BF - add missing files for byteswapping

dipy/utils/arrfuncs.py

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+""" Utilities to manipulate numpy arrays """
+
+import sys
+
+import numpy as np
+
+from nibabel.volumeutils import endian_codes, native_code, swapped_code
+
+
+def as_native_array(arr):
+    """ Return `arr` as native byteordered array
+
+    If arr is already native byte ordered, return unchanged.  If it is opposite
+    endian, then make a native byte ordered copy and return that
+
+    Parameters
+    ----------
+    arr : ndarray
+
+    Returns
+    -------
+    native_arr : ndarray
+        If `arr` was native order, this is just `arr`. Otherwise it's a new
+        array such that ``np.all(native_arr == arr)``, with native byte
+        ordering.
+    """
+    if endian_codes[arr.dtype.byteorder] == native_code:
+        return arr
+    return arr.byteswap().newbyteorder()
+

dipy/utils/tests/test_arrfuncs.py

@@ -0,0 +1,30 @@
+""" Testing array utilities
+"""
+
+import sys
+
+import numpy as np
+
+from ..arrfuncs import as_native_array
+
+from numpy.testing import (assert_array_almost_equal,
+                           assert_array_equal)
+
+from nose.tools import assert_true, assert_false, assert_equal, assert_raises
+
+NATIVE_ORDER = '<' if sys.byteorder == 'little' else '>'
+SWAPPED_ORDER = '>' if sys.byteorder == 'little' else '<'
+
+def test_as_native():
+    arr = np.arange(5) # native
+    assert_equal(arr.dtype.byteorder, '=')
+    narr = as_native_array(arr)
+    assert_true(arr is narr)
+    sdt = arr.dtype.newbyteorder('s')
+    barr = arr.astype(sdt)
+    assert_equal(barr.dtype.byteorder, SWAPPED_ORDER)
+    narr = as_native_array(barr)
+    assert_false(barr is narr)
+    assert_array_equal(barr, narr)
+    assert_equal(narr.dtype.byteorder, NATIVE_ORDER)
+