track embedded python distribution

1 files changed, 1132 insertions, 0 deletions

diff --git a/python/gevent/libev/corecffi.py b/python/gevent/libev/corecffi.py
new file mode 100644
index 0000000..7283fb4
--- /dev/null
+++ b/python/gevent/libev/corecffi.py
@@ -0,0 +1,1132 @@
+# pylint:disable=too-many-lines, protected-access, redefined-outer-name, not-callable,
+# pylint:disable=no-member
+from __future__ import absolute_import, print_function
+import sys
+import os
+import traceback
+import signal as signalmodule
+
+# pylint:disable=undefined-all-variable
+__all__ = [
+    'get_version',
+    'get_header_version',
+    'supported_backends',
+    'recommended_backends',
+    'embeddable_backends',
+    'time',
+    'loop',
+]
+
+import gevent.libev._corecffi as _corecffi # pylint:disable=no-name-in-module
+
+ffi = _corecffi.ffi # pylint:disable=no-member
+libev = _corecffi.lib # pylint:disable=no-member
+
+if hasattr(libev, 'vfd_open'):
+    # Must be on windows
+    assert sys.platform.startswith("win"), "vfd functions only needed on windows"
+    vfd_open = libev.vfd_open
+    vfd_free = libev.vfd_free
+    vfd_get = libev.vfd_get
+else:
+    vfd_open = vfd_free = vfd_get = lambda fd: fd
+
+#####
+## NOTE on Windows:
+# The C implementation does several things specially for Windows;
+# a possibly incomplete list is:
+#
+# - the loop runs a periodic signal checker;
+# - the io watcher constructor is different and it has a destructor;
+# - the child watcher is not defined
+#
+# The CFFI implementation does none of these things, and so
+# is possibly NOT FUNCTIONALLY CORRECT on Win32
+#####
+
+#####
+## Note on CFFI objects, callbacks and the lifecycle of watcher objects
+#
+# Each subclass of `watcher` allocates a C structure of the
+# appropriate type e.g., struct gevent_ev_io and holds this pointer in
+# its `_gwatcher` attribute. When that watcher instance is garbage
+# collected, then the C structure is also freed. The C structure is
+# passed to libev from the watcher's start() method and then to the
+# appropriate C callback function, e.g., _gevent_ev_io_callback, which
+# passes it back to python's _python_callback where we need the
+# watcher instance. Therefore, as long as that callback is active (the
+# watcher is started), the watcher instance must not be allowed to get
+# GC'd---any access at the C level or even the FFI level to the freed
+# memory could crash the process.
+#
+# However, the typical idiom calls for writing something like this:
+#  loop.io(fd, python_cb).start()
+# thus forgetting the newly created watcher subclass and allowing it to be immediately
+# GC'd. To combat this, when the watcher is started, it places itself into the loop's
+# `_keepaliveset`, and it only removes itself when the watcher's `stop()` method is called.
+# Often, this is the *only* reference keeping the watcher object, and hence its C structure,
+# alive.
+#
+# This is slightly complicated by the fact that the python-level
+# callback, called from the C callback, could choose to manually stop
+# the watcher. When we return to the C level callback, we now have an
+# invalid pointer, and attempting to pass it back to Python (e.g., to
+# handle an error) could crash. Hence, _python_callback,
+# _gevent_io_callback, and _python_handle_error cooperate to make sure
+# that the watcher instance stays in the loops `_keepaliveset` while
+# the C code could be running---and if it gets removed, to not call back
+# to Python again.
+# See also https://github.com/gevent/gevent/issues/676
+####
+
+
+@ffi.callback("int(void* handle, int revents)")
+def _python_callback(handle, revents):
+    """
+    Returns an integer having one of three values:
+
+    - -1
+      An exception occurred during the callback and you must call
+      :func:`_python_handle_error` to deal with it. The Python watcher
+      object will have the exception tuple saved in ``_exc_info``.
+    - 0
+      Everything went according to plan. You should check to see if the libev
+      watcher is still active, and call :func:`_python_stop` if so. This will
+      clean up the memory.
+    - 1
+      Everything went according to plan, but the watcher has already
+      been stopped. Its memory may no longer be valid.
+    """
+    try:
+        # Even dereferencing the handle needs to be inside the try/except;
+        # if we don't return normally (e.g., a signal) then we wind up going
+        # to the 'onerror' handler, which
+        # is not what we want; that can permanently wedge the loop depending
+        # on which callback was executing
+        the_watcher = ffi.from_handle(handle)
+        args = the_watcher.args
+        if args is None:
+            # Legacy behaviour from corecext: convert None into ()
+            # See test__core_watcher.py
+            args = _NOARGS
+        if args and args[0] == GEVENT_CORE_EVENTS:
+            args = (revents, ) + args[1:]
+        the_watcher.callback(*args)
+    except: # pylint:disable=bare-except
+        the_watcher._exc_info = sys.exc_info()
+        # Depending on when the exception happened, the watcher
+        # may or may not have been stopped. We need to make sure its
+        # memory stays valid so we can stop it at the ev level if needed.
