Last modified: 2012-02-16 23:32:19 UTC

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Bug 34428 - PHP version of DiffHistoryBlob::patch() computes incorrect base text checksum
PHP version of DiffHistoryBlob::patch() computes incorrect base text checksum
Status: RESOLVED FIXED
Product: MediaWiki
Classification: Unclassified
History/Diffs (Other open bugs)
1.19
All All
: Unprioritized normal (vote)
: ---
Assigned To: Nobody - You can work on this!
:
Depends on:
Blocks:
  Show dependency tree / graph
 
Reported: 2012-02-16 00:34 UTC by Tim Starling
Modified: 2012-02-16 23:32 UTC (History)
1 user (show)

See Also:
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Mobile Platform: ---
Assignee Huggle Beta Tester: ---

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Description Tim Starling 2012-02-16 00:34:08 UTC 
Some revisions stored with DiffHistoryBlob in Wikimedia external storage cannot be decoded if xdiff_string_bpatch() is not available and thus the PHP port is used. Revision::getText() returns false.

The debug log shows "incorrect base checksum". If the checksum check is disabled, the revision appears to be decoded successfully. Perhaps an incorrect implementation of the adler32 checksum is at fault.
Comment 1 Tim Starling 2012-02-16 11:56:10 UTC 
LibXDiff has an incorrect implementation of Adler-32. The byte order is wrong, and the state is initialised to 0 instead of 1. 

If a string can be found for which the Adler-32 hash is zero, then that could be used to initialise mhash() or hash() to simulate LibXDiff's Adler-32.
Comment 2 Tim Starling 2012-02-16 23:32:19 UTC 
Fixed in r111701.
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