Saving large table FITS may lead to a truncated file

CHANGES.rst

@@ -873,6 +873,9 @@ Bug Fixes
 
 - ``astropy.io.fits``
 
+  - Fixed a regression that could cause writes of large FITS files to be
+    truncated. [#4307]
+
 - ``astropy.io.misc``
 
 - ``astropy.io.registry``

astropy/io/fits/hdu/base.py

@@ -14,8 +14,7 @@
 from ..file import _File
 from ..header import Header, _pad_length
 from ..util import (_is_int, _is_pseudo_unsigned, _unsigned_zero,
-                    itersubclasses, decode_ascii,
-                    _get_array_mmap, _array_to_file, first)
+                    itersubclasses, decode_ascii, _get_array_mmap, first)
 from ..verify import _Verify, _ErrList
 
 from ....extern.six import string_types, add_metaclass
@@ -727,7 +726,7 @@ def _writedata_direct_copy(self, fileobj):
 
         raw = self._get_raw_data(self._data_size, 'ubyte', self._data_offset)
         if raw is not None:
-            _array_to_file(raw, fileobj)
+            fileobj.writearray(raw)
             return raw.nbytes
         else:
             return 0

astropy/io/fits/util.py

@@ -2,6 +2,7 @@
 
 from __future__ import division
 
+import errno
 import gzip as _system_gzip
 import itertools
 import io
@@ -862,6 +863,7 @@ def _write_string(f, s):
     elif isinstance(f, StringIO) and isinstance(s, np.ndarray):
         # Workaround for StringIO/ndarray incompatibility
         s = s.data
+
     f.write(s)