polling object; see section :ref:`devpoll-objects` below for the
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methods supported by devpoll objects.
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:c:func:`devpoll` objects are linked to the number of file
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descriptors allowed at the time of instantiation. If your program
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reduces this value, :c:func:`devpoll` will fail. If your program
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increases this value, c:func:`devpoll` may return an
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incomplete list of active file descriptors.
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.. versionadded:: 3.3
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.. function:: epoll(sizehint=-1)
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(Only supported on Linux 2.5.44 and newer.) Returns an edge polling object,
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.. versionadded:: 3.2
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.. _devpoll-objects:
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``/dev/poll`` Polling Objects
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----------------------------------------------
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http://developers.sun.com/solaris/articles/using_devpoll.html
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http://developers.sun.com/solaris/articles/polling_efficient.html
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Solaris and derivatives have ``/dev/poll``. While :c:func:`select` is
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O(highest file descriptor) and :c:func:`poll` is O(number of file
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descriptors), ``/dev/poll`` is O(active file descriptors).
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``/dev/poll`` behaviour is very close to the standard :c:func:`poll`
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object.
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.. method:: devpoll.register(fd[, eventmask])
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Register a file descriptor with the polling object. Future calls to the
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:meth:`poll` method will then check whether the file descriptor has any pending
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I/O events. *fd* can be either an integer, or an object with a :meth:`fileno`
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method that returns an integer. File objects implement :meth:`fileno`, so they
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can also be used as the argument.
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*eventmask* is an optional bitmask describing the type of events you want to
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check for. The constants are the same that with :c:func:`poll`
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object. The default value is a combination of the constants :const:`POLLIN`,
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:const:`POLLPRI`, and :const:`POLLOUT`.
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.. warning::
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Registering a file descriptor that's already registered is not an
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error, but the result is undefined. The appropiate action is to
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unregister or modify it first. This is an important difference
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compared with :c:func:`poll`.
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.. method:: devpoll.modify(fd[, eventmask])
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This method does an :meth:`unregister` followed by a
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:meth:`register`. It is (a bit) more efficient that doing the same
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explicitly.
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.. method:: devpoll.unregister(fd)
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Remove a file descriptor being tracked by a polling object. Just like the
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:meth:`register` method, *fd* can be an integer or an object with a
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:meth:`fileno` method that returns an integer.
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Attempting to remove a file descriptor that was never registered is
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safely ignored.
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.. method:: devpoll.poll([timeout])
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Polls the set of registered file descriptors, and returns a possibly-empty list
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containing ``(fd, event)`` 2-tuples for the descriptors that have events or
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errors to report. *fd* is the file descriptor, and *event* is a bitmask with
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bits set for the reported events for that descriptor --- :const:`POLLIN` for
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waiting input, :const:`POLLOUT` to indicate that the descriptor can be written
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to, and so forth. An empty list indicates that the call timed out and no file
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descriptors had any events to report. If *timeout* is given, it specifies the
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length of time in milliseconds which the system will wait for events before
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returning. If *timeout* is omitted, -1, or :const:`None`, the call will
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block until there is an event for this poll object.
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.. _epoll-objects:
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Edge and Level Trigger Polling (epoll) Objects

‎Lib/test/test_devpoll.py‎

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# Test case for the select.devpoll() function
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# Initial tests are copied as is from "test_poll.py"
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import os, select, random, unittest, sys
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from test.support import TESTFN, run_unittest
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try:
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select.devpoll
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except AttributeError:
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raise unittest.SkipTest("select.devpoll not defined -- skipping test_devpoll")
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def find_ready_matching(ready, flag):
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match = []
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for fd, mode in ready:
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if mode & flag:
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match.append(fd)
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return match
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class DevPollTests(unittest.TestCase):
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def test_devpoll1(self):
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# Basic functional test of poll object
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# Create a bunch of pipe and test that poll works with them.
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p = select.devpoll()
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NUM_PIPES = 12
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MSG = b" This is a test."
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MSG_LEN = len(MSG)
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readers = []
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writers = []
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r2w = {}
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w2r = {}
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for i in range(NUM_PIPES):
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rd, wr = os.pipe()
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p.register(rd)
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p.modify(rd, select.POLLIN)
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p.register(wr, select.POLLOUT)
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readers.append(rd)
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writers.append(wr)
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r2w[rd] = wr
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w2r[wr] = rd
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bufs = []
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while writers:
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ready = p.poll()
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ready_writers = find_ready_matching(ready, select.POLLOUT)
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if not ready_writers:
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self.fail("no pipes ready for writing")
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wr = random.choice(ready_writers)
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os.write(wr, MSG)
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ready = p.poll()
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ready_readers = find_ready_matching(ready, select.POLLIN)
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if not ready_readers:
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self.fail("no pipes ready for reading")
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self.assertEqual([w2r[wr]], ready_readers)
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rd = ready_readers[0]
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buf = os.read(rd, MSG_LEN)
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self.assertEqual(len(buf), MSG_LEN)
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bufs.append(buf)
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os.close(r2w[rd]) ; os.close(rd)
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p.unregister(r2w[rd])
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p.unregister(rd)
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writers.remove(r2w[rd])
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self.assertEqual(bufs, [MSG] * NUM_PIPES)
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def test_timeout_overflow(self):
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pollster = select.devpoll()
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w, r = os.pipe()
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pollster.register(w)
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pollster.poll(-1)
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self.assertRaises(OverflowError, pollster.poll, -2)
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self.assertRaises(OverflowError, pollster.poll, -1 << 31)
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self.assertRaises(OverflowError, pollster.poll, -1 << 64)
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pollster.poll(0)
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pollster.poll(1)
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pollster.poll(1 << 30)
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self.assertRaises(OverflowError, pollster.poll, 1 << 31)
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self.assertRaises(OverflowError, pollster.poll, 1 << 63)
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self.assertRaises(OverflowError, pollster.poll, 1 << 64)
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def test_main():
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run_unittest(DevPollTests)
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if __name__ == '__main__':
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test_main()

‎Misc/NEWS‎

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Library
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-------
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- Issue #6397: Support "/dev/poll" polling objects in select module,
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under Solaris & derivatives.
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- Issues #1745761, #755670, #13357, #12629, #1200313: HTMLParser now correctly
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handles non-valid attributes, including adjacent and unquoted attributes.
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