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582 lines
21 KiB
582 lines
21 KiB
6 years ago
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# Backport of selectors.py from Python 3.5+ to support Python < 3.4
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# Also has the behavior specified in PEP 475 which is to retry syscalls
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# in the case of an EINTR error. This module is required because selectors34
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# does not follow this behavior and instead returns that no dile descriptor
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# events have occurred rather than retry the syscall. The decision to drop
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# support for select.devpoll is made to maintain 100% test coverage.
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import errno
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import math
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import select
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import socket
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import sys
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import time
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from collections import namedtuple, Mapping
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try:
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monotonic = time.monotonic
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except (AttributeError, ImportError): # Python 3.3<
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monotonic = time.time
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EVENT_READ = (1 << 0)
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EVENT_WRITE = (1 << 1)
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HAS_SELECT = True # Variable that shows whether the platform has a selector.
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_SYSCALL_SENTINEL = object() # Sentinel in case a system call returns None.
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_DEFAULT_SELECTOR = None
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class SelectorError(Exception):
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def __init__(self, errcode):
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super(SelectorError, self).__init__()
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self.errno = errcode
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def __repr__(self):
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return "<SelectorError errno={0}>".format(self.errno)
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def __str__(self):
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return self.__repr__()
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def _fileobj_to_fd(fileobj):
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""" Return a file descriptor from a file object. If
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given an integer will simply return that integer back. """
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if isinstance(fileobj, int):
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fd = fileobj
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else:
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try:
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fd = int(fileobj.fileno())
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except (AttributeError, TypeError, ValueError):
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raise ValueError("Invalid file object: {0!r}".format(fileobj))
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if fd < 0:
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raise ValueError("Invalid file descriptor: {0}".format(fd))
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return fd
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# Determine which function to use to wrap system calls because Python 3.5+
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# already handles the case when system calls are interrupted.
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if sys.version_info >= (3, 5):
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def _syscall_wrapper(func, _, *args, **kwargs):
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""" This is the short-circuit version of the below logic
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because in Python 3.5+ all system calls automatically restart
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and recalculate their timeouts. """
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try:
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return func(*args, **kwargs)
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except (OSError, IOError, select.error) as e:
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errcode = None
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if hasattr(e, "errno"):
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errcode = e.errno
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raise SelectorError(errcode)
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else:
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def _syscall_wrapper(func, recalc_timeout, *args, **kwargs):
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""" Wrapper function for syscalls that could fail due to EINTR.
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All functions should be retried if there is time left in the timeout
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in accordance with PEP 475. """
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timeout = kwargs.get("timeout", None)
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if timeout is None:
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expires = None
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recalc_timeout = False
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else:
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timeout = float(timeout)
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if timeout < 0.0: # Timeout less than 0 treated as no timeout.
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expires = None
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else:
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expires = monotonic() + timeout
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args = list(args)
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if recalc_timeout and "timeout" not in kwargs:
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raise ValueError(
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"Timeout must be in args or kwargs to be recalculated")
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result = _SYSCALL_SENTINEL
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while result is _SYSCALL_SENTINEL:
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try:
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result = func(*args, **kwargs)
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# OSError is thrown by select.select
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# IOError is thrown by select.epoll.poll
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# select.error is thrown by select.poll.poll
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# Aren't we thankful for Python 3.x rework for exceptions?
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except (OSError, IOError, select.error) as e:
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# select.error wasn't a subclass of OSError in the past.
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errcode = None
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if hasattr(e, "errno"):
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errcode = e.errno
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elif hasattr(e, "args"):
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errcode = e.args[0]
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# Also test for the Windows equivalent of EINTR.
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is_interrupt = (errcode == errno.EINTR or (hasattr(errno, "WSAEINTR") and
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errcode == errno.WSAEINTR))
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if is_interrupt:
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if expires is not None:
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current_time = monotonic()
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if current_time > expires:
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raise OSError(errno=errno.ETIMEDOUT)
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if recalc_timeout:
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if "timeout" in kwargs:
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kwargs["timeout"] = expires - current_time
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continue
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if errcode:
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raise SelectorError(errcode)
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else:
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raise
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return result
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SelectorKey = namedtuple('SelectorKey', ['fileobj', 'fd', 'events', 'data'])
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class _SelectorMapping(Mapping):
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""" Mapping of file objects to selector keys """
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def __init__(self, selector):
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self._selector = selector
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def __len__(self):
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return len(self._selector._fd_to_key)
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def __getitem__(self, fileobj):
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try:
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fd = self._selector._fileobj_lookup(fileobj)
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return self._selector._fd_to_key[fd]
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except KeyError:
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raise KeyError("{0!r} is not registered.".format(fileobj))
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def __iter__(self):
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return iter(self._selector._fd_to_key)
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class BaseSelector(object):
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""" Abstract Selector class
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A selector supports registering file objects to be monitored
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for specific I/O events.
