Preview: reduction.py
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//lib64/python3.9/multiprocessing/reduction.py
#
# Module which deals with pickling of objects.
#
# multiprocessing/reduction.py
#
# Copyright (c) 2006-2008, R Oudkerk
# Licensed to PSF under a Contributor Agreement.
#
from abc import ABCMeta
import copyreg
import functools
import io
import os
import pickle
import socket
import sys
from . import context
__all__ = ['send_handle', 'recv_handle', 'ForkingPickler', 'register', 'dump']
HAVE_SEND_HANDLE = (sys.platform == 'win32' or
(hasattr(socket, 'CMSG_LEN') and
hasattr(socket, 'SCM_RIGHTS') and
hasattr(socket.socket, 'sendmsg')))
#
# Pickler subclass
#
class ForkingPickler(pickle.Pickler):
'''Pickler subclass used by multiprocessing.'''
_extra_reducers = {}
_copyreg_dispatch_table = copyreg.dispatch_table
def __init__(self, *args):
super().__init__(*args)
self.dispatch_table = self._copyreg_dispatch_table.copy()
self.dispatch_table.update(self._extra_reducers)
@classmethod
def register(cls, type, reduce):
'''Register a reduce function for a type.'''
cls._extra_reducers[type] = reduce
@classmethod
def dumps(cls, obj, protocol=None):
buf = io.BytesIO()
cls(buf, protocol).dump(obj)
return buf.getbuffer()
loads = pickle.loads
register = ForkingPickler.register
def dump(obj, file, protocol=None):
'''Replacement for pickle.dump() using ForkingPickler.'''
ForkingPickler(file, protocol).dump(obj)
#
# Platform specific definitions
#
if sys.platform == 'win32':
# Windows
__all__ += ['DupHandle', 'duplicate', 'steal_handle']
import _winapi
def duplicate(handle, target_process=None, inheritable=False,
*, source_process=None):
'''Duplicate a handle. (target_process is a handle not a pid!)'''
current_process = _winapi.GetCurrentProcess()
if source_process is None:
source_process = current_process
if target_process is None:
target_process = current_process
return _winapi.DuplicateHandle(
source_process, handle, target_process,
0, inheritable, _winapi.DUPLICATE_SAME_ACCESS)
def steal_handle(source_pid, handle):
'''Steal a handle from process identified by source_pid.'''
source_process_handle = _winapi.OpenProcess(
_winapi.PROCESS_DUP_HANDLE, False, source_pid)
try:
return _winapi.DuplicateHandle(
source_process_handle, handle,
_winapi.GetCurrentProcess(), 0, False,
_winapi.DUPLICATE_SAME_ACCESS | _winapi.DUPLICATE_CLOSE_SOURCE)
finally:
_winapi.CloseHandle(source_process_handle)
def send_handle(conn, handle, destination_pid):
'''Send a handle over a local connection.'''
dh = DupHandle(handle, _winapi.DUPLICATE_SAME_ACCESS, destination_pid)
conn.send(dh)
def recv_handle(conn):
'''Receive a handle over a local connection.'''
return conn.recv().detach()
class DupHandle(object):
'''Picklable wrapper for a handle.'''
def __init__(self, handle, access, pid=None):
if pid is None:
# We just duplicate the handle in the current process and
# let the receiving process steal the handle.
pid = os.getpid()
proc = _winapi.OpenProcess(_winapi.PROCESS_DUP_HANDLE, False, pid)
try:
self._handle = _winapi.DuplicateHandle(
_winapi.GetCurrentProcess(),
handle, proc, access, False, 0)
finally:
_winapi.CloseHandle(proc)
self._access = access
self._pid = pid
def detach(self):
'''Get the handle. This should only be called once.'''
# retrieve handle from process which currently owns it
if self._pid == os.getpid():
# The handle has already been duplicated for this process.
return self._handle
# We must steal the handle from the process whose pid is self._pid.
proc = _winapi.OpenProcess(_winapi.PROCESS_DUP_HANDLE, False,
self._pid)
try:
return _winapi.DuplicateHandle(
proc, self._handle, _winapi.GetCurrentProcess(),
self._access, False, _winapi.DUPLICATE_CLOSE_SOURCE)
finally:
_winapi.CloseHandle(proc)
else:
# Unix
__all__ += ['DupFd', 'sendfds', 'recvfds']
import array
# On MacOSX we should acknowledge receipt of fds -- see Issue14669
ACKNOWLEDGE = sys.platform == 'darwin'
def sendfds(sock, fds):
'''Send an array of fds over an AF_UNIX socket.'''
