Re: [boost] [RFC] string inserter/extractor "q u o t i n g"

Subject: Re: [boost] [RFC] string inserter/extractor "q u o t i n g"
From: Dmitry Goncharov (dgoncharov_at_[hidden])
Date: 2010-06-23 12:06:54

> -----Original Message-----
> From: boost-bounces_at_[hidden] [mailto:boost-
> bounces_at_[hidden]] On Behalf Of Eric Niebler
> Sent: Wednesday, June 23, 2010 7:49 PM
> To: boost_at_[hidden]
> Subject: Re: [boost] [RFC] string inserter/extractor "q u o t i n g"
> 
> > Do you think uri escaping (reserved chars are replaced with %hexdigit
> hexdigit) should be supported as well?
> 
> By this utility? No. By another string algorithm? Yeah, maybe. Could be useful
> for both filesystem and asio.
I am not sure how this can be useful for filesystem.

> What's your use case?
Uri parsing.
I found out that it was easier to implement this unescaping with a function rather than with a grammar parser.
I am attaching an implementation of uri_unescape().

BR, Dmitry

std::string uri_unescape(std::string const& s)
{
    std::string result;
    result.reserve(s.size());
    size_t cur = 0;
    size_t prev = 0;
    size_t const npos = std::string::npos;
    while ((cur = s.find('%', prev)) != npos)
    {
        if (s.size() < cur + 3 || !isxdigit(s[cur + 1]) || !isxdigit(s[cur + 2]))
            return std::string();
        result += s.substr(prev, cur - prev);
        char b[3];
        b[0] = s[cur + 1];
        b[1] = s[cur + 2];
        b[2] = 0;
        char const c = static_cast<char>(strtoul(b, 0, 16));
        result += c;
        prev = cur + 3;
    }
    result += s.substr(prev);
    return result;
}