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>

python/qemu/qtest.py

@@ -0,0 +1,116 @@
+# QEMU qtest library
+#
+# Copyright (C) 2015 Red Hat Inc.
+#
+# Authors:
+#  Fam Zheng <famz@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2.  See
+# the COPYING file in the top-level directory.
+#
+# Based on qmp.py.
+#
+
+import socket
+import os
+
+from . import QEMUMachine
+
+
+class QEMUQtestProtocol(object):
+    def __init__(self, address, server=False):
+        """
+        Create a QEMUQtestProtocol object.
+
+        @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._address = address
+        self._sock = self._get_sock()
+        self._sockfile = None
+        if server:
+            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 connect(self):
+        """
+        Connect to the qtest socket.
+
+        @raise socket.error on socket connection errors
+        """
+        self._sock.connect(self._address)
+        self._sockfile = self._sock.makefile()
+
+    def accept(self):
+        """
+        Await connection from QEMU.
+
+        @raise socket.error on socket connection errors
+        """
+        self._sock, _ = self._sock.accept()
+        self._sockfile = self._sock.makefile()
+
+    def cmd(self, qtest_cmd):
+        """
+        Send a qtest command on the wire.
+
+        @param qtest_cmd: qtest command text to be sent
+        """
+        self._sock.sendall((qtest_cmd + "\n").encode('utf-8'))
+        resp = self._sockfile.readline()
+        return resp
+
+    def close(self):
+        self._sock.close()
+        self._sockfile.close()
+
+    def settimeout(self, timeout):
+        self._sock.settimeout(timeout)
+
+
+class QEMUQtestMachine(QEMUMachine):
+    '''A QEMU VM'''
+
+    def __init__(self, binary, args=None, name=None, test_dir="/var/tmp",
+                 socket_scm_helper=None):
+        if name is None:
+            name = "qemu-%d" % os.getpid()
+        super(QEMUQtestMachine,
+              self).__init__(binary, args, name=name, test_dir=test_dir,
+                             socket_scm_helper=socket_scm_helper)
+        self._qtest = None
+        self._qtest_path = os.path.join(test_dir, name + "-qtest.sock")
+
+    def _base_args(self):
+        args = super(QEMUQtestMachine, self)._base_args()
+        args.extend(['-qtest', 'unix:path=' + self._qtest_path,
+                     '-machine', 'accel=qtest'])
+        return args
+
+    def _pre_launch(self):
+        super(QEMUQtestMachine, self)._pre_launch()
+        self._qtest = QEMUQtestProtocol(self._qtest_path, server=True)
+
+    def _post_launch(self):
+        super(QEMUQtestMachine, self)._post_launch()
+        self._qtest.accept()
+
+    def _post_shutdown(self):
+        super(QEMUQtestMachine, self)._post_shutdown()
+        self._remove_if_exists(self._qtest_path)
+
+    def qtest(self, cmd):
+        '''Send a qtest command to guest'''
+        return self._qtest.cmd(cmd)