+        the_watcher.loop._keepaliveset.add(the_watcher)
+        return -1
+    else:
+        if the_watcher in the_watcher.loop._keepaliveset:
+            # It didn't stop itself
+            return 0
+        return 1 # It stopped itself
+libev.python_callback = _python_callback
+
+
+@ffi.callback("void(void* handle, int revents)")
+def _python_handle_error(handle, revents):
+    try:
+        watcher = ffi.from_handle(handle)
+        exc_info = watcher._exc_info
+        del watcher._exc_info
+        watcher.loop.handle_error(watcher, *exc_info)
+    finally:
+        # XXX Since we're here on an error condition, and we
+        # made sure that the watcher object was put in loop._keepaliveset,
+        # what about not stopping the watcher? Looks like a possible
+        # memory leak?
+        if revents & (libev.EV_READ | libev.EV_WRITE):
+            try:
+                watcher.stop()
+            except: # pylint:disable=bare-except
+                watcher.loop.handle_error(watcher, *sys.exc_info())
+            return # pylint:disable=lost-exception
+libev.python_handle_error = _python_handle_error
+
+
+@ffi.callback("void(void* handle)")
+def _python_stop(handle):
+    watcher = ffi.from_handle(handle)
+    watcher.stop()
+libev.python_stop = _python_stop
+
+
+UNDEF = libev.EV_UNDEF
+NONE = libev.EV_NONE
+READ = libev.EV_READ
+WRITE = libev.EV_WRITE
+TIMER = libev.EV_TIMER
+PERIODIC = libev.EV_PERIODIC
+SIGNAL = libev.EV_SIGNAL
+CHILD = libev.EV_CHILD
+STAT = libev.EV_STAT
+IDLE = libev.EV_IDLE
+PREPARE = libev.EV_PREPARE
+CHECK = libev.EV_CHECK
+EMBED = libev.EV_EMBED
+FORK = libev.EV_FORK
+CLEANUP = libev.EV_CLEANUP
+ASYNC = libev.EV_ASYNC
+CUSTOM = libev.EV_CUSTOM
+ERROR = libev.EV_ERROR
+
+READWRITE = libev.EV_READ | libev.EV_WRITE
+
+MINPRI = libev.EV_MINPRI
+MAXPRI = libev.EV_MAXPRI
+
+BACKEND_PORT = libev.EVBACKEND_PORT
+BACKEND_KQUEUE = libev.EVBACKEND_KQUEUE
+BACKEND_EPOLL = libev.EVBACKEND_EPOLL
+BACKEND_POLL = libev.EVBACKEND_POLL
+BACKEND_SELECT = libev.EVBACKEND_SELECT
+FORKCHECK = libev.EVFLAG_FORKCHECK
+NOINOTIFY = libev.EVFLAG_NOINOTIFY
+SIGNALFD = libev.EVFLAG_SIGNALFD
+NOSIGMASK = libev.EVFLAG_NOSIGMASK
+
+
+class _EVENTSType(object):
+    def __repr__(self):
+        return 'gevent.core.EVENTS'
+
+EVENTS = GEVENT_CORE_EVENTS = _EVENTSType()
+
+
+def get_version():
+    return 'libev-%d.%02d' % (libev.ev_version_major(), libev.ev_version_minor())
+
+
+def get_header_version():
+    return 'libev-%d.%02d' % (libev.EV_VERSION_MAJOR, libev.EV_VERSION_MINOR)
+
+_flags = [(libev.EVBACKEND_PORT, 'port'),
+          (libev.EVBACKEND_KQUEUE, 'kqueue'),
+          (libev.EVBACKEND_EPOLL, 'epoll'),
+          (libev.EVBACKEND_POLL, 'poll'),
+          (libev.EVBACKEND_SELECT, 'select'),
+          (libev.EVFLAG_NOENV, 'noenv'),
+          (libev.EVFLAG_FORKCHECK, 'forkcheck'),
+          (libev.EVFLAG_SIGNALFD, 'signalfd'),
+          (libev.EVFLAG_NOSIGMASK, 'nosigmask')]
+
+_flags_str2int = dict((string, flag) for (flag, string) in _flags)
+
+_events = [(libev.EV_READ, 'READ'),
+           (libev.EV_WRITE, 'WRITE'),
+           (libev.EV__IOFDSET, '_IOFDSET'),
+           (libev.EV_PERIODIC, 'PERIODIC'),
+           (libev.EV_SIGNAL, 'SIGNAL'),
+           (libev.EV_CHILD, 'CHILD'),
+           (libev.EV_STAT, 'STAT'),
+           (libev.EV_IDLE, 'IDLE'),
+           (libev.EV_PREPARE, 'PREPARE'),
+           (libev.EV_CHECK, 'CHECK'),
+           (libev.EV_EMBED, 'EMBED'),
+           (libev.EV_FORK, 'FORK'),
+           (libev.EV_CLEANUP, 'CLEANUP'),
+           (libev.EV_ASYNC, 'ASYNC'),
+           (libev.EV_CUSTOM, 'CUSTOM'),
+           (libev.EV_ERROR, 'ERROR')]
+
+
+def _flags_to_list(flags):
+    result = []
+    for code, value in _flags:
+        if flags & code:
+            result.append(value)
+        flags &= ~code
+        if not flags:
+            break
+    if flags:
+        result.append(flags)
+    return result
+
+if sys.version_info[0] >= 3:
+    basestring = (bytes, str)
+    integer_types = (int,)
+else:
+    import __builtin__ # pylint:disable=import-error
+    basestring = __builtin__.basestring,
+    integer_types = (int, __builtin__.long)
+
+
+def _flags_to_int(flags):
+    # Note, that order does not matter, libev has its own predefined order
+    if not flags:
+        return 0
+    if isinstance(flags, integer_types):
+        return flags
+    result = 0
+    try:
+        if isinstance(flags, basestring):
+            flags = flags.split(',')
+        for value in flags:
+            value = value.strip().lower()
+            if value:
+                result |= _flags_str2int[value]