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A file object is a file descriptor or any object with a
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`fileno()` method. An arbitrary object can be attached to the
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file object which can be used for example to store context info,
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a callback, etc.
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A selector can use various implementations (select(), poll(), epoll(),
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and kqueue()) depending on the platform. The 'DefaultSelector' class uses
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the most efficient implementation for the current platform.
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"""
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def __init__(self):
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# Maps file descriptors to keys.
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self._fd_to_key = {}
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# Read-only mapping returned by get_map()
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self._map = _SelectorMapping(self)
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def _fileobj_lookup(self, fileobj):
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""" Return a file descriptor from a file object.
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This wraps _fileobj_to_fd() to do an exhaustive
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search in case the object is invalid but we still
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have it in our map. Used by unregister() so we can
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unregister an object that was previously registered
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even if it is closed. It is also used by _SelectorMapping
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"""
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try:
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return _fileobj_to_fd(fileobj)
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except ValueError:
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# Search through all our mapped keys.
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for key in self._fd_to_key.values():
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if key.fileobj is fileobj:
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return key.fd
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# Raise ValueError after all.
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raise
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def register(self, fileobj, events, data=None):
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""" Register a file object for a set of events to monitor. """
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if (not events) or (events & ~(EVENT_READ | EVENT_WRITE)):
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raise ValueError("Invalid events: {0!r}".format(events))
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key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
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if key.fd in self._fd_to_key:
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raise KeyError("{0!r} (FD {1}) is already registered"
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.format(fileobj, key.fd))
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self._fd_to_key[key.fd] = key
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return key
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def unregister(self, fileobj):
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""" Unregister a file object from being monitored. """
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try:
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key = self._fd_to_key.pop(self._fileobj_lookup(fileobj))
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except KeyError:
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raise KeyError("{0!r} is not registered".format(fileobj))
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# Getting the fileno of a closed socket on Windows errors with EBADF.
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except socket.error as e: # Platform-specific: Windows.
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if e.errno != errno.EBADF:
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raise
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else:
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for key in self._fd_to_key.values():
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if key.fileobj is fileobj:
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self._fd_to_key.pop(key.fd)
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break
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else:
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raise KeyError("{0!r} is not registered".format(fileobj))
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return key
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def modify(self, fileobj, events, data=None):
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""" Change a registered file object monitored events and data. """
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# NOTE: Some subclasses optimize this operation even further.
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try:
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key = self._fd_to_key[self._fileobj_lookup(fileobj)]
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except KeyError:
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raise KeyError("{0!r} is not registered".format(fileobj))
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if events != key.events:
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self.unregister(fileobj)
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key = self.register(fileobj, events, data)
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elif data != key.data:
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# Use a shortcut to update the data.
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key = key._replace(data=data)
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self._fd_to_key[key.fd] = key
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return key
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def select(self, timeout=None):
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""" Perform the actual selection until some monitored file objects
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are ready or the timeout expires. """
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raise NotImplementedError()
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def close(self):
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""" Close the selector. This must be called to ensure that all
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underlying resources are freed. """
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self._fd_to_key.clear()
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self._map = None
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def get_key(self, fileobj):
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""" Return the key associated with a registered file object. """
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mapping = self.get_map()
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if mapping is None:
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raise RuntimeError("Selector is closed")
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try:
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return mapping[fileobj]
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except KeyError:
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raise KeyError("{0!r} is not registered".format(fileobj))
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def get_map(self):
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""" Return a mapping of file objects to selector keys """
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return self._map
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def _key_from_fd(self, fd):
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""" Return the key associated to a given file descriptor
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Return None if it is not found. """
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try:
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return self._fd_to_key[fd]
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except KeyError:
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return None
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def __enter__(self):
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return self
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def __exit__(self, *args):
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self.close()
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# Almost all platforms have select.select()
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if hasattr(select, "select"):
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class SelectSelector(BaseSelector):
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""" Select-based selector. """
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def __init__(self):
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super(SelectSelector, self).__init__()
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self._readers = set()
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self._writers = set()
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def register(self, fileobj, events, data=None):
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key = super(SelectSelector, self).register(fileobj, events, data)
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if events & EVENT_READ:
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self._readers.add(key.fd)
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if events & EVENT_WRITE:
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self._writers.add(key.fd)
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return key
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||
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def unregister(self, fileobj):
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||
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key = super(SelectSelector, self).unregister(fileobj)
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self._readers.discard(key.fd)
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self._writers.discard(key.fd)
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return key
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||
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|
def _select(self, r, w, timeout=None):
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|
""" Wrapper for select.select because timeout is a positional arg """
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||
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|
return select.select(r, w, [], timeout)
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||
|
|
|
||
|
|
def select(self, timeout=None):
