Introduce a Python module structure

This is a simple move of Python code that wraps common QEMU
functionality, and are used by a number of different tests
and scripts.

By treating that code as a real Python module, we can more easily:
 * reuse code
 * have a proper place for the module's own unittests
 * apply a more consistent style
 * generate documentation

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Caio Carrara <ccarrara@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20190206162901.19082-2-crosa@redhat.com>
Signed-off-by: Cleber Rosa <crosa@redhat.com>

1 files changed, 256 insertions, 0 deletions

diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
new file mode 100644
index 0000000..5c8cf6a
--- /dev/null
+++ b/python/qemu/qmp.py
@@ -0,0 +1,256 @@
+# 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
+import logging
+
+
+class QMPError(Exception):
+    pass
+
+
+class QMPConnectError(QMPError):
+    pass
+
+
+class QMPCapabilitiesError(QMPError):
+    pass
+
+
+class QMPTimeoutError(QMPError):
+    pass
+
+
+class QEMUMonitorProtocol(object):
+
+    #: Logger object for debugging messages
+    logger = logging.getLogger('QMP')
+    #: Socket's error class
+    error = socket.error
+    #: Socket's timeout
+    timeout = socket.timeout
+
+    def __init__(self, address, server=False):
+        """
+        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
+        @param server: server mode listens on the socket (bool)
+        @raise socket.error on socket connection errors
+        @note No connection is established, this is done by the connect() or
+              accept() methods
+        """
+        self.__events = []
+        self.__address = address
+        self.__sock = self.__get_sock()
+        self.__sockfile = None
+        if server:
+            self.__sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            self.__sock.bind(self.__address)
+            self.__sock.listen(1)
+
+    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 __negotiate_capabilities(self):
+        greeting = self.__json_read()
+        if greeting is None or "QMP" not in greeting:
+            raise QMPConnectError
+        # Greeting seems ok, negotiate capabilities
+        resp = self.cmd('qmp_capabilities')
+        if "return" in resp:
+            return greeting
+        raise QMPCapabilitiesError
+
+    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.logger.debug("<<< %s", resp)
+                self.__events.append(resp)
+                if not only_event:
+                    continue
+            return resp
+
+    def __get_events(self, wait=False):
+        """
+        Check for new events in the stream and cache them in __events.
+
+        @param wait (bool): block until an event is available.
+        @param wait (float): If wait is a float, treat it as a timeout value.
+
+        @raise QMPTimeoutError: If a timeout float is provided and the timeout
+                                period elapses.
+        @raise QMPConnectError: If wait is True but no events could be
+                                retrieved or if some other error occurred.
+        """
+
+        # Check for new events regardless and pull them into the cache:
+        self.__sock.setblocking(0)
+        try:
+            self.__json_read()
+        except socket.error as err:
+            if err[0] == errno.EAGAIN:
+                # No data available
+                pass
+        self.__sock.setblocking(1)
+
+        # Wait for new events, if needed.
+        # if wait is 0.0, this means "no wait" and is also implicitly false.
+        if not self.__events and wait:
+            if isinstance(wait, float):
+                self.__sock.settimeout(wait)
+            try:
+                ret = self.__json_read(only_event=True)
+            except socket.timeout:
+                raise QMPTimeoutError("Timeout waiting for event")
+            except:
+                raise QMPConnectError("Error while reading from socket")
+            if ret is None:
+                raise QMPConnectError("Error while reading from socket")
+            self.__sock.settimeout(None)
+
+    def connect(self, negotiate=True):
+        """
+        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)
+        self.__sockfile = self.__sock.makefile()
+        if negotiate:
+            return self.__negotiate_capabilities()
+
+    def accept(self):
+        """
+        Await connection from 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.settimeout(15)
+        self.__sock, _ = self.__sock.accept()
+        self.__sockfile = self.__sock.makefile()
+        return self.__negotiate_capabilities()
+
+    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
+        """
+        self.logger.debug(">>> %s", qmp_cmd)
+        try:
+            self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
+        except socket.error as err:
+            if err[0] == errno.EPIPE:
+                return
+            raise socket.error(err)
+        resp = self.__json_read()
+        self.logger.debug("<<< %s", resp)
+        return resp
+
+    def cmd(self, name, args=None, cmd_id=None):
+        """
+        Build a QMP command and send it to the QMP Monitor.
+
+        @param name: command name (string)
+        @param args: command arguments (dict)
+        @param cmd_id: command id (dict, list, string or int)
+        """
+        qmp_cmd = {'execute': name}
+        if args:
+            qmp_cmd['arguments'] = args
+        if cmd_id:
+            qmp_cmd['id'] = cmd_id
+        return self.cmd_obj(qmp_cmd)
+
+    def command(self, cmd, **kwds):
+        """
+        Build and send a QMP command to the monitor, report errors if any
+        """
+        ret = self.cmd(cmd, kwds)
+        if "error" in ret:
+            raise Exception(ret['error']['desc'])
+        return ret['return']
+
+    def pull_event(self, wait=False):
+        """
+        Pulls a single event.
+
+        @param wait (bool): block until an event is available.
+        @param wait (float): If wait is a float, treat it as a timeout value.
+
+        @raise QMPTimeoutError: If a timeout float is provided and the timeout
+                                period elapses.
+        @raise QMPConnectError: If wait is True but no events could be
+                                retrieved or if some other error occurred.
+
+        @return The first available QMP event, or None.
+        """
+        self.__get_events(wait)
+
+        if self.__events:
+            return self.__events.pop(0)
+        return None
+
+    def get_events(self, wait=False):
+        """
+        Get a list of available QMP events.
+
+        @param wait (bool): block until an event is available.
+        @param wait (float): If wait is a float, treat it as a timeout value.
+
+        @raise QMPTimeoutError: If a timeout float is provided and the timeout
+                                period elapses.
+        @raise QMPConnectError: If wait is True but no events could be
+                                retrieved or if some other error occurred.
+
+        @return The list of available QMP events.
+        """
+        self.__get_events(wait)
+        return self.__events
+
+    def clear_events(self):
+        """
+        Clear current list of pending events.
+        """
+        self.__events = []
+
+    def close(self):
+        self.__sock.close()
+        self.__sockfile.close()
+
+    def settimeout(self, timeout):
+        self.__sock.settimeout(timeout)
+
+    def get_sock_fd(self):
+        return self.__sock.fileno()
+
+    def is_scm_available(self):
+        return self.__sock.family == socket.AF_UNIX