Re: IPv6 address parsing

On Fri, Dec 15, 2017 at 12:22 PM, Michael Powell <[email protected]> wrote:
> On Fri, Dec 15, 2017 at 11:31 AM, Michael Powell <[email protected]> wrote:
>> On Thu, Dec 7, 2017 at 1:21 PM, Michael Powell <[email protected]> wrote:
>>> Again, I am moving beyond IPv4 into IPv6. Do I need to re-post that
>>> grammar attempt? Maybe I do at this point.
>>>
>>> _dot = ".";
>>> _col = char_(':');
>>> _col_x2 = _col >> _col;
>>>
>>> // _dec_octet = uint_parser<std::uint8_t, 10, 1, 3>();
>>>
>>> qi::rule<Iterator> _dec_octet = ... ; // Approach TBD; probably
>>> running with the IPv4 proposal discussed in earlier thread(s).
>>>
>>> qi::rule<Iterator> _ipv4_addr = _dec_octet >> repeat(3)[_dot >> _dec_octet];
>>> // or, qi::rule<Iterator> _ipv4_addr = raw[_dec_octet >> _dot >>
>>> _dec_octet >> _dot >> _dec_octet >> _dot >> _dec_octet];
>>>
>>> qi::rule<Iterator> _h16 = raw[repeat(1, 4)[hex]];
>>> // Or (?): _h16 = hex >> -(hex >> -(hex >> -hex));
>>> qi::rule<Iterator> _h16_col = _h16 >> _col;
>>> qi::rule<Iterator> _ls32 = _h16_col >> _h16 | _ipv4_addr;
>>>
>>> qi::rule<Iterator, std::string()> _ipv6_addr
>>>     = repeat(6)[_h16_col] >> _ls32
>>>     | _col_x2 >> repeat(5)[_h16_col] >> _ls32
>>>     | -(_h16) >> _col_x2 >> repeat(4)[_h16_col] >> _ls32
>>>     | -(_h16_col >> _h16) >> _col_x2 >> repeat(3)[_h16_col] >> _ls32
>>>     | -(repeat(1, 2)[_h16_col] >> _h16) >> _col_x2 >>
>>> repeat(2)[_h16_col] >> _ls32
>>>     | -(repeat(1, 3)[_h16_col] >> _h16) >> _col_x2 >> _h16_col >> _ls32
>>>     | -(repeat(1, 4)[_h16_col] >> _h16) >> _col_x2 >> _ls32
>>>     | -(repeat(1, 5)[_h16_col] >> _h16) >> _col_x2 >> _h16
>>>     | -(repeat(1, 6)[_h16_col] >> _h16) >> _col_x2
>>>     ;
>>
>> I am testing the grammar now, and it seems like to me that the
>> optional and/or repeat are not working correctly.
>>
>> For test case: prefix = pf_max_4|pf_count_1, suffix = pf_none,
>> appendix = bo_hex_2, which yields address: "6a80:9024::c7e3:4150".
>>
>> Should be matching the alternative, from the RFC grammar:
>>   / [*4(h16 ":") h16] "::"            ls32
>>
>> Or from the Qi grammar:
>>      | -(repeat(1, 4)[_h16_col] >> _h16) >> _col_x2 >> _ls32
>>
>> But gets rejected. Did not parse, or rejected the entire string.
>>
>> Perhaps repeat does not work quite as advertised?
>>
>> Thoughts? Suggestions?
>
>
> qi::rule<Iterator, std::string()> _ipv6_addr
>     = repeat(6)[_h16_col] >> _ls32
>     | _col_x2 >> repeat(5)[_h16_col] >> _ls32
>     | -(-_h16) >> _col_x2 >> repeat(4)[_h16_col] >> _ls32
>     | -(-_h16_col >> _h16) >> _col_x2 >> repeat(3)[_h16_col] >> _ls32
>     | -(-repeat(1, 2)[_h16_col] >> _h16) >> _col_x2 >>
> repeat(2)[_h16_col] >> _ls32
>     | -(-repeat(1, 3)[_h16_col] >> _h16) >> _col_x2 >> _h16_col >> _ls32
>     | -(-repeat(1, 4)[_h16_col] >> _h16) >> _col_x2 >> _ls32
>     | -(-repeat(1, 5)[_h16_col] >> _h16) >> _col_x2 >> _h16
>     | -(-repeat(1, 6)[_h16_col] >> _h16) >> _col_x2
>     ;
>
> I did identify that possibly the prefix phrase needs to be built from
> optional elements within itself.
>
> However, still not parsing.
>
> I am concerned that either Qi optional, repeat, etc, perhaps even
> alternatives, are not working quite right in this instance.
>
> Do I need to separate the alternatives here into "micro" grammars
> within themselves for this to possibly work?

Thus far, separating the more complex grammar into micro-grammars
seems to be the correct answer, the one that will work.

Not sure why the broader parent grammar doesn't work, however. Apart
from "greediness" suspicions, that is; the grammar is what it is, no?

>> Thank you!
>>
>>> qi::rule<Iterator> _start = _ipv6_addr >> eoi;
>>>
>>> Q: Notwithstanding concern over raw IPv4, does the overall Qi-based
>>> IPv6 grammar look reasonable? If not, why not?
>>>
>>> I'd like to land in a Fusion data structure something like (string >>
>>> uint16_t >> eoi), but if I can land here, that's acceptable, too:
>>> (string >> -(uint8_t >> uint8_t >>
>>> uint8_t >> uint8_t) >> uint16_t >> eoi).
>>>
>>> From what I can determine, then, raw[...] is the difference between
>>> parsed types like uint8_t and string?
>>>
>>> ref: http://www.ietf.org/rfc/rfc5954.txt, section 4.1 Resolution for
>>> Extra Colon in IPv4-Mapped IPv6 Address
>>>
>>> Constructive feedback appreciated.
>>>
>>> Untested ATM, to be fair.
>>>
>>> On Thu, Dec 7, 2017 at 1:09 PM, Seth <[email protected]> wrote:
>>>> On 07-12-17 18:21, Michael Powell wrote:
>>>>> Well, you remembered incorrectly.
>>>>
>>>> I was asking.
>>>>
>>>>> If there's a doable intermediate step of parsed individual octets, so
>>>>> be it; no problem.
>>>>
>>>> Please per-use all the parts of my answer.
>>>>
>>>> On 07-12-17 17:13, Seth wrote:
>>>>> Maybe you'll be more convinced when it's demonstrated (I think I did
>>>>> this before):
>>>>>
>>>>> https://wandbox.org/permlink/M12U5PEYcB8vnxIs
>>>>>
>>>>> It's really just ~3 lines of code changed:
>>>>>
>>>>>     using ipv4_address = std::string; // much less useful representation
>>>>>     // ....
>>>>>     addr_  = raw[ octet_ >> '.' >> octet_ >> '.' >> octet_ >> '.' >>
>>>>> octet_ ];
>>>>>
>>>>> Note now that test fails:
>>>>
>>>> It's all there.
>>>>

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