Checking for the codestream markers to always occupy two bytes.

docs/source/detailed_installation.rst

@@ -137,8 +137,17 @@ platforms.
 Testing
 '''''''
 
-If you wish to run the tests (strongly recommended :-), you can either run them
+There are two environment variables you may wish to set before running the
-from within python as follows ... ::
+tests.  
+
+    * **OPJ_DATA_ROOT** - points to directory for OpenJPEG test data
+    * **FORMAT_CORPUS_ROOT** - points to directory for format-corpus repository  (see https://github.com/openplanets/format-corpus)
+
+Setting these two environment variables is not required, as any tests using 
+either of them will be skipped.
+
+In order to run the tests, you can either run them from within
+python as follows ... ::
 
     >>> import glymur
     >>> glymur.runtests()

glymur/codestream.py

@@ -102,7 +102,14 @@ class Codestream(object):
         while True:
 
             read_buffer = fptr.read(2)
-            marker_id, = struct.unpack('>H', read_buffer)
+            try:
+                marker_id, = struct.unpack('>H', read_buffer)
+            except struct.error:
+                # Treat this as a warning.
+                msg = "Marker had length {0} instead of expected length of 2 "
+                msg += "bytes.  Codestream parsing terminated."
+                warnings.warn(msg.format(len(read_buffer)))
+                break
 
             if marker_id == 0xff90 and header_only:
                 # Start-of-tile (SOT) means that we are out of the main header

glymur/test/test_format_corpus.py

@@ -0,0 +1,51 @@
+"""
+These tests deal with JPX/JP2/J2K images in the format-corpus repository.
+"""
+#pylint:  disable-all
+
+import os
+import sys
+
+if sys.hexversion < 0x02070000:
+    import unittest2 as unittest
+else:
+    import unittest
+
+import warnings
+
+from glymur import Jp2k
+import glymur
+
+try:
+    data_root = os.environ['FORMAT_CORPUS_ROOT']
+except KeyError:
+    data_root = None
+except:
+    raise
+
+
+@unittest.skipIf(sys.hexversion < 0x03020000,
+                 "Requires features introduced in 3.2 (assertWarns)")
+@unittest.skipIf(data_root is None,
+                 "FORMAT_CORPUS_ROOT environment variable not set")
+class TestSuite(unittest.TestCase):
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def test_balloon_trunc1(self):
+        # Has one byte shaved off of EOC marker.
+        jfile = os.path.join(data_root,
+                             'jp2k-test/byteCorruption/balloon_trunc1.jp2')
+        j2k = Jp2k(jfile)
+        with self.assertWarns(UserWarning):
+            c = j2k.get_codestream(header_only=False)
+        
+        # The last segment is truncated, so there should not be an EOC marker.
+        self.assertNotEqual(c.segment[-1].marker_id, 'EOC')
+
+if __name__ == "__main__":
+    unittest.main()