Fix seek and tell in BlockingQueue

Currently seek() throws IOError conditionally and tell() returns the
maximum transfer size. This patch fixes these problems.

Change-Id: Ie8bf359457de975a8ae6373a73b5a835e53f2410

2 files changed, 15 insertions, 14 deletions

diff --git a/oslo/vmware/image_transfer.py b/oslo/vmware/image_transfer.py
index a86773d..d05ad6c 100644
--- a/oslo/vmware/image_transfer.py
+++ b/oslo/vmware/image_transfer.py
@@ -79,22 +79,17 @@ class BlockingQueue(queue.LightQueue):
 
     # Below methods are provided in order to enable treating the queue
     # as a file handle.
-    # Note(vui): When file transfer size is not specified, we raise IOError to
-    # prevent incorrect predetermination of file length by readers.
 
     def seek(self, offset, whence=0):
-        if self._max_transfer_size is 0:
-            raise IOError(errno.ESPIPE, "Illegal seek")
+        """Set the file's current position at the offset.
 
-    def tell(self):
-        """Get size of the file to be read.
-
-        We interpret _max_transfer_size=0 as stream mode and raise IOError
-        to prevent incorrect predetermination of file length by readers.
+        This method throws IOError since seek cannot be supported for a pipe.
         """
-        if self._max_transfer_size is 0:
-            raise IOError(errno.ESPIPE, "Illegal seek")
-        return self._max_transfer_size
+        raise IOError(errno.ESPIPE, "Illegal seek")
+
+    def tell(self):
+        """Get the current file position."""
+        return self._transferred
 
     def close(self):
         pass
diff --git a/tests/test_image_transfer.py b/tests/test_image_transfer.py
index 1965cd9..6d81513 100644
--- a/tests/test_image_transfer.py
+++ b/tests/test_image_transfer.py
@@ -61,10 +61,16 @@ class BlockingQueueTest(base.TestCase):
         exp_calls = [mock.call([1])] * write_count
         self.assertEqual(exp_calls, queue.put.call_args_list)
 
+    def test_seek(self):
+        queue = image_transfer.BlockingQueue(10, 30)
+        self.assertRaises(IOError, queue.seek, 5)
+
     def test_tell(self):
-        max_transfer_size = 30
         queue = image_transfer.BlockingQueue(10, 30)
-        self.assertEqual(max_transfer_size, queue.tell())
+        self.assertEqual(0, queue.tell())
+        queue.get = mock.Mock(return_value=[1] * 10)
+        queue.read(10)
+        self.assertEqual(10, queue.tell())
 
 
 class ImageWriterTest(base.TestCase):