mirror of
https://github.com/python/cpython
synced 2024-10-14 09:12:07 +00:00
567b26e882
PollSelector. This change is not really required in Python 3.4, since select.epoll.poll() now rounds also correctly the timeout. But Guido van Rossum prefers to have exactly the same selectors.py file in CPython and Tulip projects: "it's not harmful".
527 lines
16 KiB
Python
527 lines
16 KiB
Python
"""Selectors module.
|
|
|
|
This module allows high-level and efficient I/O multiplexing, built upon the
|
|
`select` module primitives.
|
|
"""
|
|
|
|
|
|
from abc import ABCMeta, abstractmethod
|
|
from collections import namedtuple, Mapping
|
|
import functools
|
|
import math
|
|
import select
|
|
import sys
|
|
|
|
|
|
# generic events, that must be mapped to implementation-specific ones
|
|
EVENT_READ = (1 << 0)
|
|
EVENT_WRITE = (1 << 1)
|
|
|
|
|
|
def _fileobj_to_fd(fileobj):
|
|
"""Return a file descriptor from a file object.
|
|
|
|
Parameters:
|
|
fileobj -- file object or file descriptor
|
|
|
|
Returns:
|
|
corresponding file descriptor
|
|
|
|
Raises:
|
|
ValueError if the object is invalid
|
|
"""
|
|
if isinstance(fileobj, int):
|
|
fd = fileobj
|
|
else:
|
|
try:
|
|
fd = int(fileobj.fileno())
|
|
except (AttributeError, TypeError, ValueError):
|
|
raise ValueError("Invalid file object: "
|
|
"{!r}".format(fileobj)) from None
|
|
if fd < 0:
|
|
raise ValueError("Invalid file descriptor: {}".format(fd))
|
|
return fd
|
|
|
|
|
|
SelectorKey = namedtuple('SelectorKey', ['fileobj', 'fd', 'events', 'data'])
|
|
"""Object used to associate a file object to its backing file descriptor,
|
|
selected event mask and attached data."""
|
|
|
|
|
|
class _SelectorMapping(Mapping):
|
|
"""Mapping of file objects to selector keys."""
|
|
|
|
def __init__(self, selector):
|
|
self._selector = selector
|
|
|
|
def __len__(self):
|
|
return len(self._selector._fd_to_key)
|
|
|
|
def __getitem__(self, fileobj):
|
|
try:
|
|
fd = self._selector._fileobj_lookup(fileobj)
|
|
return self._selector._fd_to_key[fd]
|
|
except KeyError:
|
|
raise KeyError("{!r} is not registered".format(fileobj)) from None
|
|
|
|
def __iter__(self):
|
|
return iter(self._selector._fd_to_key)
|
|
|
|
|
|
class BaseSelector(metaclass=ABCMeta):
|
|
"""Selector abstract base class.
|
|
|
|
A selector supports registering file objects to be monitored for specific
|
|
I/O events.
|
|
|
|
A file object is a file descriptor or any object with a `fileno()` method.
|
|
An arbitrary object can be attached to the file object, which can be used
|
|
for example to store context information, a callback, etc.
|
|
|
|
A selector can use various implementations (select(), poll(), epoll()...)
|
|
depending on the platform. The default `Selector` class uses the most
|
|
performant implementation on the current platform.
|
|
"""
|
|
|
|
@abstractmethod
|
|
def register(self, fileobj, events, data=None):
|
|
"""Register a file object.
|
|
|
|
Parameters:
|
|
fileobj -- file object or file descriptor
|
|
events -- events to monitor (bitwise mask of EVENT_READ|EVENT_WRITE)
|
|
data -- attached data
|
|
|
|
Returns:
|
|
SelectorKey instance
|
|
|
|
Raises:
|
|
ValueError if events is invalid
|
|
KeyError if fileobj is already registered
|
|
OSError if fileobj is closed or otherwise is unacceptable to
|
|
the underlying system call (if a system call is made)
|
|
|
|
Note:
|
|
OSError may or may not be raised
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
@abstractmethod
|
|
def unregister(self, fileobj):
|
|
"""Unregister a file object.
|
|
|
|
Parameters:
|
|
fileobj -- file object or file descriptor
|
|
|
|
Returns:
|
|
SelectorKey instance
|
|
|
|
Raises:
|
|
KeyError if fileobj is not registered
|
|
|
|
Note:
|
|
If fileobj is registered but has since been closed this does
|
|
*not* raise OSError (even if the wrapped syscall does)
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def modify(self, fileobj, events, data=None):
|
|
"""Change a registered file object monitored events or attached data.
