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https://issues.apache.org/jira/browse/FLINK-10134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16620859#comment-16620859
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ASF GitHub Bot commented on FLINK-10134:
----------------------------------------

XuQianJin-Stars commented on issue #6710: [FLINK-10134] UTF-16 support for 
TextInputFormat bug fixed
URL: https://github.com/apache/flink/pull/6710#issuecomment-422881621
 
 
   > Hi @XuQianJin-Stars , thanks for your PR. Could you rebase your commits?
   
   @Clarkkkkk Thank you. I have re submitted PR. You can help me check my PR 
and give you advice.

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> UTF-16 support for TextInputFormat
> ----------------------------------
>
>                 Key: FLINK-10134
>                 URL: https://issues.apache.org/jira/browse/FLINK-10134
>             Project: Flink
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.4.2
>            Reporter: David Dreyfus
>            Priority: Blocker
>              Labels: pull-request-available
>
> It does not appear that Flink supports a charset encoding of "UTF-16". It 
> particular, it doesn't appear that Flink consumes the Byte Order Mark (BOM) 
> to establish whether a UTF-16 file is UTF-16LE or UTF-16BE.
>  
> TextInputFormat.setCharset("UTF-16") calls DelimitedInputFormat.setCharset(), 
> which sets TextInputFormat.charsetName and then modifies the previously set 
> delimiterString to construct the proper byte string encoding of the the 
> delimiter. This same charsetName is also used in TextInputFormat.readRecord() 
> to interpret the bytes read from the file.
>  
> There are two problems that this implementation would seem to have when using 
> UTF-16.
>  # delimiterString.getBytes(getCharset()) in DelimitedInputFormat.java will 
> return a Big Endian byte sequence including the Byte Order Mark (BOM). The 
> actual text file will not contain a BOM at each line ending, so the delimiter 
> will never be read. Moreover, if the actual byte encoding of the file is 
> Little Endian, the bytes will be interpreted incorrectly.
>  # TextInputFormat.readRecord() will not see a BOM each time it decodes a 
> byte sequence with the String(bytes, offset, numBytes, charset) call. 
> Therefore, it will assume Big Endian, which may not always be correct. [1] 
> [https://github.com/apache/flink/blob/master/flink-java/src/main/java/org/apache/flink/api/java/io/TextInputFormat.java#L95]
>  
> While there are likely many solutions, I would think that all of them would 
> have to start by reading the BOM from the file when a Split is opened and 
> then using that BOM to modify the specified encoding to a BOM specific one 
> when the caller doesn't specify one, and to overwrite the caller's 
> specification if the BOM is in conflict with the caller's specification. That 
> is, if the BOM indicates Little Endian and the caller indicates UTF-16BE, 
> Flink should rewrite the charsetName as UTF-16LE.
>  I hope this makes sense and that I haven't been testing incorrectly or 
> misreading the code.
>  
> I've verified the problem on version 1.4.2. I believe the problem exists on 
> all versions. 



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