256 lines
8.1 KiB
Python
256 lines
8.1 KiB
Python
# QEMU Monitor Protocol Python class
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#
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# Copyright (C) 2009, 2010 Red Hat Inc.
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#
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# Authors:
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# Luiz Capitulino <lcapitulino@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2. See
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# the COPYING file in the top-level directory.
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import json
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import errno
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import socket
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import logging
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class QMPError(Exception):
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pass
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class QMPConnectError(QMPError):
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pass
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class QMPCapabilitiesError(QMPError):
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pass
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class QMPTimeoutError(QMPError):
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pass
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class QEMUMonitorProtocol(object):
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#: Logger object for debugging messages
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logger = logging.getLogger('QMP')
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#: Socket's error class
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error = socket.error
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#: Socket's timeout
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timeout = socket.timeout
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def __init__(self, address, server=False):
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"""
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Create a QEMUMonitorProtocol class.
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@param address: QEMU address, can be either a unix socket path (string)
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or a tuple in the form ( address, port ) for a TCP
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connection
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@param server: server mode listens on the socket (bool)
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@raise socket.error on socket connection errors
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@note No connection is established, this is done by the connect() or
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accept() methods
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"""
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self.__events = []
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self.__address = address
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self.__sock = self.__get_sock()
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self.__sockfile = None
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if server:
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self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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self.__sock.bind(self.__address)
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self.__sock.listen(1)
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def __get_sock(self):
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if isinstance(self.__address, tuple):
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family = socket.AF_INET
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else:
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family = socket.AF_UNIX
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return socket.socket(family, socket.SOCK_STREAM)
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def __negotiate_capabilities(self):
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greeting = self.__json_read()
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if greeting is None or "QMP" not in greeting:
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raise QMPConnectError
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# Greeting seems ok, negotiate capabilities
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resp = self.cmd('qmp_capabilities')
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if "return" in resp:
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return greeting
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raise QMPCapabilitiesError
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def __json_read(self, only_event=False):
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while True:
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data = self.__sockfile.readline()
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if not data:
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return
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resp = json.loads(data)
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if 'event' in resp:
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self.logger.debug("<<< %s", resp)
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self.__events.append(resp)
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if not only_event:
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continue
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return resp
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def __get_events(self, wait=False):
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"""
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Check for new events in the stream and cache them in __events.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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"""
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# Check for new events regardless and pull them into the cache:
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self.__sock.setblocking(0)
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try:
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self.__json_read()
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except socket.error as err:
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if err[0] == errno.EAGAIN:
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# No data available
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pass
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self.__sock.setblocking(1)
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# Wait for new events, if needed.
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# if wait is 0.0, this means "no wait" and is also implicitly false.
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if not self.__events and wait:
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if isinstance(wait, float):
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self.__sock.settimeout(wait)
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try:
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ret = self.__json_read(only_event=True)
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except socket.timeout:
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raise QMPTimeoutError("Timeout waiting for event")
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except:
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raise QMPConnectError("Error while reading from socket")
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if ret is None:
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raise QMPConnectError("Error while reading from socket")
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self.__sock.settimeout(None)
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def connect(self, negotiate=True):
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"""
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Connect to the QMP Monitor and perform capabilities negotiation.
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@return QMP greeting dict
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@raise socket.error on socket connection errors
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@raise QMPConnectError if the greeting is not received
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@raise QMPCapabilitiesError if fails to negotiate capabilities
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"""
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self.__sock.connect(self.__address)
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self.__sockfile = self.__sock.makefile()
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if negotiate:
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return self.__negotiate_capabilities()
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def accept(self):
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"""
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Await connection from QMP Monitor and perform capabilities negotiation.
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@return QMP greeting dict
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@raise socket.error on socket connection errors
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@raise QMPConnectError if the greeting is not received
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@raise QMPCapabilitiesError if fails to negotiate capabilities
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"""
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self.__sock.settimeout(15)
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self.__sock, _ = self.__sock.accept()
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self.__sockfile = self.__sock.makefile()
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return self.__negotiate_capabilities()
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def cmd_obj(self, qmp_cmd):
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"""
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Send a QMP command to the QMP Monitor.
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@param qmp_cmd: QMP command to be sent as a Python dict
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@return QMP response as a Python dict or None if the connection has
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been closed
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"""
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self.logger.debug(">>> %s", qmp_cmd)
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try:
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self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
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except socket.error as err:
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if err[0] == errno.EPIPE:
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return
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raise socket.error(err)
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resp = self.__json_read()
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self.logger.debug("<<< %s", resp)
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return resp
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def cmd(self, name, args=None, cmd_id=None):
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"""
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Build a QMP command and send it to the QMP Monitor.
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@param name: command name (string)
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@param args: command arguments (dict)
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@param cmd_id: command id (dict, list, string or int)
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"""
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qmp_cmd = {'execute': name}
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if args:
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qmp_cmd['arguments'] = args
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if cmd_id:
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qmp_cmd['id'] = cmd_id
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return self.cmd_obj(qmp_cmd)
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def command(self, cmd, **kwds):
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"""
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Build and send a QMP command to the monitor, report errors if any
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"""
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ret = self.cmd(cmd, kwds)
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if "error" in ret:
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raise Exception(ret['error']['desc'])
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return ret['return']
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def pull_event(self, wait=False):
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"""
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Pulls a single event.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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@return The first available QMP event, or None.
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"""
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self.__get_events(wait)
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if self.__events:
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return self.__events.pop(0)
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return None
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def get_events(self, wait=False):
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"""
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Get a list of available QMP events.
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@param wait (bool): block until an event is available.
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@param wait (float): If wait is a float, treat it as a timeout value.
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@raise QMPTimeoutError: If a timeout float is provided and the timeout
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period elapses.
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@raise QMPConnectError: If wait is True but no events could be
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retrieved or if some other error occurred.
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@return The list of available QMP events.
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"""
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self.__get_events(wait)
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return self.__events
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def clear_events(self):
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"""
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Clear current list of pending events.
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"""
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self.__events = []
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def close(self):
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self.__sock.close()
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self.__sockfile.close()
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def settimeout(self, timeout):
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self.__sock.settimeout(timeout)
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def get_sock_fd(self):
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return self.__sock.fileno()
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def is_scm_available(self):
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return self.__sock.family == socket.AF_UNIX
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