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From "Jens Geyer (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (THRIFT-4024) C# deserialization takes unnecessary time on list with unknown type of elements
Date Tue, 10 Jan 2017 14:48:58 GMT

    [ https://issues.apache.org/jira/browse/THRIFT-4024?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15815139#comment-15815139
] 

Jens Geyer edited comment on THRIFT-4024 at 1/10/17 2:48 PM:
-------------------------------------------------------------

Under which circumstances can we run into a unknown type? The Thrift type system is well-defined,
there should not be an unknown type at all. Can we have a test case?

{quote}
you may end up waiting for a random period of time until deserialization is completed (734707176
iterations of skipping in my case).
{quote}

What does random mean? Is that related to the number of items or why does it take 734 mio
iterations? Where does that number come from? Something must cause it. Please explain.



was (Author: jensg):
Under which circumstances can we run into a unknown type? The Thrift type system is well-defined,
there should not be an unknown type at all. Can we have a test case?

{quote}
you may end up waiting for a random period of time until deserialization is completed (734707176
iterations of skipping in my case).
{quote}

What does random mean? Is that related to the number of items or why does it take 734 mio
iterations? Where does that number come from? Please explain.


> C# deserialization takes unnecessary time on list with unknown type of elements
> -------------------------------------------------------------------------------
>
>                 Key: THRIFT-4024
>                 URL: https://issues.apache.org/jira/browse/THRIFT-4024
>             Project: Thrift
>          Issue Type: Bug
>          Components: C# - Library
>    Affects Versions: 0.10.0
>            Reporter: Michael Antipin
>            Assignee: Jens Geyer
>
> I'm using TBinaryProtocol and a simple transport that reads from a given byte array.
> C# library contains the following code in TProtocolUtil.Skip(TProtocol prot, TType type):
> {code}
> case TType.List:
> 	TList list = prot.ReadListBegin();
> 	for (int i = 0; i < list.Count; i++) {
> 		Skip(prot, list.ElementType);
> 	}
> 	prot.ReadListEnd();
> 	break;
> {code}
> The type of elements is detected in ReadListBegin(), and, as Skip() does nothing for
unknown types, the position in the binary remains the same until the for loop completes. 
> So, when you try to deserialize invalid data, and a field type happens to be detected
as TType.List, you may end up waiting for a random period of time until deserialization is
completed (734707176 iterations of skipping in my case).
> I suggest throwing an exception immediately when list elements type is unknown. May be,
it would be good to have a setting like *FailOnUnknownType*, so that Skip() will throw instead
of ignoring.



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