introduce buffering parameter in open()

Author: d-w-moore

irods/manager/data_object_manager.py

@@ -334,6 +334,7 @@ def open(self, path, mode,
                    returned_values = None,    # Used to update session reference, for forging more conns to same host, in irods.parallel.io_main
                    allow_redirect = True,     # This may be set to False to disallow the client redirect-to-resource.
                    **options):
+        _buffering = options.pop('_buffering',-1)
         _raw_fd_holder =  options.get('_raw_fd_holder',[])
         # If no keywords are used that would influence the server as to the choice of a storage resource,
         # then use the default resource in the client configuration.
@@ -434,10 +435,14 @@ def make_FileOpenRequest(**extra_opts):
             # access entry in irods.configuration
             auto_close = auto_close()
 
+        bufopt = {}
+        if _buffering > 0:
+            bufopt['buffer_size'] = _buffering
+
         if auto_close:
-            return ManagedBufferedRandom(raw, _session = self.sess)
+            return ManagedBufferedRandom(raw, _session = self.sess, **bufopt)
 
-        return io.BufferedRandom(raw)
+        return io.BufferedRandom(raw,**bufopt)
 
     def trim(self, path, **options):