+    except KeyError as ex:
+        raise ValueError('Invalid backend or flag: %s\nPossible values: %s' % (ex, ', '.join(sorted(_flags_str2int.keys()))))
+    return result
+
+
+def _str_hex(flag):
+    if isinstance(flag, integer_types):
+        return hex(flag)
+    return str(flag)
+
+
+def _check_flags(flags):
+    as_list = []
+    flags &= libev.EVBACKEND_MASK
+    if not flags:
+        return
+    if not flags & libev.EVBACKEND_ALL:
+        raise ValueError('Invalid value for backend: 0x%x' % flags)
+    if not flags & libev.ev_supported_backends():
+        as_list = [_str_hex(x) for x in _flags_to_list(flags)]
+        raise ValueError('Unsupported backend: %s' % '|'.join(as_list))
+
+
+def _events_to_str(events):
+    result = []
+    for (flag, string) in _events:
+        c_flag = flag
+        if events & c_flag:
+            result.append(string)
+            events = events & (~c_flag)
+        if not events:
+            break
+    if events:
+        result.append(hex(events))
+    return '|'.join(result)
+
+
+def supported_backends():
+    return _flags_to_list(libev.ev_supported_backends())
+
+
+def recommended_backends():
+    return _flags_to_list(libev.ev_recommended_backends())
+
+
+def embeddable_backends():
+    return _flags_to_list(libev.ev_embeddable_backends())
+
+
+def time():
+    return libev.ev_time()
+
+_default_loop_destroyed = False
+
+
+def _loop_callback(*args, **kwargs):
+    return ffi.callback(*args, **kwargs)
+
+
+class loop(object):
+    # pylint:disable=too-many-public-methods
+
+    error_handler = None
+
+    def __init__(self, flags=None, default=None):
+        self._in_callback = False
+        self._callbacks = []
+
+        # self._check is a watcher that runs in each iteration of the
+        # mainloop, just after the blocking call
+        self._check = ffi.new("struct ev_check *")
+        self._check_callback_ffi = _loop_callback("void(*)(struct ev_loop *, void*, int)",
+                                                  self._check_callback,
+                                                  onerror=self._check_callback_handle_error)
+        libev.ev_check_init(self._check, self._check_callback_ffi)
+
+        # self._prepare is a watcher that runs in each iteration of the mainloop,
+        # just before the blocking call
+        self._prepare = ffi.new("struct ev_prepare *")
+        self._prepare_callback_ffi = _loop_callback("void(*)(struct ev_loop *, void*, int)",
+                                                    self._run_callbacks,
+                                                    onerror=self._check_callback_handle_error)
+        libev.ev_prepare_init(self._prepare, self._prepare_callback_ffi)
+
+        # A timer we start and stop on demand. If we have callbacks,
+        # too many to run in one iteration of _run_callbacks, we turn this
+        # on so as to have the next iteration of the run loop return to us
+        # as quickly as possible.
+        # TODO: There may be a more efficient way to do this using ev_timer_again;
+        # see the "ev_timer" section of the ev manpage (http://linux.die.net/man/3/ev)
+        self._timer0 = ffi.new("struct ev_timer *")
+        libev.ev_timer_init(self._timer0, libev.gevent_noop, 0.0, 0.0)
+
+        # TODO: We may be able to do something nicer and use the existing python_callback
+        # combined with onerror and the class check/timer/prepare to simplify things
+        # and unify our handling
+
+        c_flags = _flags_to_int(flags)
+        _check_flags(c_flags)
+        c_flags |= libev.EVFLAG_NOENV
+        c_flags |= libev.EVFLAG_FORKCHECK
+        if default is None:
+            default = True
+            if _default_loop_destroyed:
+                default = False
+        if default:
+            self._ptr = libev.gevent_ev_default_loop(c_flags)
+            if not self._ptr:
+                raise SystemError("ev_default_loop(%s) failed" % (c_flags, ))
+
+        else:
+            self._ptr = libev.ev_loop_new(c_flags)
+            if not self._ptr:
+                raise SystemError("ev_loop_new(%s) failed" % (c_flags, ))
+        if default or globals()["__SYSERR_CALLBACK"] is None:
+            set_syserr_cb(self._handle_syserr)
+
+        libev.ev_prepare_start(self._ptr, self._prepare)
+        self.unref()
+        libev.ev_check_start(self._ptr, self._check)
+        self.unref()
+
+        self._keepaliveset = set()
+
+    def _check_callback_handle_error(self, t, v, tb):
+        # None as the context argument causes the exception to be raised
+        # in the main greenlet.
