Added efficient HEAD request handling

This is not implemented using a `def head()` in the view, as the HEAD request
should return all headers that the GET request would send. Hence,
updated the server logic to provide a proper HEAD request.

private_storage/servers.py

@@ -78,6 +78,10 @@ class DjangoStreamingServer(object):
         # As of Django 1.8, FileResponse triggers 'wsgi.file_wrapper' in Django's WSGIHandler.
         # This uses efficient file streaming, such as sendfile() in uWSGI.
         # When the WSGI container doesn't provide 'wsgi.file_wrapper', it submits the file in 4KB chunks.
+        if private_file.request.method == 'HEAD':
+            # Avoid reading the file at all
+            response = HttpResponse()
+        else:
             response = FileResponse(private_file.open())
         response['Content-Type'] = private_file.content_type
         response['Content-Length'] = size
@@ -113,7 +117,15 @@ class DjangoServer(DjangoStreamingServer):
             return DjangoStreamingServer.serve(private_file)
         else:
             # Using Django's serve gives If-Modified-Since support out of the box.
-            return serve(private_file.request, full_path, document_root='/', show_indexes=False)
+            response = serve(private_file.request, full_path, document_root='/', show_indexes=False)
+            if private_file.request.method == 'HEAD':
+                # Avoid reading the file at all, copy FileResponse headers
+                head_response = HttpResponse(status=response.status_code)
+                for header, value in response.items():
+                    head_response[header] = value
+                return head_response
+            else:
+                return response
 
 
 class ApacheXSendfileServer(object):

private_storage/tests/test_views.py

 # encoding: utf-8
 from django.contrib.auth.models import User
 from django.core.files.uploadedfile import SimpleUploadedFile
+from django.http import FileResponse
 from django.test import RequestFactory
 
 from private_storage.tests.models import CustomerDossier
@@ -19,8 +20,12 @@ class ViewTests(PrivateFileTestCase):
             file=SimpleUploadedFile('test4.txt', b'test4')
         )
 
-        request = RequestFactory().get('/cust1/file/')
-        request.user = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
+        superuser = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
+
+        # Test HEAD calls too
+        for method in ('GET', 'HEAD'):
+            request = RequestFactory().generic(method, '/cust1/file/')
+            request.user = superuser
 
             # Initialize locally, no need for urls.py etc..
             # This behaves like a standard DetailView
@@ -35,6 +40,10 @@ class ViewTests(PrivateFileTestCase):
                 request,
                 customer='cust1',
             )
+            if method == 'HEAD':
+                self.assertNotIsInstance(response, FileResponse)
+                self.assertEqual(response.content, b'')
+            else:
                 self.assertEqual(list(response.streaming_content), [b'test4'])
             self.assertEqual(response['Content-Type'], 'text/plain')
             self.assertEqual(response['Content-Length'], '5')
@@ -50,20 +59,27 @@ class ViewTests(PrivateFileTestCase):
         )
         self.assertExists('CustomerDossier', 'cust2', 'test5.txt')
 
-        request = RequestFactory().get('/cust1/file/')
-        request.user = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
-        request.META['HTTP_USER_AGENT'] = 'Test'
-
         # Initialize locally, no need for urls.py etc..
         # This behaves like a standard DetailView
         view = PrivateStorageView.as_view(
             content_disposition='attachment',
         )
+        superuser = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
+
+        # Test HEAD calls too
+        for method in ('GET', 'HEAD'):
+            request = RequestFactory().generic(method, '/cust1/file/')
+            request.user = superuser
+            request.META['HTTP_USER_AGENT'] = 'Test'
 
             response = view(
                 request,
                 path='CustomerDossier/cust2/test5.txt'
             )
+            if method == 'HEAD':
+                self.assertNotIsInstance(response, FileResponse)
+                self.assertEqual(response.content, b'')
+            else:
                 self.assertEqual(list(response.streaming_content), [b'test5'])
             self.assertEqual(response['Content-Type'], 'text/plain')
             self.assertEqual(response['Content-Length'], '5')
@@ -85,7 +101,7 @@ class ViewTests(PrivateFileTestCase):
         view = PrivateStorageView.as_view(
             content_disposition='attachment',
         )
-        admin = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
+        superuser = User.objects.create_superuser('admin', 'admin@example.com', 'admin')
 
         for user_agent, expect_header in [
                 ('Firefox', "attachment; filename*=UTF-8''Heiz%C3%B6lr%C3%BCcksto%C3%9Fabd%C3%A4mpfung.txt"),
@@ -93,14 +109,19 @@ class ViewTests(PrivateFileTestCase):
                 ('MSIE', 'attachment; filename=Heiz%C3%B6lr%C3%BCcksto%C3%9Fabd%C3%A4mpfung.txt'),
                 ]:
 
-            request = RequestFactory().get('/cust1/file/')
-            request.user = admin
+            for method in ('GET', 'HEAD'):
+                request = RequestFactory().generic(method, '/cust1/file/')
+                request.user = superuser
                 request.META['HTTP_USER_AGENT'] = user_agent
 
                 response = view(
                     request,
                     path=u'CustomerDossier/cust2/Heizölrückstoßabdämpfung.txt'
                 )
+                if method == 'HEAD':
+                    self.assertNotIsInstance(response, FileResponse)
+                    self.assertEqual(response.content, b'')
+                else:
                     self.assertEqual(list(response.streaming_content), [b'test5'])
                 self.assertEqual(response['Content-Type'], 'text/plain')
                 self.assertEqual(response['Content-Length'], '5')

private_storage/views.py

@@ -3,7 +3,7 @@ Views to send private files.
 """
 import os
 
-from django.http import Http404, HttpResponseForbidden
+from django.http import Http404, HttpResponse, HttpResponseForbidden
 from django.utils.module_loading import import_string
 from django.views.generic import View
 from django.views.generic.detail import SingleObjectMixin