fds = array.array('i', fds)
msg = bytes([len(fds) % 256])
sock.sendmsg([msg], [(socket.SOL_SOCKET, socket.SCM_RIGHTS, fds)])
if ACKNOWLEDGE and sock.recv(1) != b'A':
raise RuntimeError('did not receive acknowledgement of fd')
def recvfds(sock, size):
'''Receive an array of fds over an AF_UNIX socket.'''
a = array.array('i')
bytes_size = a.itemsize * size
msg, ancdata, flags, addr = sock.recvmsg(1, socket.CMSG_SPACE(bytes_size))
if not msg and not ancdata:
raise EOFError
try:
if ACKNOWLEDGE:
sock.send(b'A')
if len(ancdata) != 1:
raise RuntimeError('received %d items of ancdata' %
len(ancdata))
cmsg_level, cmsg_type, cmsg_data = ancdata[0]
if (cmsg_level == socket.SOL_SOCKET and
cmsg_type == socket.SCM_RIGHTS):
if len(cmsg_data) % a.itemsize != 0:
raise ValueError
a.frombytes(cmsg_data)
if len(a) % 256 != msg[0]:
raise AssertionError(
"Len is {0:n} but msg[0] is {1!r}".format(
len(a), msg[0]))
return list(a)
except (ValueError, IndexError):
pass
raise RuntimeError('Invalid data received')
def send_handle(conn, handle, destination_pid):
'''Send a handle over a local connection.'''
with socket.fromfd(conn.fileno(), socket.AF_UNIX, socket.SOCK_STREAM) as s:
sendfds(s, [handle])
def recv_handle(conn):
'''Receive a handle over a local connection.'''
with socket.fromfd(conn.fileno(), socket.AF_UNIX, socket.SOCK_STREAM) as s:
return recvfds(s, 1)[0]
def DupFd(fd):
'''Return a wrapper for an fd.'''
popen_obj = context.get_spawning_popen()
if popen_obj is not None:
return popen_obj.DupFd(popen_obj.duplicate_for_child(fd))
elif HAVE_SEND_HANDLE:
from . import resource_sharer
return resource_sharer.DupFd(fd)
else:
raise ValueError('SCM_RIGHTS appears not to be available')
#
# Try making some callable types picklable
#
def _reduce_method(m):
if m.__self__ is None:
return getattr, (m.__class__, m.__func__.__name__)
else:
return getattr, (m.__self__, m.__func__.__name__)
class _C:
def f(self):
pass
register(type(_C().f), _reduce_method)
def _reduce_method_descriptor(m):
return getattr, (m.__objclass__, m.__name__)
register(type(list.append), _reduce_method_descriptor)
register(type(int.__add__), _reduce_method_descriptor)
def _reduce_partial(p):
return _rebuild_partial, (p.func, p.args, p.keywords or {})
def _rebuild_partial(func, args, keywords):
return functools.partial(func, *args, **keywords)
register(functools.partial, _reduce_partial)
#
# Make sockets picklable
#
if sys.platform == 'win32':
def _reduce_socket(s):
from .resource_sharer import DupSocket
return _rebuild_socket, (DupSocket(s),)
def _rebuild_socket(ds):
return ds.detach()
register(socket.socket, _reduce_socket)
else:
def _reduce_socket(s):
df = DupFd(s.fileno())
return _rebuild_socket, (df, s.family, s.type, s.proto)
def _rebuild_socket(df, family, type, proto):
fd = df.detach()
return socket.socket(family, type, proto, fileno=fd)
register(socket.socket, _reduce_socket)
class AbstractReducer(metaclass=ABCMeta):
'''Abstract base class for use in implementing a Reduction class
suitable for use in replacing the standard reduction mechanism
used in multiprocessing.'''
ForkingPickler = ForkingPickler
register = register
dump = dump
send_handle = send_handle
recv_handle = recv_handle
if sys.platform == 'win32':
steal_handle = steal_handle
duplicate = duplicate
DupHandle = DupHandle
else:
sendfds = sendfds
recvfds = recvfds
DupFd = DupFd
_reduce_method = _reduce_method
_reduce_method_descriptor = _reduce_method_descriptor
_rebuild_partial = _rebuild_partial
_reduce_socket = _reduce_socket
_rebuild_socket = _rebuild_socket
def __init__(self, *args):
register(type(_C().f), _reduce_method)
register(type(list.append), _reduce_method_descriptor)
register(type(int.__add__), _reduce_method_descriptor)
register(functools.partial, _reduce_partial)
register(socket.socket, _reduce_socket)
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