+        self.handle_error(None, t, v, tb)
+
+    def _check_callback(self, *args):
+        # If we have the onerror callback, this is a no-op; all the real
+        # work to rethrow the exception is done by the onerror callback
+        pass
+
+    def _run_callbacks(self, _evloop, _, _revents):
+        count = 1000
+        libev.ev_timer_stop(self._ptr, self._timer0)
+        while self._callbacks and count > 0:
+            callbacks = self._callbacks
+            self._callbacks = []
+            for cb in callbacks:
+                self.unref()
+                callback = cb.callback
+                args = cb.args
+                if callback is None or args is None:
+                    # it's been stopped
+                    continue
+
+                cb.callback = None
+
+                try:
+                    callback(*args)
+                except: # pylint:disable=bare-except
+                    # If we allow an exception to escape this method (while we are running the ev callback),
+                    # then CFFI will print the error and libev will continue executing.
+                    # There are two problems with this. The first is that the code after
+                    # the loop won't run. The second is that any remaining callbacks scheduled
+                    # for this loop iteration will be silently dropped; they won't run, but they'll
+                    # also not be *stopped* (which is not a huge deal unless you're looking for
+                    # consistency or checking the boolean/pending status; the loop doesn't keep
+                    # a reference to them like it does to watchers...*UNLESS* the callback itself had
+                    # a reference to a watcher; then I don't know what would happen, it depends on
+                    # the state of the watcher---a leak or crash is not totally inconceivable).
+                    # The Cython implementation in core.ppyx uses gevent_call from callbacks.c
+                    # to run the callback, which uses gevent_handle_error to handle any errors the
+                    # Python callback raises...it unconditionally simply prints any error raised
+                    # by loop.handle_error and clears it, so callback handling continues.
+                    # We take a similar approach (but are extra careful about printing)
+                    try:
+                        self.handle_error(cb, *sys.exc_info())
+                    except: # pylint:disable=bare-except
+                        try:
+                            print("Exception while handling another error", file=sys.stderr)
+                            traceback.print_exc()
+                        except: # pylint:disable=bare-except
+                            pass # Nothing we can do here
+                finally:
+                    # NOTE: this must be reset here, because cb.args is used as a flag in
+                    # the callback class so that bool(cb) of a callback that has been run
+                    # becomes False
+                    cb.args = None
+                    count -= 1
+        if self._callbacks:
+            libev.ev_timer_start(self._ptr, self._timer0)
+
+    def _stop_aux_watchers(self):
+        if libev.ev_is_active(self._prepare):
+            self.ref()
+            libev.ev_prepare_stop(self._ptr, self._prepare)
+        if libev.ev_is_active(self._check):
+            self.ref()
+            libev.ev_check_stop(self._ptr, self._check)
+
+    def destroy(self):
+        global _default_loop_destroyed
+        if self._ptr:
+            self._stop_aux_watchers()
+            if globals()["__SYSERR_CALLBACK"] == self._handle_syserr:
+                set_syserr_cb(None)
+            if libev.ev_is_default_loop(self._ptr):
+                _default_loop_destroyed = True
+            libev.ev_loop_destroy(self._ptr)
+            self._ptr = ffi.NULL
+
+    @property
+    def ptr(self):
+        return self._ptr
+
+    @property
+    def WatcherType(self):
+        return watcher
+
+    @property
+    def MAXPRI(self):
+        return libev.EV_MAXPRI
+
+    @property
+    def MINPRI(self):
+        return libev.EV_MINPRI
+
+    def _handle_syserr(self, message, errno):
+        try:
+            errno = os.strerror(errno)
+        except: # pylint:disable=bare-except
+            traceback.print_exc()
+        try:
+            message = '%s: %s' % (message, errno)
+        except: # pylint:disable=bare-except
+            traceback.print_exc()
+        self.handle_error(None, SystemError, SystemError(message), None)
+
+    def handle_error(self, context, type, value, tb):
+        handle_error = None
+        error_handler = self.error_handler
+        if error_handler is not None:
+            # we do want to do getattr every time so that setting Hub.handle_error property just works
+            handle_error = getattr(error_handler, 'handle_error', error_handler)
+            handle_error(context, type, value, tb)
+        else:
+            self._default_handle_error(context, type, value, tb)
+
+    def _default_handle_error(self, context, type, value, tb): # pylint:disable=unused-argument
