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Bug #53854 Missing constants for compression type.
Submitted: 2011-01-27 14:54 UTC Modified: 2011-01-31 15:16 UTC
Votes:1
Avg. Score:3.0 ± 0.0
Reproduced:0 of 0 (0.0%)
From: rquadling@php.net Assigned: aharvey
Status: Assigned Package: Zip Related
PHP Version: 5.3SVN-2011-01-27 (SVN) OS: n/a
Private report: No CVE-ID:
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 [2011-01-27 14:54 UTC] rquadling@php.net
Description:
------------
ext/zip internally uses several constants to identify the nature of the compressed 
content.

Not all of these are exposed, though one of them is documented 
(ZipArchive::CM_BZIP2).

The attached patch for ext/zip/php_zip.c adds the missing constants.

Once this is committed, I can update the documentation with the others (LZMA, 
TERSE, LZ77, WAVPACK and PPMD).


Patches

missing_zip_constants.patch (last revision 2011-01-27 13:55 UTC) by rquadling@php.net)

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 [2011-01-27 14:55 UTC] rquadling@php.net
The following patch has been added/updated:

Patch Name: missing_zip_constants.patch
Revision:   1296136529
URL:        http://bugs.php.net/patch-display.php?bug=53854&patch=missing_zip_constants.patch&revision=1296136529
 [2011-01-28 00:49 UTC] aharvey@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: aharvey
 [2011-01-28 05:19 UTC] aharvey@php.net
Automatic comment from SVN on behalf of aharvey
Revision: http://svn.php.net/viewvc/?view=revision&revision=307807
Log: Fixed bug #53854 (Missing constants for compression type). Patch by Richard
Quadling.
 [2011-01-28 05:19 UTC] aharvey@php.net
-Status: Assigned +Status: Closed
 [2011-01-28 05:19 UTC] aharvey@php.net
This bug has been fixed in SVN.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.


 [2011-01-28 07:43 UTC] pajoye@php.net
-Status: Closed +Status: Assigned
 [2011-01-28 07:43 UTC] pajoye@php.net
Are you sure all compression modes are implemented? I don't think they are, afair 
that's also why I did not add them.
 [2011-01-28 11:22 UTC] rquadling@php.net
As the compression mechanisms are stored within the zip file itself, it isn't 
necessarily a requirement for php_zip to support compression/decompression of these 
types, just identification.

Using WinZip V15.0, I've created an archive with CM_PPMD, CM_LZMA, CM_BZIP and 
CM_WAVPACK compressions.

Still looking for LZ77 and Terse.

The compression types are correctly identified by php_zip, so having the constants 
makes sense to me.

I'll update the documentation to say that whilst identification of these types is 
performed, compression and decompression of these types is not currently supported.
 [2011-01-28 11:34 UTC] pajoye@php.net
If they are not implemented, no, it does not make sense to have them exposed. If 
one uses them he will then expect the compression mode to be set and used 
accordingly.

However for reading archive and get information about a given compression mode, 
yes. But only if they are actually used and set by libzip. If not, please revert 
this change.
 [2011-01-28 12:03 UTC] rquadling@php.net
I took a file (an uncompressed WAV file) and compressed it using WinZip V15 using different algorithms.

Using the following code ...

<?php
$zip = new ZipArchive;
$zip->open('wav.zipx');
foreach(range(0, $zip->numFiles - 1) as $index) {
	print_r($stat = $zip->statIndex($index));
	$zip->extractTo('.', array($stat['name']));
	echo $zip->getStatusString(), PHP_EOL;
}
$zip->close();


Outputs ...

Array
(
    [name] => WavPack.wav
    [index] => 0
    [crc] => 1384274557
    [size] => 154826
    [mtime] => 1296208410
    [comp_size] => 45366
    [comp_method] => 97
)
Compression method not supported
Array
(
    [name] => PPMD.wav
    [index] => 1
    [crc] => 1384274557
    [size] => 154826
    [mtime] => 1296208410
    [comp_size] => 100729
    [comp_method] => 98
)
Compression method not supported
Array
(
    [name] => LZMA.wav
    [index] => 2
    [crc] => 1384274557
    [size] => 154826
    [mtime] => 1296208410
    [comp_size] => 68162
    [comp_method] => 14
)
Compression method not supported
Array
(
    [name] => BZIP2.wav
    [index] => 3
    [crc] => 1384274557
    [size] => 154826
    [mtime] => 1296208410
    [comp_size] => 104633
    [comp_method] => 12
)
Compression method not supported


As you can see, 98, 97, 14 and 12 are all identified as the comp_method (correctly). None of these compression methods are supported by php_zip, but the constants should be present to allow determination of the method used.

Interestingly WavPack was the best algorithm to use on uncompressed audio (which WinZip performed when I asked it to "compress to the smallest size").

I can send the zip file if needed (300K).

I think it is important to remember that the zip files being accessed by php_zip may not have been produced by php_zip.
 [2011-01-28 12:06 UTC] pajoye@php.net
That's what I asked. We can keep them only and only if libzip detects AND uses 
these compression types correctly. It seems to be the case. Can you confirm it and 
maybe add a test per compression method?
 [2011-01-28 12:11 UTC] rquadling@php.net
Just as an aside, the error constants that ARE documented ... I can see no way to 
generate them. None of the methods or functions in php_zip return an error 
constant. Should these be removed?
 [2011-01-28 12:27 UTC] pajoye@php.net
Let try to keep this discussion sane...:

We can keep them only if it is supported at least to read the information about 
an entry. For example, if an entry uses LZ77, then doing a stat/reading the info 
MUST return CW_LZ77.

If that's not the case, then we must remove them as it makes no sense to expose 
them to the user.

Is it more clear now? :)
 [2011-01-31 15:16 UTC] rquadling@php.net
I've built a zip file containing the following compression methods (the table below shows the value, the constant name and ZipArchive::getStatusString()'s output when decompression is attempted and fails) :

0  : CM_STORE          : Decompression supported.
1  : CM_SHRINK         : Compression method not supported.
6  : CM_IMPLODE        : Compression method not supported.
8  : CM_DEFLATE        : Decompression supported.
9  : CM_DEFLATE64      : Compression method not supported.
10 : CM_PKWARE_IMPLODE : Compression method not supported.
12 : CM_BZIP2          : Compression method not supported.
14 : CM_LZMA           : Compression method not supported.
97 : CM_WAVPACK        : Compression method not supported.
98 : CM_PPMD           : Compression method not supported.

I cannot find any app that will create a ZIP file using the following compression methods.

2  : CM_REDUCE_1
3  : CM_REDUCE_2
4  : CM_REDUCE_3
5  : CM_REDUCE_4
18 : CM_TERSE
19 : CM_LZ77

I have Terse (Hercules app) and LZ77 (I think this is the Microsoft Compress format), but they do not create .ZIP files and the files magic-bytes are not zip related - so you can't just call the file a .zip file and get away with it.

I've got nowhere with REDUCE.

I've got a zip file and .phpt test to cover the compression methods I have found.

Given what I've found so far, I'm guessing that php_zip only really supports storing and deflating/inflating. The constants for the compression methods that I've managed to test should be exposed.

Those that I've not should be removed be unexposed and removed from the documentation.

But I'd like to add to the docs something along the lines of "Other compression methods may exist."

Richard.
 
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