Re: IPv6 address parsing

On Fri, Dec 15, 2017 at 1:59 PM, Michael Powell <[email protected]> wrote:
> 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.

I removed the repeats, and I think I've isolated an issue that nested
optional operators do not work. i.e. -(-(-(...) ...) ...) >> ...

Which does not match the phrase I expect it to.

> 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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