[jira] [Commented] (THRIFT-4024) C# deserialization takes unnecessary time on list with unknown type of elements

["Jens Geyer (JIRA)" <ji...@apache.org>]

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

Jens Geyer commented on THRIFT-4024:
------------------------------------

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?

> 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
>
> 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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