Fix for #73944 bug

[wapmorgan]

Original thread: https://bugs.php.net/bug.php?id=73944

Description:

I'm writing an unpacker of MSZIP blocks that use deflate compression.
I faced a problem and created a question on stackoverflow (http://stackoverflow.com/questions/41653663/is-there-something-special-in-windows-mszip-format-or-cfdata-in-cab-files), where maintainer of zlib library adviced to use dictionary option to pass raw uncompressed data of previous block to decompress next block of data. But in fact that this option doesn't work correctly in php.

Test script:

$in = inflate_init(ZLIB_ENCODING_RAW, array('dictionary' => str_repeat("\00", 32768)));
$a = inflate_add($in, file_get_contents('https://github.com/wapmorgan/CabArchive/releases/download/0.0.1-dev/1block'));
echo '1 block: '.strlen($a).PHP_EOL;

$in = inflate_init(ZLIB_ENCODING_RAW, array('dictionary' => $a));
$b = inflate_add($in, file_get_contents('https://github.com/wapmorgan/CabArchive/releases/download/0.0.1-dev/2block'));
echo '2 block: '.($b === false ? 'failed' : strlen($b)).PHP_EOL;

Expected result:

1 block: 32768
2 block: 32768

Actual result:

1 block: 32768
Warning: inflate_add(): data error in ...
2 block: failed

What I've done

1. Removed check of dictionary parameter in inflate_add if it's a string. As told Mark Adler

a deflate dictionary is just a bunch of bytes

2. Set of dictionary in inflate_init if compression method is raw.
   If used raw method, Z_NEED_DICT will not be returned so php will not use dictionary at all.

Result after this patch, applied to master

1 block: 32768
2 block: 32768

[sgolemon]

Could you clarify what the 1block and 2block files are? To properly accept this patch we should include a unit test demonstrating what's wrong. While you did include a test with expected and actual output, the data files are... fairly opaque. Can you describe how they are created?

[wapmorgan]

These files are MSZip. They can be found in any .cab file using MSZip compression.
Example of file attached.
webrec.cab.zip
More information about MSZip format in my question on stackoverflow.

[nikic]

Can you please add your test-case from the PR description as a phpt test?

@bwoebi You might want to review this.

[bwoebi]

That looks pretty much fine, I can merge that with a phpt test attached.

[wapmorgan]

Can I include these raw files 1block and 2block in test or tests should not contain binary files?

[bwoebi]

It's totally fine to add fixture files as needed.

[wapmorgan]

Where I should put fixtures and what names it should have?

[wapmorgan]

Ok, I've added test to ext/zlib/tests as bug73944.phpt, bug73944_fixture1 and bug73944_fixture2.

[nikic]

Looks like this got merged into 7.0+ as cd1869b yesterday, so closing here.