Enables time info for XTCReader

pygmx/xtcio.pyx

@@ -152,7 +152,12 @@ cdef class XTCReader:
         size = xtc_stat.st_size
 
         with open(indexfile, 'rb') as fd:
-            unpacker = Unpacker(SubscriptableReader(fd))
+            unpacker = Unpacker(fd.read())
+            # first 4 * 8 bytes are used for checks, followed by N * (8 + 4) bytes of data
+            length = int((len(unpacker.get_buffer()) - 32) / 12)
+
+        if length < 0:
+            raise InvalidIndexException
 
         if unpacker.unpack_hyper() != INDEX_MAGIC:
             raise InvalidMagicException
@@ -173,6 +178,7 @@ cdef class XTCReader:
         except EOFError:
             pass
         self.has_cache = True
+        self.has_times = True
 
     def __cinit__(self):
         self.has_cache = False