|
|
|
|
Parameters:
|
|
fileobj -- file object or file descriptor
|
|
events -- events to monitor (bitwise mask of EVENT_READ|EVENT_WRITE)
|
|
data -- attached data
|
|
|
|
Returns:
|
|
SelectorKey instance
|
|
|
|
Raises:
|
|
Anything that unregister() or register() raises
|
|
"""
|
|
self.unregister(fileobj)
|
|
return self.register(fileobj, events, data)
|
|
|
|
@abstractmethod
|
|
def select(self, timeout=None):
|
|
"""Perform the actual selection, until some monitored file objects are
|
|
ready or a timeout expires.
|
|
|
|
Parameters:
|
|
timeout -- if timeout > 0, this specifies the maximum wait time, in
|
|
seconds
|
|
if timeout <= 0, the select() call won't block, and will
|
|
report the currently ready file objects
|
|
if timeout is None, select() will block until a monitored
|
|
file object becomes ready
|
|
|
|
Returns:
|
|
list of (key, events) for ready file objects
|
|
`events` is a bitwise mask of EVENT_READ|EVENT_WRITE
|
|
"""
|
|
raise NotImplementedError
|
|
|
|
def close(self):
|
|
"""Close the selector.
|
|
|
|
This must be called to make sure that any underlying resource is freed.
|
|
"""
|
|
pass
|
|
|
|
def get_key(self, fileobj):
|
|
"""Return the key associated to a registered file object.
|
|
|
|
Returns:
|
|
SelectorKey for this file object
|
|
"""
|
|
mapping = self.get_map()
|
|
try:
|
|
return mapping[fileobj]
|
|
except KeyError:
|
|
raise KeyError("{!r} is not registered".format(fileobj)) from None
|
|
|
|
@abstractmethod
|
|
def get_map(self):
|
|
"""Return a mapping of file objects to selector keys."""
|
|
raise NotImplementedError
|
|
|
|
def __enter__(self):
|
|
return self
|
|
|
|
def __exit__(self, *args):
|
|
self.close()
|
|
|
|
|
|
class _BaseSelectorImpl(BaseSelector):
|
|
"""Base selector implementation."""
|
|
|
|
def __init__(self):
|
|
# this maps file descriptors to keys
|
|
self._fd_to_key = {}
|
|
# read-only mapping returned by get_map()
|
|
self._map = _SelectorMapping(self)
|
|
|
|
def _fileobj_lookup(self, fileobj):
|
|
"""Return a file descriptor from a file object.
|
|
|
|
This wraps _fileobj_to_fd() to do an exhaustive search in case
|
|
the object is invalid but we still have it in our map. This
|
|
is used by unregister() so we can unregister an object that
|
|
was previously registered even if it is closed. It is also
|
|
used by _SelectorMapping.
|
|
"""
|
|
try:
|
|
return _fileobj_to_fd(fileobj)
|
|
except ValueError:
|
|
# Do an exhaustive search.
|
|
for key in self._fd_to_key.values():
|
|
if key.fileobj is fileobj:
|
|
return key.fd
|
|
# Raise ValueError after all.
|
|
raise
|
|
|
|
def register(self, fileobj, events, data=None):
|
|
if (not events) or (events & ~(EVENT_READ | EVENT_WRITE)):
|
|
raise ValueError("Invalid events: {!r}".format(events))
|
|
|
|
key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
|
|
|
|
if key.fd in self._fd_to_key:
|
|
raise KeyError("{!r} (FD {}) is already registered"
|
|
.format(fileobj, key.fd))
|
|
|
|
self._fd_to_key[key.fd] = key
|
|
return key
|
|
|
|
def unregister(self, fileobj):
|
|
try:
|
|
key = self._fd_to_key.pop(self._fileobj_lookup(fileobj))
|
|
except KeyError:
|
|
raise KeyError("{!r} is not registered".format(fileobj)) from None
|
|
return key
|
|
|
|
def modify(self, fileobj, events, data=None):
|
|
# TODO: Subclasses can probably optimize this even further.
|
|
try:
|
|
key = self._fd_to_key[self._fileobj_lookup(fileobj)]
|
|
except KeyError:
|
|
raise KeyError("{!r} is not registered".format(fileobj)) from None
|
|
if events != key.events:
|
|
self.unregister(fileobj)
|
|
key = self.register(fileobj, events, data)
|
|
elif data != key.data:
|
|
# Use a shortcut to update the data.
|
|
key = key._replace(data=data)
|
|
self._fd_to_key[key.fd] = key
|
|
return key
|
|
|
|
def close(self):
|
|
self._fd_to_key.clear()
|
|
|
|
def get_map(self):
|
|
return self._map
|
|
|
|
def _key_from_fd(self, fd):
|
|
"""Return the key associated to a given file descriptor.
