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From "Lasse Collin (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COMPRESS-146) BZip2CompressorInputStream always treats 0x177245385090 as EOF, but should treat this as EOS
Date Tue, 08 Nov 2011 10:22:51 GMT

    [ https://issues.apache.org/jira/browse/COMPRESS-146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13146202#comment-13146202
] 

Lasse Collin commented on COMPRESS-146:
---------------------------------------

The danger is that when you have compressed data inside another file format, you want the
decompressor to stop after it has decompressed one compressed stream. For example, if you
have bzip2 data in a .zip file, the decompressor must stop after the first stream or things
will go wrong.

If the default is changed, a few applications that need the above feature (I don't know if
there actually are any) will break badly. At the same time it would fix many other applications
that handle standalone .gz or .bz2 files and thus should support concatenated streams. Since
concatenated streams aren't very common, many don't know that their application has such a
bug.

Maybe the default should be changed in Compress 2.0, if API changes are OK at that point.
Or maybe the single-argument constructor should be marked as deprecated so that it creates
a warning at compile time, which should hopefully make people notice that there's a new two-argument
constructor.
                
> BZip2CompressorInputStream always treats 0x177245385090 as EOF, but should treat this
as EOS
> --------------------------------------------------------------------------------------------
>
>                 Key: COMPRESS-146
>                 URL: https://issues.apache.org/jira/browse/COMPRESS-146
>             Project: Commons Compress
>          Issue Type: Bug
>          Components: Compressors
>         Environment: all
>            Reporter: Dmitriy Smirnov
>            Priority: Critical
>              Labels: 0x177245385090
>             Fix For: 1.4
>
>         Attachments: bzip2-concatenated.patch
>
>   Original Estimate: 4h
>  Remaining Estimate: 4h
>
> BZip2CompressorInputStream always treats 0x177245385090 as EOF, but should treat this
as EOS
> This error occurs mostly on large size files as sudden EOF somwere in the middle of the
file.
> An example of data from archived file:
> $ cat fastq.ax.bz2 | od -t x1 | grep -A 1 '17 72 45'
> 22711660 d0 ff b6 01 20 10 ff ff 17 72 45 38 50 90 2e ff
> 22711700 b2 d3 42 5a 68 39 31 41 59 26 53 59 84 3c 41 75
> --
> 24637020 c5 49 ff 19 80 49 20 7f ff 17 72 45 38 50 90 a4
> 24637040 a8 ac bd 42 5a 68 39 31 41 59 26 53 59 0d 9a b4
> --
> 40302720 ff b1 24 80 10 ff ff 17 72 45 38 50 90 24 cb c5
> 40302740 90 42 5a 68 39 31 41 59 26 53 59 42 05 ae 5e 05
> .....
> Suggested solution:
>     private void initBlock() throws IOException {
>         char magic0 = bsGetUByte();
>         char magic1 = bsGetUByte();
>         char magic2 = bsGetUByte();
>         char magic3 = bsGetUByte();
>         char magic4 = bsGetUByte();
>         char magic5 = bsGetUByte();
>         if( magic0 == 0x17 && magic1 == 0x72 && magic2 == 0x45
>             && magic3 == 0x38 && magic4 == 0x50 && magic5 ==
0x90 ) 
>           
>         {
>         	if( complete() ) // end of file);
>         	{
>         		return;
>         	} else
>         	{
>         		magic0 = bsGetUByte();
>                 magic1 = bsGetUByte();
>                 magic2 = bsGetUByte();
>                 magic3 = bsGetUByte();
>                 magic4 = bsGetUByte();
>                 magic5 = bsGetUByte();
>         	}
>         } 
>         if (magic0 != 0x31 || // '1'
>                    magic1 != 0x41 || // 'A'
>                    magic2 != 0x59 || // 'Y'
>                    magic3 != 0x26 || // '&'
>                    magic4 != 0x53 || // 'S'
>                    magic5 != 0x59 // 'Y'
>                    ) {
>             this.currentState = EOF;
>             throw new IOException("bad block header");
>         } else {
>             this.storedBlockCRC = bsGetInt();
>             this.blockRandomised = bsR(1) == 1;
>             /**
>              * Allocate data here instead in constructor, so we do not allocate
>              * it if the input file is empty.
>              */
>             if (this.data == null) {
>                 this.data = new Data(this.blockSize100k);
>             }
>             // currBlockNo++;
>             getAndMoveToFrontDecode();
>             this.crc.initialiseCRC();
>             this.currentState = START_BLOCK_STATE;
>         }
>     }
>     private boolean 
>     complete() throws IOException 
>     { 
>     	boolean result = false;
>         this.storedCombinedCRC = bsGetInt();
>         try
>         {
>             if (in.available() == 0 ) 
>             {
>                 throw new IOException( "EOF" );
>             }
>             checkMagicChar('B', "first");
>             checkMagicChar('Z', "second");
>             checkMagicChar('h', "third");
>             int blockSize = this.in.read();
>             if ((blockSize < '1') || (blockSize > '9')) {
>                 throw new IOException("Stream is not BZip2 formatted: illegal "
>                                       + "blocksize " + (char) blockSize);
>             }
>             this.blockSize100k = blockSize - '0';
>             this.bsLive = 0;
>             this.bsBuff = 0;
>         } catch( IOException e )
>         {
>         	this.currentState = EOF;
>         	
>         	result = true;
>         }
>         
>         this.data = null;
>         if (this.storedCombinedCRC != this.computedCombinedCRC) {
>             throw new IOException("BZip2 CRC error");
>         }
>         this.computedCombinedCRC = 0;    
>         return result;
>     }

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