+        # note: Hub sets its own error handler so this is not used by gevent
+        # this is here to make core.loop usable without the rest of gevent
+        traceback.print_exception(type, value, tb)
+        libev.ev_break(self._ptr, libev.EVBREAK_ONE)
+
+    def run(self, nowait=False, once=False):
+        flags = 0
+        if nowait:
+            flags |= libev.EVRUN_NOWAIT
+        if once:
+            flags |= libev.EVRUN_ONCE
+
+        libev.ev_run(self._ptr, flags)
+
+    def reinit(self):
+        libev.ev_loop_fork(self._ptr)
+
+    def ref(self):
+        libev.ev_ref(self._ptr)
+
+    def unref(self):
+        libev.ev_unref(self._ptr)
+
+    def break_(self, how=libev.EVBREAK_ONE):
+        libev.ev_break(self._ptr, how)
+
+    def verify(self):
+        libev.ev_verify(self._ptr)
+
+    def now(self):
+        return libev.ev_now(self._ptr)
+
+    def update(self):
+        libev.ev_now_update(self._ptr)
+
+    def __repr__(self):
+        return '<%s at 0x%x %s>' % (self.__class__.__name__, id(self), self._format())
+
+    @property
+    def default(self):
+        return True if libev.ev_is_default_loop(self._ptr) else False
+
+    @property
+    def iteration(self):
+        return libev.ev_iteration(self._ptr)
+
+    @property
+    def depth(self):
+        return libev.ev_depth(self._ptr)
+
+    @property
+    def backend_int(self):
+        return libev.ev_backend(self._ptr)
+
+    @property
+    def backend(self):
+        backend = libev.ev_backend(self._ptr)
+        for key, value in _flags:
+            if key == backend:
+                return value
+        return backend
+
+    @property
+    def pendingcnt(self):
+        return libev.ev_pending_count(self._ptr)
+
+    def io(self, fd, events, ref=True, priority=None):
+        return io(self, fd, events, ref, priority)
+
+    def timer(self, after, repeat=0.0, ref=True, priority=None):
+        return timer(self, after, repeat, ref, priority)
+
+    def signal(self, signum, ref=True, priority=None):
+        return signal(self, signum, ref, priority)
+
+    def idle(self, ref=True, priority=None):
+        return idle(self, ref, priority)
+
+    def prepare(self, ref=True, priority=None):
+        return prepare(self, ref, priority)
+
+    def check(self, ref=True, priority=None):
+        return check(self, ref, priority)
+
+    def fork(self, ref=True, priority=None):
+        return fork(self, ref, priority)
+
+    def async(self, ref=True, priority=None):
+        return async(self, ref, priority)
+
+    if sys.platform != "win32":
+
+        def child(self, pid, trace=0, ref=True):
+            return child(self, pid, trace, ref)
+
+        def install_sigchld(self):
+            libev.gevent_install_sigchld_handler()
+
+        def reset_sigchld(self):
+            libev.gevent_reset_sigchld_handler()
+
+    def stat(self, path, interval=0.0, ref=True, priority=None):
+        return stat(self, path, interval, ref, priority)
+
+    def callback(self, priority=None):
+        return callback(self, priority)
+
+    def run_callback(self, func, *args):
+        cb = callback(func, args)
+        self._callbacks.append(cb)
+        self.ref()
+
+        return cb
+
+    def _format(self):
+        if not self._ptr:
+            return 'destroyed'
+        msg = self.backend
+        if self.default:
+            msg += ' default'
+        msg += ' pending=%s' % self.pendingcnt
+        msg += self._format_details()
+        return msg
+
+    def _format_details(self):
+        msg = ''
+        fileno = self.fileno()
+        try:
+            activecnt = self.activecnt
+        except AttributeError:
+            activecnt = None
+        if activecnt is not None:
+            msg += ' ref=' + repr(activecnt)
+        if fileno is not None:
+            msg += ' fileno=' + repr(fileno)
+        #if sigfd is not None and sigfd != -1:
+        #    msg += ' sigfd=' + repr(sigfd)
+        return msg
+
+    def fileno(self):
+        if self._ptr:
+            fd = self._ptr.backend_fd
+            if fd >= 0:
+                return fd
+
+    @property
+    def activecnt(self):
+        if not self._ptr:
+            raise ValueError('operation on destroyed loop')
+        return self._ptr.activecnt
+
+# For times when *args is captured but often not passed (empty),
+# we can avoid keeping the new tuple that was created for *args
+# around by using a constant.
+_NOARGS = ()
+
+
+class callback(object):
+
+    __slots__ = ('callback', 'args')
+
+    def __init__(self, callback, args):
+        self.callback = callback
+        self.args = args or _NOARGS
+
+    def stop(self):
+        self.callback = None
+        self.args = None
+
+    # Note that __nonzero__ and pending are different
+    # bool() is used in contexts where we need to know whether to schedule another callback,
+    # so it's true if it's pending or currently running
+    # 'pending' has the same meaning as libev watchers: it is cleared before actually
+    # running the callback
+
+    def __nonzero__(self):
+        # it's nonzero if it's pending or currently executing
+        # NOTE: This depends on loop._run_callbacks setting the args property
+        # to None.
