BF+TEST - fix trackvis swapped endian read error with test

Author: matthew-brett

nibabel/tests/test_trackvis.py

@@ -5,6 +5,7 @@
 import numpy as np
 
 from .. import trackvis as tv
+from ..volumeutils import swapped_code
 
 from nose.tools import assert_true, assert_false, assert_equal, assert_raises
 
@@ -46,10 +47,10 @@ def streams_equal(stream1, stream2):
         return False
     if stream1[1] is None:
         if not stream2[1] is None:
-            return false
+            return False
     if stream1[2] is None:
         if not stream2[2] is None:
-            return false
+            return False
     if not np.all(stream1[1] == stream1[1]):
         return False
     if not np.all(stream1[2] == stream1[2]):
@@ -75,6 +76,12 @@ def test_round_trip():
     out_f.seek(0)
     streams2, hdr = tv.read(out_f)
     assert_true(streamlist_equal(streams, streams2))
+    # test that we can write in different endianness and get back same result
+    out_f.seek(0)
+    tv.write(out_f, streams, {}, swapped_code)
+    out_f.seek(0)
+    streams2, hdr = tv.read(out_f)
+    assert_true(streamlist_equal(streams, streams2))
     # test that we can get out and pass in generators
     out_f.seek(0)
     streams3, hdr = tv.read(out_f, as_generator=True)

nibabel/trackvis.py

@@ -125,13 +125,6 @@ def read(fileobj, as_generator=False):
     if str(hdr['id_string'])[:5] != 'TRACK':
         raise HeaderError('Expecting TRACK as first '
                           '5 characters of id_string')
-    version = hdr['version']
-    if version not in (1, 2):
-        raise HeaderError('Reader only supports versions 1 and 2')
-    if version == 1:
-        hdr = np.ndarray(shape=(),
-                         dtype=header_1_dtype,
-                         buffer=hdr_str)
     if hdr['hdr_size'] == 1000:
         endianness = native_code
     else:
@@ -140,6 +133,16 @@ def read(fileobj, as_generator=False):
             raise HeaderError('Invalid hdr_size of %s'
                               % hdr['hdr_size'])
         endianness = swapped_code
+    # Check version and adapt structure accordingly
+    version = hdr['version']
+    if version not in (1, 2):
+        raise HeaderError('Reader only supports versions 1 and 2')
+    if version == 1: # make a new header with the same data
+        hdr = np.ndarray(shape=(),
+                         dtype=header_1_dtype,
+                         buffer=hdr_str)
+        if endianness == swapped_code:
+            hdr = hdr.newbyteorder()
     n_s = hdr['n_scalars']
     n_p = hdr['n_properties']
     f4dt = np.dtype(endianness + 'f4')