new generic secop client

new client intended as base class for all clients

- based on Ennos secop client in nicos ([WIP] provide secop client)
- self healing connection singletons
- extension for other than TCP is foreseen (by extending new uri schemes)
- extensible name mangling
- seperate rx and tx threads supporting events
- internal cache
- extensible error handling
- callback for unhandled messages
- callback for descriptive data change
- callback for node stat change (connected, disconnected)
- a short close down and reconnect without change in descriptive data
  does not disturb the client side

works with secop-gui (change follows), planned to be used for Frappy
internal secop proxy and as a replacement for secop.client.baseclient.Client
in the nicos secop device.

-> secop/client/baseclient.py to be removed after planned changes

moved secop/client/__init__.py to secop/client/console.py because secop.client
would be the natural place to put the new base class.

Change-Id: I1a7b1f1ded2221a8f9fcdd52f9cc7414e8fbe035
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22218
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/lib/asynconn.py

@@ -0,0 +1,140 @@
+#  -*- coding: utf-8 -*-
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+
+"""asynchonous connections
+
+generic class for byte oriented communication
+includes implementation for TCP connections
+"""
+
+import socket
+import time
+
+from secop.lib import parseHostPort, tcpSocket, closeSocket
+
+
+class ConnectionClosed(ConnectionError):
+    pass
+
+
+class AsynConn:
+    timeout = 1  # inter byte timeout
+    SCHEME_MAP = {}
+    connection = None  # is not None, if connected
+    defaultport = None
+
+    def __new__(cls, uri):
+        scheme = uri.split('://')[0]
+        iocls = cls.SCHEME_MAP.get(scheme, None)
+        if not iocls:
+            # try tcp, if scheme not given
+            try:
+                host_port = parseHostPort(uri, cls.defaultport)
+            except (ValueError, TypeError, AssertionError):
+                raise ValueError('invalid uri: %s' % uri)
+            iocls = cls.SCHEME_MAP['tcp']
+            uri = 'tcp://%s:%d' % host_port
+        return object.__new__(iocls)
+
+    def __init__(self, *args):
+        self._rxbuffer = b''
+
+    def __del__(self):
+        self.disconnect()
+
+    @classmethod
+    def register_scheme(cls, scheme):
+        cls.SCHEME_MAP[scheme] = cls
+
+    def disconnect(self):
+        raise NotImplementedError
+
+    def send(self, data):
+        """send data (bytes!)
+
+        tries to send all data"""
+        raise NotImplementedError
+
+    def recv(self):
+        """return bytes received within timeout
+
+        in contrast to socket.recv:
+        - returns b'' on timeout
+        - raises ConnectionClosed if the other end has disconnected
+        """
+        raise NotImplementedError
+
+    def readline(self, timeout=None):
+        """read one line
+
+        return either a complete line or None in case of timeout
+        the timeout argument may increase, but not decrease the default timeout
+        """
+        if timeout:
+            end = time.time() + timeout
+        while b'\n' not in self._rxbuffer:
+            data = self.recv()
+            if not data:
+                if timeout:
+                    if time.time() < end:
+                        continue
+                    raise TimeoutError('timeout in readline')
+                return None
+            self._rxbuffer += data
+        line, self._rxbuffer = self._rxbuffer.split(b'\n', 1)
+        return line
+
+    def writeline(self, line):
+        self.send(line + b'\n')
+
+
+class AsynTcp(AsynConn):
+    def __init__(self, uri):
+        super().__init__()
+        self.uri = uri
+        if uri.startswith('tcp://'):
+            # should be the case always
+            uri = uri[6:]
+        self.connection = tcpSocket(uri, self.defaultport, self.timeout)
+
+    def disconnect(self):
+        if self.connection:
+            closeSocket(self.connection)
+        self.connection = None
+
+    def send(self, data):
+        """send data (bytes!)"""
+        self.connection.sendall(data)
+
+    def recv(self):
+        """return bytes received within 1 sec"""
+        try:
+            data = self.connection.recv(8192)
+            if data:
+                return data
+        except socket.timeout:
+            # timeout while waiting
+            return b''
+        raise ConnectionClosed()  # marks end of connection
+
+AsynTcp.register_scheme('tcp')