From 3e69ed171dd5a623ffa7f45dc3fb3373199db47a Mon Sep 17 00:00:00 2001
From: Omer Katz <omer.drow@gmail.com>
Date: Thu, 2 Oct 2014 17:18:32 +0300
Subject: [PATCH] Added an optional LRU cache to the JSON encoder.

---
 rest_framework/compat.py         | 13 +++++++++
 rest_framework/settings.py       |  3 +-
 rest_framework/utils/encoders.py | 49 +++++++++++++++++++-------------
 3 files changed, 44 insertions(+), 21 deletions(-)

diff --git a/rest_framework/compat.py b/rest_framework/compat.py
index 3993cee6d..8de0496c6 100644
--- a/rest_framework/compat.py
+++ b/rest_framework/compat.py
@@ -310,3 +310,16 @@ except ImportError:
         klass.__unicode__ = klass.__str__
         klass.__str__ = lambda self: self.__unicode__().encode('utf-8')
         return klass
+
+try:
+    from functools import lru_cache
+except ImportError:
+    try:
+        from backports.functools_lru_cache import lru_cache
+    except ImportError:
+        def lru_cache(maxsize=100, typed=False):  # When the LRU cache decorator is not available replace with a stub.
+            def decorating_function(f):
+                def wrapper(*args, **kwargs):
+                    return f(*args, **kwargs)
+                return wrapper
+            return decorating_function
diff --git a/rest_framework/settings.py b/rest_framework/settings.py
index 1e8c27fc3..6085b8a46 100644
--- a/rest_framework/settings.py
+++ b/rest_framework/settings.py
@@ -111,7 +111,8 @@ DEFAULTS = {
     'UNICODE_JSON': True,
     'COMPACT_JSON': True,
     'COERCE_DECIMAL_TO_STRING': True,
-    'UPLOADED_FILES_USE_URL': True
+    'UPLOADED_FILES_USE_URL': True,
+    'ENCODER_LRU_CACHE_SIZE': 1024
 }
 
 
diff --git a/rest_framework/utils/encoders.py b/rest_framework/utils/encoders.py
index 486186c94..e02014ed8 100644
--- a/rest_framework/utils/encoders.py
+++ b/rest_framework/utils/encoders.py
@@ -2,16 +2,19 @@
 Helper classes for parsers.
 """
 from __future__ import unicode_literals
-from django.db.models.query import QuerySet
-from django.utils import six, timezone
-from django.utils.datastructures import SortedDict
-from django.utils.functional import Promise
-from rest_framework.compat import force_text
 import datetime
 import decimal
 import types
 import json
 
+from django.db.models.query import QuerySet
+from django.utils import six, timezone
+from django.utils.datastructures import SortedDict
+from django.utils.functional import Promise
+
+from rest_framework.compat import force_text, lru_cache
+from rest_framework.settings import api_settings
+
 
 class JSONEncoder(json.JSONEncoder):
     """
@@ -19,11 +22,28 @@ class JSONEncoder(json.JSONEncoder):
     decimal types, generators and other basic python objects.
     """
     def default(self, obj):
-        # For Date Time string spec, see ECMA 262
-        # http://ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
         if isinstance(obj, Promise):
             return force_text(obj)
-        elif isinstance(obj, datetime.datetime):
+        elif isinstance(obj, QuerySet):
+            return tuple(obj)
+        elif hasattr(obj, '__getitem__'):
+            try:
+                return dict(obj)
+            except:
+                pass
+        elif hasattr(obj, 'tolist'):
+            # Numpy arrays and array scalars.
+            return obj.tolist()
+        elif hasattr(obj, '__iter__'):
+            return tuple(item for item in obj)
+
+        return self._default(obj)
+
+    @lru_cache(typed=True, maxsize=api_settings.ENCODER_LRU_CACHE_SIZE)
+    def _default(self, obj):
+        # For Date Time string spec, see ECMA 262
+        # http://ecma-international.org/ecma-262/5.1/#sec-15.9.1.15
+        if isinstance(obj, datetime.datetime):
             representation = obj.isoformat()
             if obj.microsecond:
                 representation = representation[:23] + representation[26:]
@@ -44,18 +64,7 @@ class JSONEncoder(json.JSONEncoder):
         elif isinstance(obj, decimal.Decimal):
             # Serializers will coerce decimals to strings by default.
             return float(obj)
-        elif isinstance(obj, QuerySet):
-            return tuple(obj)
-        elif hasattr(obj, 'tolist'):
-            # Numpy arrays and array scalars.
-            return obj.tolist()
-        elif hasattr(obj, '__getitem__'):
-            try:
-                return dict(obj)
-            except:
-                pass
-        elif hasattr(obj, '__iter__'):
-            return tuple(item for item in obj)
+
         return super(JSONEncoder, self).default(obj)