--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/middleware/cache.py	Fri Jul 18 18:22:23 2008 +0000
@@ -0,0 +1,97 @@
+from django.conf import settings
+from django.core.cache import cache
+from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age
+
+class CacheMiddleware(object):
+    """
+    Cache middleware. If this is enabled, each Django-powered page will be
+    cached (based on URLs).
+
+    Only parameter-less GET or HEAD-requests with status code 200 are cached.
+
+    The number of seconds each page is stored for is set by the
+    "max-age" section of the response's "Cache-Control" header, falling back to
+    the CACHE_MIDDLEWARE_SECONDS setting if the section was not found.
+
+    If CACHE_MIDDLEWARE_ANONYMOUS_ONLY is set to True, only anonymous requests
+    (i.e., those not made by a logged-in user) will be cached. This is a
+    simple and effective way of avoiding the caching of the Django admin (and
+    any other user-specific content).
+
+    This middleware expects that a HEAD request is answered with a response
+    exactly like the corresponding GET request.
+
+    When a hit occurs, a shallow copy of the original response object is
+    returned from process_request.
+
+    Pages will be cached based on the contents of the request headers
+    listed in the response's "Vary" header. This means that pages shouldn't
+    change their "Vary" header.
+
+    This middleware also sets ETag, Last-Modified, Expires and Cache-Control
+    headers on the response object.
+    """
+    def __init__(self, cache_timeout=None, key_prefix=None, cache_anonymous_only=None):
+        self.cache_timeout = cache_timeout
+        if cache_timeout is None:
+            self.cache_timeout = settings.CACHE_MIDDLEWARE_SECONDS
+        self.key_prefix = key_prefix
+        if key_prefix is None:
+            self.key_prefix = settings.CACHE_MIDDLEWARE_KEY_PREFIX
+        if cache_anonymous_only is None:
+            self.cache_anonymous_only = getattr(settings, 'CACHE_MIDDLEWARE_ANONYMOUS_ONLY', False)
+        else:
+            self.cache_anonymous_only = cache_anonymous_only
+
+    def process_request(self, request):
+        "Checks whether the page is already cached and returns the cached version if available."
+        if self.cache_anonymous_only:
+            assert hasattr(request, 'user'), "The Django cache middleware with CACHE_MIDDLEWARE_ANONYMOUS_ONLY=True requires authentication middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.auth.middleware.AuthenticationMiddleware' before the CacheMiddleware."
+
+        if not request.method in ('GET', 'HEAD') or request.GET:
+            request._cache_update_cache = False
+            return None # Don't bother checking the cache.
+
+        if self.cache_anonymous_only and request.user.is_authenticated():
+            request._cache_update_cache = False
+            return None # Don't cache requests from authenticated users.
+
+        cache_key = get_cache_key(request, self.key_prefix)
+        if cache_key is None:
+            request._cache_update_cache = True
+            return None # No cache information available, need to rebuild.
+
+        response = cache.get(cache_key, None)
+        if response is None:
+            request._cache_update_cache = True
+            return None # No cache information available, need to rebuild.
+
+        request._cache_update_cache = False
+        return response
+
+    def process_response(self, request, response):
+        "Sets the cache, if needed."
+        if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache:
+            # We don't need to update the cache, just return.
+            return response
+        if request.method != 'GET':
+            # This is a stronger requirement than above. It is needed
+            # because of interactions between this middleware and the
+            # HTTPMiddleware, which throws the body of a HEAD-request
+            # away before this middleware gets a chance to cache it.
+            return response
+        if not response.status_code == 200:
+            return response
+        # Try to get the timeout from the "max-age" section of the "Cache-
+        # Control" header before reverting to using the default cache_timeout
+        # length.
+        timeout = get_max_age(response)
+        if timeout == None:
+            timeout = self.cache_timeout
+        elif timeout == 0:
+            # max-age was set to 0, don't bother caching.
+            return response
+        patch_response_headers(response, timeout)
+        cache_key = learn_cache_key(request, response, timeout, self.key_prefix)
+        cache.set(cache_key, response, timeout)
+        return response