|
|
|
|
Parameters:
|
|
fd -- file descriptor
|
|
|
|
Returns:
|
|
corresponding key, or None if not found
|
|
"""
|
|
try:
|
|
return self._fd_to_key[fd]
|
|
except KeyError:
|
|
return None
|
|
|
|
|
|
class SelectSelector(_BaseSelectorImpl):
|
|
"""Select-based selector."""
|
|
|
|
def __init__(self):
|
|
super().__init__()
|
|
self._readers = set()
|
|
self._writers = set()
|
|
|
|
def register(self, fileobj, events, data=None):
|
|
key = super().register(fileobj, events, data)
|
|
if events & EVENT_READ:
|
|
self._readers.add(key.fd)
|
|
if events & EVENT_WRITE:
|
|
self._writers.add(key.fd)
|
|
return key
|
|
|
|
def unregister(self, fileobj):
|
|
key = super().unregister(fileobj)
|
|
self._readers.discard(key.fd)
|
|
self._writers.discard(key.fd)
|
|
return key
|
|
|
|
if sys.platform == 'win32':
|
|
def _select(self, r, w, _, timeout=None):
|
|
r, w, x = select.select(r, w, w, timeout)
|
|
return r, w + x, []
|
|
else:
|
|
_select = select.select
|
|
|
|
def select(self, timeout=None):
|
|
timeout = None if timeout is None else max(timeout, 0)
|
|
ready = []
|
|
try:
|
|
r, w, _ = self._select(self._readers, self._writers, [], timeout)
|
|
except InterruptedError:
|
|
return ready
|
|
r = set(r)
|
|
w = set(w)
|
|
for fd in r | w:
|
|
events = 0
|
|
if fd in r:
|
|
events |= EVENT_READ
|
|
if fd in w:
|
|
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(_BaseSelectorImpl):
|
|
"""Poll-based selector."""
|
|
|
|
def __init__(self):
|
|
super().__init__()
|
|
self._poll = select.poll()
|
|
|
|
def register(self, fileobj, events, data=None):
|
|
key = super().register(fileobj, events, data)
|
|
poll_events = 0
|
|
if events & EVENT_READ:
|
|
poll_events |= select.POLLIN
|
|
if events & EVENT_WRITE:
|
|
poll_events |= select.POLLOUT
|
|
self._poll.register(key.fd, poll_events)
|
|
return key
|
|
|
|
def unregister(self, fileobj):
|
|
key = super().unregister(fileobj)
|
|
self._poll.unregister(key.fd)
|
|
return key
|
|
|
|
def select(self, timeout=None):
|
|
if timeout is None:
|
|
timeout = None
|
|
elif timeout <= 0:
|
|
timeout = 0
|
|
else:
|
|
# poll() has a resolution of 1 millisecond, round away from
|
|
# zero to wait *at least* timeout seconds.
|
|
timeout = int(math.ceil(timeout * 1e3))
|
|
ready = []
|
|
try:
|
|
fd_event_list = self._poll.poll(timeout)
|
|
except InterruptedError:
|
|
return ready
|
|
for fd, event in fd_event_list:
|
|
events = 0
|
|
if event & ~select.POLLIN:
|
|
events |= EVENT_WRITE
|
|
if event & ~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(_BaseSelectorImpl):
|
|
"""Epoll-based selector."""
