Use a mmap file to read data in StaticRoute

aiohttp/web_urldispatcher.py

@@ -6,6 +6,7 @@
 import re
 import os
 import inspect
+import mmap
 
 from urllib.parse import urlencode, unquote
 
@@ -235,19 +236,18 @@ def _sendfile_fallback(self, req, resp, fobj, count):
         transferred in chunks controlled by the `chunk_size` argument to
         :class:`StaticRoute`.
         """
+        f_mm = mmap.mmap(fobj.fileno(), count, access=mmap.ACCESS_READ)
         chunk_size = self._chunk_size
 
-        chunk = fobj.read(chunk_size)
-        while chunk and count > chunk_size:
-            resp.write(chunk)
-            yield from resp.drain()
-            count = count - chunk_size
-            chunk = fobj.read(chunk_size)
+        chunk_starts = range(0, count, chunk_size)
+        chunk_stops = range(chunk_size, count+chunk_size, chunk_size)
 
-        if chunk:
-            resp.write(chunk[:count])
+        for i, j in zip(chunk_starts, chunk_stops):
+            resp.write(f_mm[i:j])
             yield from resp.drain()
 
+        f_mm.close()
+
     if hasattr(os, "sendfile"):  # pragma: no cover
         _sendfile = _sendfile_system
     else:  # pragma: no cover
@@ -281,6 +281,10 @@ def handle(self, request):
         file_size = st.st_size
 
         resp.content_length = file_size
+
+        if file_size == 0:
+            return resp
+
         yield from resp.prepare(request)
 
         with open(filepath, 'rb') as f:

tests/test_web_functional.py

@@ -1018,6 +1018,26 @@ def go(dirname, filename):
 
         self.loop.run_until_complete(go(here, filename))
 
+    def test_static_file_empty(self):
+
+        @asyncio.coroutine
+        def go(dirname, filename):
+            app, _, url = yield from self.create_server(
+                'GET', '/static/' + filename
+            )
+            app.router.add_static('/static', dirname)
+
+            resp = yield from request('GET', url, loop=self.loop)
+            self.assertEqual(200, resp.status)
+            txt = yield from resp.text()
+            self.assertEqual('', txt)
+            self.assertEqual('0', resp.headers['CONTENT-LENGTH'])
+            resp.close()
+
+        here = os.path.dirname(__file__)
+        filename = 'empty.dat'
+        self.loop.run_until_complete(go(here, filename))
+
 
 class TestStaticFileSendfileFallback(StaticFileMixin,
                                      unittest.TestCase):