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||
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|
# Selecting on empty lists on Windows errors out.
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||
|
|
if not len(self._readers) and not len(self._writers):
|
||
|
|
return []
|
||
|
|
|
||
|
|
timeout = None if timeout is None else max(timeout, 0.0)
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||
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|
ready = []
|
||
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|
r, w, _ = _syscall_wrapper(self._select, True, self._readers,
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|
|
self._writers, timeout)
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||
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|
r = set(r)
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||
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|
w = set(w)
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||
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|
for fd in r | w:
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||
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|
events = 0
|
||
|
|
if fd in r:
|
||
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|
events |= EVENT_READ
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||
|
|
if fd in w:
|
||
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|
events |= EVENT_WRITE
|
||
|
|
|
||
|
|
key = self._key_from_fd(fd)
|
||
|
|
if key:
|
||
|
|
ready.append((key, events & key.events))
|
||
|
|
return ready
|
||
|
|
|
||
|
|
|
||
|
|
if hasattr(select, "poll"):
|
||
|
|
class PollSelector(BaseSelector):
|
||
|
|
""" Poll-based selector """
|
||
|
|
def __init__(self):
|
||
|
|
super(PollSelector, self).__init__()
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||
|
|
self._poll = select.poll()
|
||
|
|
|
||
|
|
def register(self, fileobj, events, data=None):
|
||
|
|
key = super(PollSelector, self).register(fileobj, events, data)
|
||
|
|
event_mask = 0
|
||
|
|
if events & EVENT_READ:
|
||
|
|
event_mask |= select.POLLIN
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||
|
|
if events & EVENT_WRITE:
|
||
|
|
event_mask |= select.POLLOUT
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||
|
|
self._poll.register(key.fd, event_mask)
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||
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|
return key
|
||
|
|
|
||
|
|
def unregister(self, fileobj):
|
||
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|
key = super(PollSelector, self).unregister(fileobj)
|
||
|
|
self._poll.unregister(key.fd)
|
||
|
|
return key
|
||
|
|
|
||
|
|
def _wrap_poll(self, timeout=None):
|
||
|
|
""" Wrapper function for select.poll.poll() so that
|
||
|
|
_syscall_wrapper can work with only seconds. """
|
||
|
|
if timeout is not None:
|
||
|
|
if timeout <= 0:
|
||
|
|
timeout = 0
|
||
|
|
else:
|
||
|
|
# select.poll.poll() has a resolution of 1 millisecond,
|
||
|
|
# round away from zero to wait *at least* timeout seconds.
|
||
|
|
timeout = math.ceil(timeout * 1e3)
|
||
|
|
|
||
|
|
result = self._poll.poll(timeout)
|
||
|
|
return result
|
||
|
|
|
||
|
|
def select(self, timeout=None):
|
||
|
|
ready = []
|
||
|
|
fd_events = _syscall_wrapper(self._wrap_poll, True, timeout=timeout)
|
||
|
|
for fd, event_mask in fd_events:
|
||
|
|
events = 0
|
||
|
|
if event_mask & ~select.POLLIN:
|
||
|
|
events |= EVENT_WRITE
|
||
|
|
if event_mask & ~select.POLLOUT:
|
||
|
|
events |= EVENT_READ
|
||
|
|
|
||
|
|
key = self._key_from_fd(fd)
|
||
|
|
if key:
|
||
|
|
ready.append((key, events & key.events))
|
||
|
|
|
||
|
|
return ready
|
||
|
|
|
||
|
|
|
||
|
|
if hasattr(select, "epoll"):
|
||
|
|
class EpollSelector(BaseSelector):
|
||
|
|
""" Epoll-based selector """
|
||
|
|
def __init__(self):
|
||
|
|
super(EpollSelector, self).__init__()
|
||
|
|
self._epoll = select.epoll()
|
||
|
|
|
||
|
|
def fileno(self):
|
||
|
|
return self._epoll.fileno()
|
||
|
|
|
||
|
|
def register(self, fileobj, events, data=None):
|
||
|
|
key = super(EpollSelector, self).register(fileobj, events, data)
|
||
|
|
events_mask = 0
|
||
|
|
if events & EVENT_READ:
|
||
|
|
events_mask |= select.EPOLLIN
|
||
|
|
if events & EVENT_WRITE:
|
||
|
|
events_mask |= select.EPOLLOUT
|
||
|
|
_syscall_wrapper(self._epoll.register, False, key.fd, events_mask)
|
||
|
|
return key
|
||
|
|
|
||
|
|
def unregister(self, fileobj):
|
||
|
|
key = super(EpollSelector, self).unregister(fileobj)
|
||
|
|
try:
|
||
|
|
_syscall_wrapper(self._epoll.unregister, False, key.fd)
|
||
|
|
except SelectorError:
|
||
|
|
# This can occur when the fd was closed since registry.
|
||
|
|
pass
|
||
|
|
return key
|
||
|
|
|
||
|
|
def select(self, timeout=None):
|
||
|
|
if timeout is not None:
|
||
|
|
if timeout <= 0:
|
||
|
|
timeout = 0.0
|
||
|
|
else:
|
||
|
|
# select.epoll.poll() has a resolution of 1 millisecond
|
||
|
|
# but luckily takes seconds so we don't need a wrapper
|
||
|
|
# like PollSelector. Just for better rounding.
|
||
|
|
timeout = math.ceil(timeout * 1e3) * 1e-3
|
||
|
|
timeout = float(timeout)
|
||
|
|
else:
|
||
|
|
timeout = -1.0 # epoll.poll() must have a float.
|
||
|
|
|
||
|
|
# We always want at least 1 to ensure that select can be called
|
||
|
|
# with no file descriptors registered. Otherwise will fail.
|
||
|
|
max_events = max(len(self._fd_to_key), 1)
|
||
|
|
|
||
|
|
ready = []
|
||
|
|
fd_events = _syscall_wrapper(self._epoll.poll, True,
|
||
|
|
timeout=timeout,
|
||
|
|
maxevents=max_events)
|
||
|
|
for fd, event_mask in fd_events:
|
||
|
|
events = 0
|
||
|
|
if event_mask & ~select.EPOLLIN:
|
||
|
|
events |= EVENT_WRITE
|
||
|
|
if event_mask & ~select.EPOLLOUT:
|
||
|
|
events |= EVENT_READ
|
||
|
|
|
||
|
|
key = self._key_from_fd(fd)
|
||
|
|
if key:
|
||
|
|
ready.append((key, events & key.events))
|
||
|
|
return ready
|
||
|
|
|
||
|
|
def close(self):
|
||
|
|
self._epoll.close()
|
||
|
|
super(EpollSelector, self).close()
|
||
|
|
|
||
|
|
|
||
|
|
if hasattr(select, "kqueue"):
|
||
|
|
class KqueueSelector(BaseSelector):
|
||
|
|
""" Kqueue / Kevent-based selector """
|
||
|
|
def __init__(self):
|
||
|
|
super(KqueueSelector, self).__init__()
|
||
|
|
self._kqueue = select.kqueue()
|
||
|
|
|
||
|
|
def fileno(self):
|
||
|
|
return self._kqueue.fileno()
|
||
|
|
|
||
|
|
def register(self, fileobj, events, data=None):
|
||
|
|
key = super(KqueueSelector, self).register(fileobj, events, data)
|
||
|
|
if events & EVENT_READ:
|
||
|
|
kevent = select.kevent(key.fd,
|
||
|
|
select.KQ_FILTER_READ,
|
||
|
|
select.KQ_EV_ADD)
|
||
|
|
|
||
|
|
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
|
||
|
|
|
||
|
|
if events & EVENT_WRITE:
|
||
|
|
kevent = select.kevent(key.fd,
|
||
|
|
select.KQ_FILTER_WRITE,
|
||
|
|
select.KQ_EV_ADD)
|
||
|
|
|
||
|
|
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
|
||
|
|
|
||
|
|
return key
|
||
|
|
|
||
|
|
def unregister(self, fileobj):
|
||
|
|
key = super(KqueueSelector, self).unregister(fileobj)
|
||
|
|
if key.events & EVENT_READ:
|
||
|
|
kevent = select.kevent(key.fd,
|
||
|
|
select.KQ_FILTER_READ,
|
||
|
|
select.KQ_EV_DELETE)
|
||
|
|
try:
|
||
|
|
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
|
||
|
|
except SelectorError:
|
||
|
|
pass
|
||
|
|
if key.events & EVENT_WRITE:
|
||
|
|
kevent = select.kevent(key.fd,
|
||
|
|
select.KQ_FILTER_WRITE,
|
||
|
|
select.KQ_EV_DELETE)
|
||
|
|
try:
|
||
|
|
_syscall_wrapper(self._kqueue.control, False, [kevent], 0, 0)
|
||
|
|