|
|
|
|
def __init__(self):
|
|
super().__init__()
|
|
self._epoll = select.epoll()
|
|
|
|
def fileno(self):
|
|
return self._epoll.fileno()
|
|
|
|
def register(self, fileobj, events, data=None):
|
|
key = super().register(fileobj, events, data)
|
|
epoll_events = 0
|
|
if events & EVENT_READ:
|
|
epoll_events |= select.EPOLLIN
|
|
if events & EVENT_WRITE:
|
|
epoll_events |= select.EPOLLOUT
|
|
self._epoll.register(key.fd, epoll_events)
|
|
return key
|
|
|
|
def unregister(self, fileobj):
|
|
key = super().unregister(fileobj)
|
|
try:
|
|
self._epoll.unregister(key.fd)
|
|
except OSError:
|
|
# This can happen if the FD was closed since it
|
|
# was registered.
|
|
pass
|
|
return key
|
|
|
|
def select(self, timeout=None):
|
|
if timeout is None:
|
|
timeout = -1
|
|
elif timeout <= 0:
|
|
timeout = 0
|
|
else:
|
|
# epoll_wait() has a resolution of 1 millisecond, round away
|
|
# from zero to wait *at least* timeout seconds.
|
|
timeout = math.ceil(timeout * 1e3) * 1e-3
|
|
max_ev = len(self._fd_to_key)
|
|
ready = []
|
|
try:
|
|
fd_event_list = self._epoll.poll(timeout, max_ev)
|
|
except InterruptedError:
|
|
return ready
|
|
for fd, event in fd_event_list:
|
|
events = 0
|
|
if event & ~select.EPOLLIN:
|
|
events |= EVENT_WRITE
|
|
if event & ~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().close()
|
|
|
|
|
|
if hasattr(select, 'kqueue'):
|
|
|
|
class KqueueSelector(_BaseSelectorImpl):
|
|
"""Kqueue-based selector."""
|
|
|
|
def __init__(self):
|
|
super().__init__()
|
|
self._kqueue = select.kqueue()
|
|
|
|
def fileno(self):
|
|
return self._kqueue.fileno()
|
|
|
|
def register(self, fileobj, events, data=None):
|
|
key = super().register(fileobj, events, data)
|
|
if events & EVENT_READ:
|
|
kev = select.kevent(key.fd, select.KQ_FILTER_READ,
|
|
select.KQ_EV_ADD)
|
|
self._kqueue.control([kev], 0, 0)
|
|
if events & EVENT_WRITE:
|
|
kev = select.kevent(key.fd, select.KQ_FILTER_WRITE,
|
|
select.KQ_EV_ADD)
|
|
self._kqueue.control([kev], 0, 0)
|
|
return key
|
|
|
|
def unregister(self, fileobj):
|
|
key = super().unregister(fileobj)
|
|
if key.events & EVENT_READ:
|
|
kev = select.kevent(key.fd, select.KQ_FILTER_READ,
|
|
select.KQ_EV_DELETE)
|
|
try:
|
|
self._kqueue.control([kev], 0, 0)
|
|
except OSError:
|
|
# This can happen if the FD was closed since it
|
|
# was registered.
|
|
pass
|
|
if key.events & EVENT_WRITE:
|
|
kev = select.kevent(key.fd, select.KQ_FILTER_WRITE,
|
|
select.KQ_EV_DELETE)
|
|
try:
|
|
self._kqueue.control([kev], 0, 0)
|
|
except OSError:
|
|
# See comment above.
|
|
pass
|
|
return key
|
|
|
|
def select(self, timeout=None):
|
|
timeout = None if timeout is None else max(timeout, 0)
|
|
max_ev = len(self._fd_to_key)
|
|
ready = []
|
|
try:
|
|
kev_list = self._kqueue.control(None, max_ev, timeout)
|
|
except InterruptedError:
|
|
return ready
|
|
for kev in kev_list:
|
|
fd = kev.ident
|
|
flag = kev.filter
|
|
events = 0
|
|
if flag == select.KQ_FILTER_READ:
|
|
events |= EVENT_READ
|
|
if flag == select.KQ_FILTER_WRITE:
|
|
events |= EVENT_WRITE
|
|
|
|
key = self._key_from_fd(fd)
|
|
if key:
|
|
ready.append((key, events & key.events))
|
|
return ready
|
|
|
|
def close(self):
|
|
self._kqueue.close()
|
|
super().close()
|
|
|
|
|
|
# Choose the best implementation: roughly, epoll|kqueue > poll > select.
|
|
# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
|
|
if 'KqueueSelector' in globals():
|
|
DefaultSelector = KqueueSelector
|
|
elif 'EpollSelector' in globals():
|
|
DefaultSelector = EpollSelector
|
|
elif 'PollSelector' in globals():
|
|
DefaultSelector = PollSelector
|
|
else:
|
|
DefaultSelector = SelectSelector
|