BF: disable float128 datadtype if no binary128

We should not be using float128 data format in nifti if we don't have
binary128 format on this machine.

Closes gh-131.

Author: matthew-brett

nibabel/nifti1.py

@@ -20,6 +20,7 @@
 from .quaternions import fillpositive, quat2mat, mat2quat
 from . import analyze # module import
 from .spm99analyze import SpmAnalyzeHeader
+from .casting import have_binary128
 
 # Needed for quaternion calculation
 FLOAT32_EPS_3 = -np.finfo(np.float32).eps * 3
@@ -76,13 +77,12 @@
 header_dtype = np.dtype(header_dtd)
 
 # datatypes not in analyze format, with codes
-try:
-    _float128t = np.float128
-except AttributeError:
+if have_binary128():
+    # Only enable 128 bit floats if we really have IEEE binary 128 longdoubles
+    _float128t = np.longdouble
+    _complex256t = np.longcomplex
+else:
     _float128t = np.void
-try:
-    _complex256t = np.complex256
-except AttributeError:
     _complex256t = np.void
 
 _dtdefs = ( # code, label, dtype definition, niistring

nibabel/tests/test_nifti1.py

@@ -14,7 +14,7 @@
 
 import numpy as np
 
-from ..casting import type_info
+from ..casting import type_info, have_binary128
 from ..tmpdirs import InTemporaryDirectory
 from ..spatialimages import HeaderDataError
 from ..affines import from_matvec
@@ -309,6 +309,14 @@ def test_binblock_is_file(self):
         hdr.write_to(str_io)
         assert_equal(str_io.getvalue(), hdr.binaryblock + ZEROB * 4)
 
+    def test_float128(self):
+        hdr = self.header_class()
+        if have_binary128():
+            hdr.set_data_dtype(np.longdouble)
+            assert_equal(hdr.get_data_dtype().type, np.longdouble)
+        else:
+            assert_raises(HeaderDataError, hdr.set_data_dtype, np.longdouble)
+
 
 class TestNifti1Image(tana.TestAnalyzeImage):
     # Run analyze-flavor spatialimage tests