Improve DownloadView for cStringIO file download response

django_downloadview/response.py

@@ -14,7 +14,7 @@ class DownloadResponse(HttpResponse):
 
     """
     def __init__(self, file_instance, attachment=True, basename=None,
-                 status=200, content_type=None):
+                 status=200, content_type=None, size=None):
         """Constructor.
 
         It differs a bit from HttpResponse constructor.
@@ -42,6 +42,9 @@ class DownloadResponse(HttpResponse):
           response (default implementation uses mimetypes, based on file name).
           Defaults is ``None``.
 
+        size:
+          Size of the file response
+
         """
         self.file = file_instance
         super(DownloadResponse, self).__init__(content=self.file,
@@ -49,6 +52,8 @@ class DownloadResponse(HttpResponse):
                                                content_type=content_type)
         self.basename = basename
         self.attachment = attachment
+        self.content_type = content_type
+        self.size = size
         if not content_type:
             del self['Content-Type']  # Will be set later.
         # Apply default headers.
@@ -69,7 +74,7 @@ class DownloadResponse(HttpResponse):
         except AttributeError:
             headers = {}
             headers['Content-Type'] = self.get_content_type()
-            headers['Content-Length'] = self.file.size
+            headers['Content-Length'] = self.get_size()
             if self.attachment:
                 headers['Content-Disposition'] = 'attachment; filename=%s' \
                                                  % self.get_basename()
@@ -95,12 +100,15 @@ class DownloadResponse(HttpResponse):
 
     def get_content_type(self):
         """Return a suitable "Content-Type" header for ``self.file``."""
-        try:
-            return self.file.content_type
-        except AttributeError:
-            content_type_template = '%(mime_type)s; charset=%(charset)s'
-            return content_type_template % {'mime_type': self.get_mime_type(),
-                                            'charset': self.get_charset()}
+        if not self.content_type:
+            try:
+                return self.file.content_type
+            except AttributeError:
+                content_type_template = '%(mime_type)s; charset=%(charset)s'
+                return content_type_template % {
+                    'mime_type': self.get_mime_type(),
+                    'charset': self.get_charset()}
+        return self.content_type
 
     def get_mime_type(self):
         """Return mime-type of the file."""
@@ -119,6 +127,12 @@ class DownloadResponse(HttpResponse):
         """Return the charset of the file to serve."""
         return settings.DEFAULT_CHARSET
 
+    def get_size(self):
+        """Return the size of the file to serve."""
+        if not self.size:
+            self.size = self.file.size
+        return self.size
+
 
 def is_download_response(response):
     """Return ``True`` if ``response`` is a download response.

django_downloadview/views.py

@@ -40,6 +40,15 @@ class DownloadMixin(object):
     def get_basename(self):
         return self.basename
 
+    def get_size(self):
+        return self.get_file().size
+
+    def get_modification_time(self):
+        return self.get_file().modified_time
+
+    def get_content_type(self):
+        return self.get_file().content_type
+
     def render_to_response(self, *args, **kwargs):
         """Returns a response with a file as attachment."""
         # Respect the If-Modified-Since header.
@@ -47,16 +56,18 @@ class DownloadMixin(object):
         if_modified_since = self.request.META.get('HTTP_IF_MODIFIED_SINCE',
                                                   None)
         if if_modified_since is not None:
-            modification_time = file_instance.modified_time
-            size = file_instance.size
+            modification_time = self.get_modification_time()
+            size = self.get_size()
             if not was_modified_since(if_modified_since, modification_time,
                                       size):
-                content_type = file_instance.content_type
+                content_type = self.get_content_type()
                 return HttpResponseNotModified(content_type=content_type)
         # Return download response.
         response_kwargs = {'file_instance': file_instance,
                            'attachment': self.attachment,
-                           'basename': self.get_basename()}
+                           'basename': self.get_basename(),
+                           'size': self.get_size(),
+                           'content_type': self.get_content_type()}
         response_kwargs.update(kwargs)
         response = self.response_class(**response_kwargs)
         return response