avocado.utils.datadrainer: introduce buffered file descriptor drainer

Signed-off-by: NCleber Rosa <crosa@redhat.com>

avocado/utils/datadrainer.py

@@ -143,3 +143,25 @@ class FDDrainer(BaseDrainer):
     def write(self, data):
         # necessary to avoid pylint W0223
         raise NotImplementedError
+
+
+class BufferFDDrainer(FDDrainer):
+    """
+    Drains data from a file descriptor and stores it in an internal buffer
+    """
+
+    name = 'avocado.utils.datadrainer.BufferFDDrainer'
+
+    def __init__(self, source, stop_check=None, name=None):
+        super(BufferFDDrainer, self).__init__(source, stop_check, name)
+        self._data = io.BytesIO()
+
+    def write(self, data):
+        self._data.write(data)
+
+    @property
+    def data(self):
+        """
+        Returns the buffer data, as bytes
+        """
+        return self._data.getvalue()

selftests/unit/test_utils_datadrainer.py

@@ -71,3 +71,31 @@ class CustomSocket(unittest.TestCase):
     def tearDown(self):
         self.socket1.close()
         self.socket2.close()
+
+
+class SocketBuffer(datadrainer.BufferFDDrainer):
+
+    name = 'test_utils_datadrainer.SocketBuffer'
+
+    def __init__(self, source):
+        super(SocketBuffer, self).__init__(source)
+        self._stop_check = lambda: len(self.data) > 2
+
+
+class CustomSocketBuffer(unittest.TestCase):
+
+    def setUp(self):
+        self.socket1, self.socket2 = socket.socketpair(socket.AF_UNIX)
+
+    def test(self):
+        socket_drainer = SocketBuffer(self.socket2.fileno())
+        socket_drainer.start()
+        self.socket1.send(b'1')
+        self.socket1.send(b'2')
+        self.socket1.send(b'3')
+        socket_drainer.wait()
+        self.assertEqual(socket_drainer.data, b'123')
+
+    def tearDown(self):
+        self.socket1.close()
+        self.socket2.close()