addressing comments

Signed-off-by: grantlouisherman <grantlouisherman041@gmail.com>

Author: grantlouisherman

Lib/asyncio/unix_events.py

@@ -449,7 +449,7 @@ def _sock_sendfile_native_impl(self, fut, registered_fd, sock, fileno,
                                 offset, count, blocksize, total_sent)
 
     def _sock_sendfile_update_filepos(self, fileno, offset, total_sent):
-        if total_sent > 0:
+        if total_sent >= 0:
             os.lseek(fileno, offset, os.SEEK_SET)
 
     def _sock_add_cancellation_callback(self, fut, sock):

Lib/test/test_asyncio/test_sendfile.py

@@ -242,10 +242,14 @@ async def _sock_sendfile_fail(sock, file, offset, count):
                     ret = self.run_loop(self.loop.sock_sendfile(sock, f, offset, None))
             else:
                 ret = self.run_loop(self.loop.sock_sendfile(sock, f, offset, None))
+
             self.assertEqual(f.tell(), len(data))
-            sock.close()
-            self.run_loop(proto.wait_closed())
-            self.assertEqual(ret, len(data) - offset)
+
+        sock.close()
+        self.run_loop(proto.wait_closed())
+
+        self.assertEqual(ret, len(data) - offset)
+
 
     def test_sock_sendfile_offset(self):
         data = b'abcdef'
@@ -254,6 +258,25 @@ def test_sock_sendfile_offset(self):
                 with self.subTest(offset=offset, force_fallback=force_fallback):
                     self.check_sock_sendfile_offset(data, offset, force_fallback)
 
+
+    def check_sendfile_offset(self, offset, fallback):
+        srv_proto, cli_proto = self.prepare_sendfile()
+        self.file.seek(123)
+        coro = self.loop.sendfile(cli_proto.transport, self.file, offset, fallback=fallback)
+        ret = self.run_loop(coro)
+        cli_proto.transport.close()
+        self.run_loop(srv_proto.done)
+        self.assertEqual(ret, len(self.DATA) - offset)
+        self.assertEqual(srv_proto.nbytes, len(self.DATA) - offset)
+        self.assertEqual(srv_proto.data, self.DATA[offset:])
+        self.assertEqual(self.file.tell(), len(self.DATA))
+
+    def test_sendfile_offset(self):
+        for offset in (0, len(self.DATA) // 2, len(self.DATA)):
+            for fallback in (False, True):
+                with self.subTest(offset=offset, fallback=fallback):
+                    self.check_sendfile_offset(offset, fallback)
+
     def test_sock_sendfile_mix_with_regular_send(self):
         buf = b"mix_regular_send" * (4 * 1024)  # 64 KiB
         sock, proto = self.prepare_socksendfile()