except SelectorError:
|
||
|
|
pass
|
||
|
|
|
||
|
|
return key
|
||
|
|
|
||
|
|
def select(self, timeout=None):
|
||
|
|
if timeout is not None:
|
||
|
|
timeout = max(timeout, 0)
|
||
|
|
|
||
|
|
max_events = len(self._fd_to_key) * 2
|
||
|
|
ready_fds = {}
|
||
|
|
|
||
|
|
kevent_list = _syscall_wrapper(self._kqueue.control, True,
|
||
|
|
None, max_events, timeout)
|
||
|
|
|
||
|
|
for kevent in kevent_list:
|
||
|
|
fd = kevent.ident
|
||
|
|
event_mask = kevent.filter
|
||
|
|
events = 0
|
||
|
|
if event_mask == select.KQ_FILTER_READ:
|
||
|
|
events |= EVENT_READ
|
||
|
|
if event_mask == select.KQ_FILTER_WRITE:
|
||
|
|
events |= EVENT_WRITE
|
||
|
|
|
||
|
|
key = self._key_from_fd(fd)
|
||
|
|
if key:
|
||
|
|
if key.fd not in ready_fds:
|
||
|
|
ready_fds[key.fd] = (key, events & key.events)
|
||
|
|
else:
|
||
|
|
old_events = ready_fds[key.fd][1]
|
||
|
|
ready_fds[key.fd] = (key, (events | old_events) & key.events)
|
||
|
|
|
||
|
|
return list(ready_fds.values())
|
||
|
|
|
||
|
|
def close(self):
|
||
|
|
self._kqueue.close()
|
||
|
|
super(KqueueSelector, self).close()
|
||
|
|
|
||
|
|
|
||
|
|
if not hasattr(select, 'select'): # Platform-specific: AppEngine
|
||
|
|
HAS_SELECT = False
|
||
|
|
|
||
|
|
|
||
|
|
def _can_allocate(struct):
|
||
|
|
""" Checks that select structs can be allocated by the underlying
|
||
|
|
operating system, not just advertised by the select module. We don't
|
||
|
|
check select() because we'll be hopeful that most platforms that
|
||
|
|
don't have it available will not advertise it. (ie: GAE) """
|
||
|
|
try:
|
||
|
|
# select.poll() objects won't fail until used.
|
||
|
|
if struct == 'poll':
|
||
|
|
p = select.poll()
|
||
|
|
p.poll(0)
|
||
|
|
|
||
|
|
# All others will fail on allocation.
|
||
|
|
else:
|
||
|
|
getattr(select, struct)().close()
|
||
|
|
return True
|
||
|
|
except (OSError, AttributeError) as e:
|
||
|
|
return False
|
||
|
|
|
||
|
|
|
||
|
|
# Choose the best implementation, roughly:
|
||
|
|
# kqueue == epoll > poll > select. Devpoll not supported. (See above)
|
||
|
|
# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
|
||
|
|
def DefaultSelector():
|
||
|
|
""" This function serves as a first call for DefaultSelector to
|
||
|
|
detect if the select module is being monkey-patched incorrectly
|
||
|
|
by eventlet, greenlet, and preserve proper behavior. """
|
||
|
|
global _DEFAULT_SELECTOR
|
||
|
|
if _DEFAULT_SELECTOR is None:
|
||
|
|
if _can_allocate('kqueue'):
|
||
|
|
_DEFAULT_SELECTOR = KqueueSelector
|
||
|
|
elif _can_allocate('epoll'):
|
||
|
|
_DEFAULT_SELECTOR = EpollSelector
|
||
|
|
elif _can_allocate('poll'):
|
||
|
|
_DEFAULT_SELECTOR = PollSelector
|
||
|
|
elif hasattr(select, 'select'):
|
||
|
|
_DEFAULT_SELECTOR = SelectSelector
|
||
|
|
else: # Platform-specific: AppEngine
|
||
|
|
raise ValueError('Platform does not have a selector')
|
||
|
|
return _DEFAULT_SELECTOR()
|