+        return self.args is not None
+    __bool__ = __nonzero__
+
+    @property
+    def pending(self):
+        return self.callback is not None
+
+    def _format(self):
+        return ''
+
+    def __repr__(self):
+        result = "<%s at 0x%x" % (self.__class__.__name__, id(self))
+        if self.pending:
+            result += " pending"
+        if self.callback is not None:
+            result += " callback=%r" % (self.callback, )
+        if self.args is not None:
+            result += " args=%r" % (self.args, )
+        if self.callback is None and self.args is None:
+            result += " stopped"
+        return result + ">"
+
+
+class watcher(object):
+
+    def __init__(self, _loop, ref=True, priority=None, args=_NOARGS):
+        self.loop = _loop
+        if ref:
+            self._flags = 0
+        else:
+            self._flags = 4
+        self._args = None
+        self._callback = None
+        self._handle = ffi.new_handle(self)
+
+        self._watcher = ffi.new(self._watcher_struct_pointer_type)
+        self._watcher.data = self._handle
+        if priority is not None:
+            libev.ev_set_priority(self._watcher, priority)
+        self._watcher_init(self._watcher,
+                           self._watcher_callback,
+                           *args)
+
+    # A string identifying the type of libev object we watch, e.g., 'ev_io'
+    # This should be a class attribute.
+    _watcher_type = None
+    # A class attribute that is the callback on the libev object that init's the C struct,
+    # e.g., libev.ev_io_init. If None, will be set by _init_subclasses.
+    _watcher_init = None
+    # A class attribute that is the callback on the libev object that starts the C watcher,
+    # e.g., libev.ev_io_start. If None, will be set by _init_subclasses.
+    _watcher_start = None
+    # A class attribute that is the callback on the libev object that stops the C watcher,
+    # e.g., libev.ev_io_stop. If None, will be set by _init_subclasses.
+    _watcher_stop = None
+    # A cffi ctype object identifying the struct pointer we create.
+    # This is a class attribute set based on the _watcher_type
+    _watcher_struct_pointer_type = None
+    # The attribute of the libev object identifying the custom
+    # callback function for this type of watcher. This is a class
+    # attribute set based on the _watcher_type in _init_subclasses.
+    _watcher_callback = None
+
+    @classmethod
+    def _init_subclasses(cls):
+        for subclass in cls.__subclasses__(): # pylint:disable=no-member
+            watcher_type = subclass._watcher_type
+            subclass._watcher_struct_pointer_type = ffi.typeof('struct ' + watcher_type + '*')
+            subclass._watcher_callback = ffi.addressof(libev,
+                                                       '_gevent_generic_callback')
+            for name in 'start', 'stop', 'init':
+                ev_name = watcher_type + '_' + name
+                watcher_name = '_watcher' + '_' + name
+                if getattr(subclass, watcher_name) is None:
+                    setattr(subclass, watcher_name,
+                            getattr(libev, ev_name))
+
+    # this is not needed, since we keep alive the watcher while it's started
+    #def __del__(self):
+    #    self._watcher_stop(self.loop._ptr, self._watcher)
+
+    def __repr__(self):
+        formats = self._format()
+        result = "<%s at 0x%x%s" % (self.__class__.__name__, id(self), formats)
+        if self.pending:
+            result += " pending"
+        if self.callback is not None:
+            result += " callback=%r" % (self.callback, )
+        if self.args is not None:
+            result += " args=%r" % (self.args, )
+        if self.callback is None and self.args is None:
+            result += " stopped"
+        result += " handle=%s" % (self._watcher.data)
+        return result + ">"
+
+    def _format(self):
+        return ''
+
+    def _libev_unref(self):
+        if self._flags & 6 == 4:
+            self.loop.unref()
+            self._flags |= 2
+
+    def _get_ref(self):
+        return False if self._flags & 4 else True
+
+    def _set_ref(self, value):
+        if value:
+            if not self._flags & 4:
+                return  # ref is already True
+            if self._flags & 2:  # ev_unref was called, undo
+                self.loop.ref()
+            self._flags &= ~6  # do not want unref, no outstanding unref
+        else:
+            if self._flags & 4:
+                return  # ref is already False
+            self._flags |= 4
+            if not self._flags & 2 and libev.ev_is_active(self._watcher):
+                self.loop.unref()
+                self._flags |= 2
+
+    ref = property(_get_ref, _set_ref)
+
+    def _get_callback(self):
+        return self._callback
+
