Async: remove length at the beginning of RPC messages.

This fix a nasty bug that would have been triggered by having
a JSON length that contains the bytes '\r\n', which are used for
message termination. Fortunately our messages are always short
enough that, to my knowledge, this bug has never been triggered.

cms/async/AsyncLibrary.py

@@ -38,7 +38,7 @@
 
 from cms.async import ServiceCoord, Address, get_service_address
 from cms.async.Utils import random_string, Logger, \
-     encode_length, encode_json, decode_length, decode_json
+     encode_json, decode_json
 
 
 # Our logger object - can be a standard one (provided in Utils), or a
@@ -526,12 +526,7 @@ def found_terminator(self):
 
         # We decode the arriving data
         try:
-            json_length = decode_length(data[:4])
-            if len(data) != json_length + 4:
-                logger.warning("Incoming message with binary data aren't "
-                               "supported anymore, discarding.")
-                return
-            message = decode_json(data[4:json_length + 4])
+            message = decode_json(data)
         except:
             logger.warning("Cannot understand incoming message, discarding.")
             return
@@ -596,12 +591,11 @@ def send_reply(self, response, method_response):
         try:
             response["__data"] = method_response
             json_message = encode_json(response)
-            json_length = encode_length(len(json_message))
         except ValueError as error:
             logger.warning("Cannot send response because of " +
                            "encoding error. %s" % repr(error))
             return
-        self._push_right(json_length + json_message)
+        self._push_right(json_message)
 
     def execute_rpc(self, method, data, callback=None, plus=None,
                     timeout=None):
@@ -678,13 +672,12 @@ def callback(self, data, error=None):
         # We encode the request and send it
         try:
             json_message = encode_json(message)
-            json_length = encode_length(len(json_message))
         except ValueError:
             msg = "Cannot send request of method %s because of " \
                 "encoding error." % method
             request.complete({"__error": msg})
             return
-        ret = self._push_right(json_length + json_message)
+        ret = self._push_right(json_message)
         if not ret:
             msg = "Transfer interrupted"
             request.complete({"__error": msg})

cms/async/Utils.py

@@ -25,7 +25,6 @@
 
 import sys
 import datetime
-import struct
 import time
 
 import simplejson as json
@@ -40,35 +39,6 @@ def random_string(length):
     return "".join(choice(letters) for unused_i in xrange(length))
 
 
-def encode_length(length):
-    """Encode an integer as a 4 bytes string
-
-    length (int): the integer to encode
-    return (string): a 4 bytes representation of length
-
-    """
-    try:
-        return struct.pack(">I", length)
-    except Exception as error:
-        print >> sys.stderr, "Can't encode length: %s %r" % (length, error)
-        raise ValueError
-
-
-def decode_length(string):
-    """Decode an integer from a 4 bytes string
-
-    string (string): a 4 bytes representation of an integer
-    return (int): the corresponding integer
-
-    """
-    try:
-        val, = struct.unpack(">I", string[:4])
-        return val
-    except:
-        print >> sys.stderr, "Can't decode length"
-        raise ValueError
-
-
 def encode_json(obj):
     """Encode a dictionary as a JSON string; on failure, returns None.