Re: [HPACK]Looking for huffman frequency tables

On Fri, Mar 07, 2014 at 10:03:29AM +0530, Ashok Kumar wrote:
> Hi, I'm unable to find the huffman frequency tables for any of the drafts.
> Is this available somewhere?

Some very old expired drafts about header compression (not HPACK) might have
that data (assuming the tables haven't been tweaked).

Other than that, I don't think the frequencies are documented anywhere.

> I'm not entirely clear on how to generate the
> huffman tree with the codes already given.

You don't really need to:

Each entry explicitly gives the bit sequence coding each symbol.
The string encoding is concatenation of those, followed by however
many set bits (it is specified to pad with EOS, but first 7 bits of
EOS are currently all ones) required to reach next octet boundary.

E.g. ABC is:

1101111 11101011 11101100 1 
=> DF D7 D9

1 padding bit.

And abc is:

01000 101111 01001  (2 octets)
=> 45 E9

The string happens to end on octet boundary, so no padding.

-Ilari

Received on Friday, 7 March 2014 05:00:26 UTC