# Re: HPACK, Draft 09, Integer Representation

```It looks like I'm not too familiar with the spec language after all :)
Anyway, I believe "6.1." it should be as visual as it is in
Wikipedia's article and at the same time a lot more concise.

On Fri, Aug 29, 2014 at 1:47 AM, Mark Nottingham <mnot@mnot.net> wrote:
> See:
>   https://github.com/http2/http2-spec/issues/595
>
> I tend to think we need some text to replace it... any volunteers?
>
>
> On 29 Aug 2014, at 2:12 am, Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com> wrote:
>
>>
>>
>>
>> On Fri, Aug 29, 2014 at 1:00 AM, Pavel Rappo <pavel.rappo@gmail.com> wrote:
>> > HPACK uses little endian.
>>
>> I think this difference should be mentioned explicitly.
>>
>>
>> FYI, wikipedia reference was deleted.
>> https://github.com/http2/http2-spec/commit/bd8d7688a9dd8708bae543a9abe889ea7797e139
>>
>>
>> > "I" is updated while loop:
>> >
>> >        repeat
>> >            B = next octet
>> >            I = I + (B & 127) * 2^M
>> >
>> >                      ~~~~~~~~~~~~~~~~~~~~~
>> >            M = M + 7
>> >        while B & 128 == 128
>> >
>> > So, initial "I" is not forgotten.
>>
>> Thanks, Tatsuhiro! It's indeed updated. I overlooked it.
>>
>> > "I" comes from next N bits as algorithm exactly says:
>> >
>> >
>> > decode I from the next N bits
>> >
>> > HPACK integer encoding uses specific prefix bits, which is described as N
>> > here in algorithm.
>> > So when decoding integer encoded with 7 prefix bits, decode initial "I" from
>> > next 7 bits.
>>
>> The only thing then, the meaning of "I" is different for the encoding
>> and decoding parts. Isn't it?
>> "The algorithm to represent an integer I is as follows:" and "For
>> informational purpose, the algorithm to decode an integer I is as
>> follows:". i.e. same "I" different meanings.
>>
>>
>> If integer X is encoded to some byte string B and then B is decoded to integer Y, then X should be equal to Y, so in that sense, both "I" mean same integer.
>> For decoding algorithm, "I" in the sentence you quoted means the result of the algorithm, and not just the first N bits.
>>
>> Best regards,
>> Tatsuhiro Tsujikawa
>>
>>
>>
>>
>
> --
> Mark Nottingham   https://www.mnot.net/
>
```

Received on Friday, 29 August 2014 15:11:39 UTC