Merge pull request #109 from Galvant/binblockread_retries

Binblockread retries

instruments/__init__.py

@@ -36,7 +36,7 @@
 # In keeping with PEP-396, we define a version number of the form
 # {major}.{minor}[.{postrelease}]{prerelease-tag}
 
-__version__ = "0.0.1"
+__version__ = "0.0.2"
 
 __title__ = "instrumentkit"
 __description__ = "Test and measurement communication library"

instruments/abstract_instruments/instrument.py

@@ -282,7 +282,20 @@ def binblockread(self, data_width, fmt=None):
 
             # Read in the data bytes, and pass them to numpy using the specified
             # data type (format).
-            return np.frombuffer(self._file.read_raw(num_of_bytes), dtype=fmt)
+            # This is looped in case a communication timeout occurs midway
+            # through transfer and multiple reads are required
+            tries = 3
+            data = self._file.read_raw(num_of_bytes)
+            while len(data) < num_of_bytes:
+                old_len = len(data)
+                data += self._file.read_raw(num_of_bytes - old_len)
+                if old_len == len(data):
+                    tries -= 1
+                if tries == 0:
+                    raise IOError("Did not read in the required number of bytes"
+                                  "during binblock read. Got {}, expected "
+                                  "{}".format(len(data), num_of_bytes))
+            return np.frombuffer(data, dtype=fmt)
 
     # CLASS METHODS #
 

instruments/tests/test_base_instrument.py

@@ -10,9 +10,8 @@
 
 from builtins import bytes
 
-# pylint: disable=unused-import
 from nose.tools import raises
-import quantities as pq
+import mock
 
 import numpy as np
 
@@ -21,6 +20,8 @@
 
 # TESTS ######################################################################
 
+# pylint: disable=no-member,protected-access
+
 
 def test_instrument_binblockread():
     with expected_protocol(
@@ -32,3 +33,36 @@ def test_instrument_binblockread():
         sep="\n"
     ) as inst:
         np.testing.assert_array_equal(inst.binblockread(2), [0, 1, 2, 3, 4])
+
+
+def test_instrument_binblockread_two_reads():
+    inst = ik.Instrument.open_test()
+    data = bytes.fromhex("00000001000200030004")
+    inst._file.read_raw = mock.MagicMock(
+        side_effect=[b"#", b"2", b"10", data[:6], data[6:]]
+    )
+
+    np.testing.assert_array_equal(inst.binblockread(2), [0, 1, 2, 3, 4])
+
+    calls_expected = [1, 1, 2, 10, 4]
+    calls_actual = [call[0][0] for call in inst._file.read_raw.call_args_list]
+    np.testing.assert_array_equal(calls_expected, calls_actual)
+
+
+@raises(IOError)
+def test_instrument_binblockread_too_many_reads():
+    inst = ik.Instrument.open_test()
+    data = bytes.fromhex("00000001000200030004")
+    inst._file.read_raw = mock.MagicMock(
+        side_effect=[b"#", b"2", b"10", data[:6], b"", b"", b""]
+    )
+
+    _ = inst.binblockread(2)
+
+
+@raises(IOError)
+def test_instrument_binblockread_bad_block_start():
+    inst = ik.Instrument.open_test()
+    inst._file.read_raw = mock.MagicMock(return_value=b"@")
+
+    _ = inst.binblockread(2)