Mini Shell

# coding: utf-8
"""Python bindings for 0MQ."""

# Copyright (C) PyZMQ Developers
# Distributed under the terms of the Modified BSD License.

import atexit
import os
from threading import Lock
from weakref import WeakSet

from zmq.backend import Context as ContextBase
from . import constants
from .attrsettr import AttributeSetter
from .constants import ENOTSUP, LINGER, ctx_opt_names
from .socket import Socket
from zmq.error import ZMQError

# notice when exiting, to avoid triggering term on exit
_exiting = False
def _notice_atexit():
    global _exiting
    _exiting = True
atexit.register(_notice_atexit)

class Context(ContextBase, AttributeSetter):
    """Create a zmq Context

    A zmq Context creates sockets via its ``ctx.socket`` method.
    """
    sockopts = None
    _instance = None
    _instance_lock = Lock()
    _instance_pid = None
    _shadow = False
    _sockets = None

    def __init__(self, io_threads=1, **kwargs):
        super(Context, self).__init__(io_threads=io_threads, **kwargs)
        if kwargs.get('shadow', False):
            self._shadow = True
        else:
            self._shadow = False
        self.sockopts = {}
        self._sockets = WeakSet()

    def __del__(self):
        """deleting a Context should terminate it, without trying non-threadsafe destroy"""

        # Calling locals() here conceals issue #1167 on Windows CPython 3.5.4.
        locals()

        if not self._shadow and not _exiting:
            self.term()
    
    def __enter__(self):
        return self
    
    def __exit__(self, *args, **kwargs):
        self.term()
    
    def __copy__(self, memo=None):
        """Copying a Context creates a shadow copy"""
        return self.__class__.shadow(self.underlying)
    
    __deepcopy__ = __copy__
    
    @classmethod
    def shadow(cls, address):
        """Shadow an existing libzmq context
        
        address is the integer address of the libzmq context
        or an FFI pointer to it.
        
        .. versionadded:: 14.1
        """
        from zmq.utils.interop import cast_int_addr
        address = cast_int_addr(address)
        return cls(shadow=address)
    
    @classmethod
    def shadow_pyczmq(cls, ctx):
        """Shadow an existing pyczmq context
        
        ctx is the FFI `zctx_t *` pointer
        
        .. versionadded:: 14.1
        """
        from pyczmq import zctx
        from zmq.utils.interop import cast_int_addr
        
        underlying = zctx.underlying(ctx)
        address = cast_int_addr(underlying)
        return cls(shadow=address)

    # static method copied from tornado IOLoop.instance
    @classmethod
    def instance(cls, io_threads=1):
        """Returns a global Context instance.

        Most single-threaded applications have a single, global Context.
        Use this method instead of passing around Context instances
        throughout your code.

        A common pattern for classes that depend on Contexts is to use
        a default argument to enable programs with multiple Contexts
        but not require the argument for simpler applications::

            class MyClass(object):
                def __init__(self, context=None):
                    self.context = context or Context.instance()

        .. versionchanged:: 18.1

            When called in a subprocess after forking,
            a new global instance is created instead of inheriting
            a Context that won't work from the parent process.
        """
        if (
            cls._instance is None
            or cls._instance_pid != os.getpid()
            or cls._instance.closed
        ):
            with cls._instance_lock:
                if (
                    cls._instance is None
                    or cls._instance_pid != os.getpid()
                    or cls._instance.closed
                ):
                    cls._instance = cls(io_threads=io_threads)
                    cls._instance_pid = os.getpid()
        return cls._instance

    def term(self):
        """Close or terminate the context.

        Context termination is performed in the following steps:

        - Any blocking operations currently in progress on sockets open within context shall
          raise :class:`zmq.ContextTerminated`.
          With the exception of socket.close(), any further operations on sockets open within this context
          shall raise :class:`zmq.ContextTerminated`.
        - After interrupting all blocking calls, term shall block until the following conditions are satisfied:
            - All sockets open within context have been closed.
            - For each socket within context, all messages sent on the socket have either been
              physically transferred to a network peer,
              or the socket's linger period set with the zmq.LINGER socket option has expired.

        For further details regarding socket linger behaviour refer to libzmq documentation for ZMQ_LINGER.

        This can be called to close the context by hand. If this is not called,
        the context will automatically be closed when it is garbage collected.
        """
        return super(Context, self).term()

    #-------------------------------------------------------------------------
    # Hooks for ctxopt completion
    #-------------------------------------------------------------------------
    
    def __dir__(self):
        keys = dir(self.__class__)

        for collection in (
            ctx_opt_names,
        ):
            keys.extend(collection)
        return keys

    #-------------------------------------------------------------------------
    # Creating Sockets
    #-------------------------------------------------------------------------

    def _add_socket(self, socket):
        self._sockets.add(socket)

    def _rm_socket(self, socket):
        if self._sockets:
            self._sockets.discard(socket)

    def destroy(self, linger=None):
        """Close all sockets associated with this context and then terminate
        the context.

        .. warning::

            destroy involves calling ``zmq_close()``, which is **NOT** threadsafe.
            If there are active sockets in other threads, this must not be called.

        Parameters
        ----------

        linger : int, optional
            If specified, set LINGER on sockets prior to closing them.
        """
        if self.closed:
            return

        sockets = self._sockets
        self._sockets = WeakSet()
        for s in sockets:
            if s and not s.closed:
                if linger is not None:
                    s.setsockopt(LINGER, linger)
                s.close()

        self.term()

    @property
    def _socket_class(self):
        return Socket

    def socket(self, socket_type, **kwargs):
        """Create a Socket associated with this Context.

        Parameters
        ----------
        socket_type : int
            The socket type, which can be any of the 0MQ socket types:
            REQ, REP, PUB, SUB, PAIR, DEALER, ROUTER, PULL, PUSH, etc.

        kwargs:
            will be passed to the __init__ method of the socket class.
        """
        if self.closed:
            raise ZMQError(ENOTSUP)
        s = self._socket_class(self, socket_type, **kwargs)
        for opt, value in self.sockopts.items():
            try:
                s.setsockopt(opt, value)
            except ZMQError:
                # ignore ZMQErrors, which are likely for socket options
                # that do not apply to a particular socket type, e.g.
                # SUBSCRIBE for non-SUB sockets.
                pass
        self._add_socket(s)
        return s

    def setsockopt(self, opt, value):
        """set default socket options for new sockets created by this Context

        .. versionadded:: 13.0
        """
        self.sockopts[opt] = value

    def getsockopt(self, opt):
        """get default socket options for new sockets created by this Context

        .. versionadded:: 13.0
        """
        return self.sockopts[opt]
    
    def _set_attr_opt(self, name, opt, value):
        """set default sockopts as attributes"""
        if name in constants.ctx_opt_names:
            return self.set(opt, value)
        else:
            self.sockopts[opt] = value
    
    def _get_attr_opt(self, name, opt):
        """get default sockopts as attributes"""
        if name in constants.ctx_opt_names:
            return self.get(opt)
        else:
            if opt not in self.sockopts:
                raise AttributeError(name)
            else:
                return self.sockopts[opt]
    
    def __delattr__(self, key):
        """delete default sockopts as attributes"""
        key = key.upper()
        try:
            opt = getattr(constants, key)
        except AttributeError:
            raise AttributeError("no such socket option: %s" % key)
        else:
            if opt not in self.sockopts:
                raise AttributeError(key)
            else:
                del self.sockopts[opt]

__all__ = ['Context']