+    def _set_callback(self, cb):
+        if not callable(cb) and cb is not None:
+            raise TypeError("Expected callable, not %r" % (cb, ))
+        self._callback = cb
+    callback = property(_get_callback, _set_callback)
+
+    def _get_args(self):
+        return self._args
+
+    def _set_args(self, args):
+        if not isinstance(args, tuple) and args is not None:
+            raise TypeError("args must be a tuple or None")
+        self._args = args
+
+    args = property(_get_args, _set_args)
+
+    def start(self, callback, *args):
+        if callback is None:
+            raise TypeError('callback must be callable, not None')
+        self.callback = callback
+        self.args = args or _NOARGS
+        self._libev_unref()
+        self.loop._keepaliveset.add(self)
+        self._watcher_start(self.loop._ptr, self._watcher)
+
+    def stop(self):
+        if self._flags & 2:
+            self.loop.ref()
+            self._flags &= ~2
+        self._watcher_stop(self.loop._ptr, self._watcher)
+        self.loop._keepaliveset.discard(self)
+        self._callback = None
+        self.args = None
+
+    def _get_priority(self):
+        return libev.ev_priority(self._watcher)
+
+    def _set_priority(self, priority):
+        if libev.ev_is_active(self._watcher):
+            raise AttributeError("Cannot set priority of an active watcher")
+        libev.ev_set_priority(self._watcher, priority)
+
+    priority = property(_get_priority, _set_priority)
+
+    def feed(self, revents, callback, *args):
+        self.callback = callback
+        self.args = args or _NOARGS
+        if self._flags & 6 == 4:
+            self.loop.unref()
+            self._flags |= 2
+        libev.ev_feed_event(self.loop._ptr, self._watcher, revents)
+        if not self._flags & 1:
+            # Py_INCREF(<PyObjectPtr>self)
+            self._flags |= 1
+
+    @property
+    def active(self):
+        return True if libev.ev_is_active(self._watcher) else False
+
+    @property
+    def pending(self):
+        return True if libev.ev_is_pending(self._watcher) else False
+
+
+class io(watcher):
+    _watcher_type = 'ev_io'
+
+    def __init__(self, loop, fd, events, ref=True, priority=None):
+        # XXX: Win32: Need to vfd_open the fd and free the old one?
+        # XXX: Win32: Need a destructor to free the old fd?
+        if fd < 0:
+            raise ValueError('fd must be non-negative: %r' % fd)
+        if events & ~(libev.EV__IOFDSET | libev.EV_READ | libev.EV_WRITE):
+            raise ValueError('illegal event mask: %r' % events)
+        watcher.__init__(self, loop, ref=ref, priority=priority, args=(fd, events))
+
+    def start(self, callback, *args, **kwargs):
+        # pylint:disable=arguments-differ
+        args = args or _NOARGS
+        if kwargs.get('pass_events'):
+            args = (GEVENT_CORE_EVENTS, ) + args
+        watcher.start(self, callback, *args)
+
+    def _get_fd(self):
+        return vfd_get(self._watcher.fd)
+
+    def _set_fd(self, fd):
+        if libev.ev_is_active(self._watcher):
+            raise AttributeError("'io' watcher attribute 'fd' is read-only while watcher is active")
+        vfd = vfd_open(fd)
+        vfd_free(self._watcher.fd)
+        self._watcher_init(self._watcher, self._watcher_callback, vfd, self._watcher.events)
+
+    fd = property(_get_fd, _set_fd)
+
+    def _get_events(self):
+        return self._watcher.events
+
+    def _set_events(self, events):
+        if libev.ev_is_active(self._watcher):
+            raise AttributeError("'io' watcher attribute 'events' is read-only while watcher is active")
+        self._watcher_init(self._watcher, self._watcher_callback, self._watcher.fd, events)
+
+    events = property(_get_events, _set_events)
+
+    @property
+    def events_str(self):
+        return _events_to_str(self._watcher.events)
+
+    def _format(self):
+        return ' fd=%s events=%s' % (self.fd, self.events_str)
+
+
+class timer(watcher):
+    _watcher_type = 'ev_timer'
+
+    def __init__(self, loop, after=0.0, repeat=0.0, ref=True, priority=None):
+        if repeat < 0.0:
+            raise ValueError("repeat must be positive or zero: %r" % repeat)
+        watcher.__init__(self, loop, ref=ref, priority=priority, args=(after, repeat))
+
+    def start(self, callback, *args, **kw):
+        # pylint:disable=arguments-differ
+        update = kw.get("update", True)
+        if update:
+            # Quoth the libev doc: "This is a costly operation and is
+            # usually done automatically within ev_run(). This
+            # function is rarely useful, but when some event callback
+            # runs for a very long time without entering the event
+            # loop, updating libev's idea of the current time is a
+            # good idea."
+            # So do we really need to default to true?
+            libev.ev_now_update(self.loop._ptr)
+        watcher.start(self, callback, *args)
+
+    @property
+    def at(self):
+        return self._watcher.at
+
+    def again(self, callback, *args, **kw):
+        # Exactly the same as start(), just with a different initializer
+        # function
+        self._watcher_start = libev.ev_timer_again
+        try:
+            self.start(callback, *args, **kw)
+        finally:
+            del self._watcher_start
+
+
+class signal(watcher):
+    _watcher_type = 'ev_signal'
+
+    def __init__(self, loop, signalnum, ref=True, priority=None):
+        if signalnum < 1 or signalnum >= signalmodule.NSIG:
+            raise ValueError('illegal signal number: %r' % signalnum)
+        # still possible to crash on one of libev's asserts:
+        # 1) "libev: ev_signal_start called with illegal signal number"
+        #    EV_NSIG might be different from signal.NSIG on some platforms
+        # 2) "libev: a signal must not be attached to two different loops"
+        #    we probably could check that in LIBEV_EMBED mode, but not in general
+        watcher.__init__(self, loop, ref=ref, priority=priority, args=(signalnum, ))
+
+
+class idle(watcher):
+    _watcher_type = 'ev_idle'
+
+
+class prepare(watcher):
+    _watcher_type = 'ev_prepare'
+
+
+class check(watcher):
+    _watcher_type = 'ev_check'
+
+
+class fork(watcher):
+    _watcher_type = 'ev_fork'
+
+
+class async(watcher):
+    _watcher_type = 'ev_async'
+
+    def send(self):
+        libev.ev_async_send(self.loop._ptr, self._watcher)
+
+    @property
+    def pending(self):
+        return True if libev.ev_async_pending(self._watcher) else False
+
+
+class child(watcher):
+    _watcher_type = 'ev_child'
+
+    def __init__(self, loop, pid, trace=0, ref=True):
+        if not loop.default:
+            raise TypeError('child watchers are only available on the default loop')
+        loop.install_sigchld()
+        watcher.__init__(self, loop, ref=ref, args=(pid, trace))
+
+    def _format(self):
+        return ' pid=%r rstatus=%r' % (self.pid, self.rstatus)
+
+    @property
+    def pid(self):
+        return self._watcher.pid
+
+    @property
+    def rpid(self, ):
+        return self._watcher.rpid
+
+    @rpid.setter
+    def rpid(self, value):
+        self._watcher.rpid = value
+
+    @property
+    def rstatus(self):
+        return self._watcher.rstatus
+
+    @rstatus.setter
+    def rstatus(self, value):
+        self._watcher.rstatus = value
+
+
+class stat(watcher):
+    _watcher_type = 'ev_stat'
+
+    @staticmethod
+    def _encode_path(path):
+        if isinstance(path, bytes):
+            return path
+
+        # encode for the filesystem. Not all systems (e.g., Unix)
+        # will have an encoding specified
+        encoding = sys.getfilesystemencoding() or 'utf-8'
+        try:
+            path = path.encode(encoding, 'surrogateescape')
+        except LookupError:
+            # Can't encode it, and the error handler doesn't
+            # exist. Probably on Python 2 with an astral character.
+            # Not sure how to handle this.
+            raise UnicodeEncodeError("Can't encode path to filesystem encoding")
+        return path
+
+    def __init__(self, _loop, path, interval=0.0, ref=True, priority=None):
+        # Store the encoded path in the same attribute that corecext does
+        self._paths = self._encode_path(path)
+
+        # Keep the original path to avoid re-encoding, especially on Python 3
+        self._path = path
+
+        # Although CFFI would automatically convert a bytes object into a char* when
+        # calling ev_stat_init(..., char*, ...), on PyPy the char* pointer is not
+        # guaranteed to live past the function call. On CPython, only with a constant/interned
+        # bytes object is the pointer guaranteed to last path the function call. (And since
+        # Python 3 is pretty much guaranteed to produce a newly-encoded bytes object above, thats
+        # rarely the case). Therefore, we must keep a reference to the produced cdata object
+        # so that the struct ev_stat_watcher's `path` pointer doesn't become invalid/deallocated
+        self._cpath = ffi.new('char[]', self._paths)
+
+        watcher.__init__(self, _loop, ref=ref, priority=priority,
+                         args=(self._cpath,
+                               interval))
+
+    @property
+    def path(self):
+        return self._path
+
+    @property
+    def attr(self):
+        if not self._watcher.attr.st_nlink:
+            return
+        return self._watcher.attr
+
+    @property
+    def prev(self):
+        if not self._watcher.prev.st_nlink:
+            return
+        return self._watcher.prev
+
+    @property
+    def interval(self):
+        return self._watcher.interval
+
+# All watcher subclasses must be declared above. Now we do some
+# initialization; this is not only a minor optimization, it protects
+# against later runtime typos and attribute errors
+watcher._init_subclasses()
+
+
+def _syserr_cb(msg):
+    try:
+        msg = ffi.string(msg)
+        __SYSERR_CALLBACK(msg, ffi.errno)
+    except:
+        set_syserr_cb(None)
+        raise  # let cffi print the traceback
+
+_syserr_cb._cb = ffi.callback("void(*)(char *msg)", _syserr_cb)
+
+
+def set_syserr_cb(callback):
+    global __SYSERR_CALLBACK
+    if callback is None:
+        libev.ev_set_syserr_cb(ffi.NULL)
+        __SYSERR_CALLBACK = None
+    elif callable(callback):
+        libev.ev_set_syserr_cb(_syserr_cb._cb)
+        __SYSERR_CALLBACK = callback
+    else:
+        raise TypeError('Expected callable or None, got %r' % (callback, ))
+
+__SYSERR_CALLBACK = None
+
+LIBEV_EMBED = True