[ADD] async modules wip

opcua/common/async_connection.py

+
+import asyncio
+import logging
+from opcua.common.connection import SecureConnection
+from opcua.ua.async_ua_binary import header_from_binary
+from opcua import ua
+
+logger = logging.getLogger('opcua.uaprotocol')
+
+
+class AsyncSecureConnection(SecureConnection):
+    """
+    Async version of SecureConnection
+    """
+
+    async def receive_from_socket(self, protocol):
+        """
+        Convert binary stream to OPC UA TCP message (see OPC UA
+        specs Part 6, 7.1: Hello, Acknowledge or ErrorMessage), or a Message
+        object, or None (if intermediate chunk is received)
+        """
+        logger.debug("Waiting for header")
+        header = await header_from_binary(protocol)
+        logger.info("received header: %s", header)
+        body = await protocol.read(header.body_size)
+        if len(body) != header.body_size:
+            # ToDo: should never happen since UASocketProtocol.read() waits until `size` bytes are received. Remove?
+            raise ua.UaError("{0} bytes expected, {1} available".format(header.body_size, len(body)))
+        return self.receive_from_header_and_body(header, ua.utils.Buffer(body))

opcua/ua/async_ua_binary.py

+
+import struct
+from opcua import ua
+from opcua.ua.ua_binary import Primitives
+
+
+async def header_from_binary(data):
+    hdr = ua.Header()
+    hdr.MessageType, hdr.ChunkType, hdr.packet_size = struct.unpack("<3scI", await data.read(8))
+    hdr.body_size = hdr.packet_size - 8
+    if hdr.MessageType in (ua.MessageType.SecureOpen, ua.MessageType.SecureClose, ua.MessageType.SecureMessage):
+        hdr.body_size -= 4
+        hdr.ChannelId = Primitives.UInt32.unpack(ua.utils.Buffer(await data.read(4)))
+    return hdr