#
# 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, abstractmethod
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):
        '''Duplicate a handle.  (target_process is a handle not a pid!)'''
        if target_process is None:
            target_process = _winapi.GetCurrentProcess()
        return _winapi.DuplicateHandle(
            _winapi.GetCurrentProcess(), 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: