[cifs-protocol] [EXTERNAL] RE: [REG:120060621000848] [MS-XCA] L77+Huffman negative huffman symbol update

Jeff McCashland jeffm at microsoft.com
Tue Jun 9 17:08:43 UTC 2020

Hi Aurélien,

I will investigate further and let you know what I find. 

Best regards,
Jeff McCashland | Senior Escalation Engineer | Microsoft Protocol Open Specifications Team 
Phone: +1 (425) 703-8300 x38300 | Hours: 9am-5pm | Time zone: (UTC-08:00) Pacific Time (US and Canada)
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We value your feedback.  My manager is Jeremy Chapman (jeremyc), +1 (469) 775-2475

-----Original Message-----
From: Aurélien Aptel <aaptel at suse.com> 
Sent: Tuesday, June 9, 2020 3:29 AM
To: Jeff McCashland <jeffm at microsoft.com>; cifs-protocol at lists.samba.org
Cc: support <support at mail.support.microsoft.com>
Subject: [EXTERNAL] RE: [REG:120060621000848] [MS-XCA] L77+Huffman negative huffman symbol update

Jeff McCashland <jeffm at microsoft.com> writes:
> It appears this section of pseudocode was added as part of an update 
> to document handling when input data > 64kb. The algorithm takes two 
> passes over the data for each 64k block in succession, first to do
> LZ77 compression, then another pass to do Huffman encoding. When both 
> passes are complete, it moved on to the next 64k block.

I understand that part. But my question was more about the details of Huffman decoding. How can HuffmanSymbol be negative if the decode table entries are all positive?

It seems to me either:
- the code building the DecodeTable wasn't updated to match the decoding
- or there is a bug in the decoding code

Aurélien Aptel / SUSE Labs Samba Team
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