[jira] [Created] (TIKA-1430) CHM parser gets faulty text (fix found)

["Bin Hawking (JIRA)" <ji...@apache.org>]

Bin Hawking created TIKA-1430:
---------------------------------

             Summary: CHM parser gets faulty text (fix found)
                 Key: TIKA-1430
                 URL: https://issues.apache.org/jira/browse/TIKA-1430
             Project: Tika
          Issue Type: Bug
          Components: parser
    Affects Versions: 1.6, 1.5
         Environment: Windows 7; JDK 7 or 8
            Reporter: Bin Hawking
            Priority: Critical


Get partially wrong text out of a CHM file, including the chm files in tika-parsers/src/test/resources/test-documents/testChm*.chm

I tried 1.6 and 1.5. Same bad. I wonder why no one complained before? 

I checked the source code. The cause is obvious:

When tika decompresses the LZX, the first block is done well, but as to the 2nd block and later on, Tika uses previous content as the compressed data. see in org.apache.tika.parser.chm.lzx.ChmLzxBlock

"""
                if (prevBlock != null
                        && prevBlock.getState().getBlockLength() > prevBlock
                                .getState().getBlockRemaining())
                    setChmSection(new ChmSection(prevBlock.getContent()));
//                   NOTE: the dataSegment to be decompressed is not kept
                else
                    setChmSection(new ChmSection(dataSegment));
"""

My fix:
1.	Add a prevcontent member variable in ChmSection class, so that dataSegment and prevBlock.getContent() are both kept in it.
2.	In ChmLzxBlock.extractContent() when invoking decompressVerbatimBlock(), pass ChmSection.prevcontent if exists, instead of ChmSection.data.

Now, I try some chm files, and got the correct texts.

BTW. The unit test should be tougher, as in this case some small text (the first block) is decompressed correctly.




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