Re: fsverify.py unable to fix invalid svndiff header

>>>>> Steinar Bang <sb_at_dod.no>:

>>>>> Steinar Bang <sb_at_dod.no>:
>>>>> Stefan Sperling <stsp_at_elego.de>:

>>> Try to locate boundaries of representations, which look as follows:

>>> https://svn.apache.org/repos/asf/subversion/trunk/subversion/libsvn_fs_fs/structure
>>> A representation begins with a line containing either "PLAIN\n" or
>>> "DELTA\n" or "DELTA <rev> <offset> <length>\n", where <rev>, <offset>,
>>> and <length> give the location of the delta base of the representation
>>> and the amount of data it contains (not counting the header or
>>> trailer). If no base location is given for a delta, the base is the
>>> empty stream. After the initial line comes raw svndiff data, followed
>>> by a cosmetic trailer "ENDREP\n".

>> `M-j 1916 RET', takes me here:
>> 00000770: 4e44 5245 500a 4445 4c54 410a 5356 4e01 NDREP.DELTA.SVN.
>> 00000780: 0000 8c0c 823d 8431 823b 8140 4c00 8844 .....=.1.;._at_L..D
>> 00000790: 4ca8 404e 0048 8100 bf45 820d 9945 820d L._at_N.H...E...E..
>> ...

> So... trying to interpret this with the description that Stefan gave,
> and that Daniel referred to. Here we have "DELTA\n" (the "0A" is "\n"),
> which begins a representation according to the above description.

> But this is where I get a bit lost.

Just analyzing a little bit further from the /subversion/notes/svndiff
description that Daniel mentioned.

The first part after "DELTA\n" is "SVN" followed by a one byte format
version number, in this case 0x01.

And then comes the hard part:
 After the header come one or more windows, until the document ends.
 (So the decoder must have external context indicating when there is no
 more svndiff data.)

Then comes the description of a window, and that is, as Daniel said,
probably not human readable, or even recognizable in a hex editor,
because the window may be zlib compressed (or so I understand it).

Hm... hard this is. The dark side strong in this one.
Received on 2011-05-14 21:24:54 CEST