Archipelago » qemu

# QEMU Monitor Protocol Python class

# 

# Copyright (C) 2009, 2010 Red Hat Inc.

#

# Authors:

#  Luiz Capitulino <lcapitulino@redhat.com>

#

# This work is licensed under the terms of the GNU GPL, version 2.  See

# the COPYING file in the top-level directory.

import json

import errno

import socket

class QMPError(Exception):

    pass

class QMPConnectError(QMPError):

    pass

class QMPCapabilitiesError(QMPError):

    pass

class QEMUMonitorProtocol:

    def __init__(self, address):

        """

        Create a QEMUMonitorProtocol class.

        @param address: QEMU address, can be either a unix socket path (string)

                        or a tuple in the form ( address, port ) for a TCP

                        connection

        @note No connection is established, this is done by the connect() method

        """

        self.__events = []

        self.__address = address

        self.__sock = self.__get_sock()

        self.__sockfile = self.__sock.makefile()

    def __get_sock(self):

        if isinstance(self.__address, tuple):

            family = socket.AF_INET

        else:

            family = socket.AF_UNIX

        return socket.socket(family, socket.SOCK_STREAM)

    def __json_read(self, only_event=False):

        while True:

            data = self.__sockfile.readline()

            if not data:

                return

            resp = json.loads(data)

            if 'event' in resp:

                self.__events.append(resp)

                if not only_event:

                    continue

            return resp

    error = socket.error

    def connect(self):

        """

        Connect to the QMP Monitor and perform capabilities negotiation.

        @return QMP greeting dict

        @raise socket.error on socket connection errors

        @raise QMPConnectError if the greeting is not received

        @raise QMPCapabilitiesError if fails to negotiate capabilities

        """

        self.__sock.connect(self.__address)

        greeting = self.__json_read()

        if greeting is None or not greeting.has_key('QMP'):

            raise QMPConnectError

        # Greeting seems ok, negotiate capabilities

        resp = self.cmd('qmp_capabilities')

        if "return" in resp:

            return greeting

        raise QMPCapabilitiesError

    def cmd_obj(self, qmp_cmd):

        """

        Send a QMP command to the QMP Monitor.

        @param qmp_cmd: QMP command to be sent as a Python dict

        @return QMP response as a Python dict or None if the connection has

                been closed

        """

        try:

            self.__sock.sendall(json.dumps(qmp_cmd))

        except socket.error, err:

            if err[0] == errno.EPIPE:

                return

            raise socket.error(err)

        return self.__json_read()

    def cmd(self, name, args=None, id=None):

        """

        Build a QMP command and send it to the QMP Monitor.

        @param name: command name (string)

        @param args: command arguments (dict)

        @param id: command id (dict, list, string or int)

        """

        qmp_cmd = { 'execute': name }

        if args:

            qmp_cmd['arguments'] = args

        if id:

            qmp_cmd['id'] = id

        return self.cmd_obj(qmp_cmd)

    def get_events(self, wait=False):

        """

        Get a list of available QMP events.

        @param wait: block until an event is available (bool)

        """

        self.__sock.setblocking(0)

        try:

            self.__json_read()

        except socket.error, err:

            if err[0] == errno.EAGAIN:

                # No data available

                pass

        self.__sock.setblocking(1)

        if not self.__events and wait:

            self.__json_read(only_event=True)

        return self.__events

    def clear_events(self):

        """

        Clear current list of pending events.

        """

        self.__events = []

    def close(self):

        self.__sock.close()

        self.__sockfile.close()