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https://issues.apache.org/jira/browse/FLINK-10134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16646214#comment-16646214
]
ASF GitHub Bot commented on FLINK-10134:
----------------------------------------
XuQianJin-Stars opened a new pull request #6823: [FLINK-10134] UTF-16 support
for TextInputFormat bug refixed
URL: https://github.com/apache/flink/pull/6823
## What is the purpose of the change
*(This PR is designed to solve the problem of `TextInputFormat` using UTF-16
encoding to parse files.)*
## Brief change log
*(To solve this bug, I added a file BOM header encoding check to determine
the current file encoding, so that when user-defined encoding format and file
with a BOM header encoding format conflict processing, specific changes in the
following::)*
- *I add `getBomFileCharset` function to `DelimitedInputFormat.java` to
detect the current file BOM header coding judgment, mainly `UTF-16BE`,
`UTF-16LE`, `UTF-8 with BOM header`, `UTF-32BE`, `UTF-32LE` these types,
default to `UTF-8`.*
- *I added the `bomCharset`,`fileBomCharsetMap`,`charsetStepSize` variable
to the `DelimitedInputFormat.java`, `getBomFileCharset(split)` to the `open`
method, and `getBomCharsetName` to get the
`bomCharset`,`fileBomCharsetMap`,`charsetStepSize` variable.*The file name that
has been parsed is used as the key, and the encoded value is inserted as a
value into the `fileBomCharsetMap`.
- In the `DelimitedInputFormat.java` method `getCharset()`, the encoding
logic is added to obtain the encoding of the current file. If the `bomCharset`
has a value, the charset of the current class is overwritten by the
`bomCharset` encoding. If the `bomCharset` has no value, the `charset` of the
current class is taken.
- Modify the readRecord method logic in `TextInputFormat.java`, using
`this.getCharset()`, `this.delimiterNewLinePos`,
`this.delimiterCarrageReturnPos` to support the processing of the end separator
for each line of multiple encoding formats.
## Verifying this change
*(Please pick either of the following options)*
This change is a trivial rework / code cleanup without any test coverage.
*(or)*
This change is already covered by existing tests, such as *(please describe
tests)*.
*(or)*
This change added tests and can be verified as follows:
*(example:)*
- *I added `testFileCharset` and `testFileCharsetReadByMultiSplits` to
`TextInputFormatTest`.*
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): (yes)
- The public API, i.e., is any changed class annotated with
`@Public(Evolving)`: (yes)
- The serializers: (no)
- The runtime per-record code paths (performance sensitive): (no )
- Anything that affects deployment or recovery: JobManager (and its
components), Checkpointing, Yarn/Mesos, ZooKeeper: (yes)
- The S3 file system connector: (no)
## Documentation
- Does this pull request introduce a new feature? (yes / no)
- If yes, how is the feature documented? (not applicable / docs / JavaDocs /
not documented)
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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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