Faster JSON encoder/decoder

Improve performance of FreeIPA's JSON serializer and deserializer.

* Don't indent and sort keys. Both options trigger a slow path in
  Python's json package. Without indention and sorting, encoding
  mostly happens in optimized C code.
* Replace O(n) type checks with O(1) type lookup and eliminate
  the use of isinstance().
* Check each client capability only once for every conversion.
* Use decoder's obj_hook feature to traverse the object tree once and
  to eliminate calls to isinstance().

Closes: https://fedorahosted.org/freeipa/ticket/6655
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaserver/rpcserver.py

@@ -25,8 +25,8 @@ Also see the `ipalib.rpc` module.
 
 from xml.sax.saxutils import escape
 import os
-import json
 import traceback
+
 import gssapi
 import requests
 
@@ -483,13 +483,12 @@ class jsonserver(WSGIExecutioner, HTTP_Status):
             principal=unicode(principal),
             version=unicode(VERSION),
         )
-        response = json_encode_binary(response, version)
-        dump = json.dumps(response, sort_keys=True, indent=4)
+        dump = json_encode_binary(response, version)
         return dump.encode('utf-8')
 
     def unmarshal(self, data):
         try:
-            d = json.loads(data)
+            d = json_decode_binary(data)
         except ValueError as e:
             raise JSONError(error=e)
         if not isinstance(d, dict):
@@ -498,7 +497,6 @@ class jsonserver(WSGIExecutioner, HTTP_Status):
             raise JSONError(error=_('Request is missing "method"'))
         if 'params' not in d:
             raise JSONError(error=_('Request is missing "params"'))
-        d = json_decode_binary(d)
         method = d['method']
         params = d['params']
         _id = d.get('id')