test

    std::vector<char> buf;

    buf.reserve(64);

    bool seen_nonws = false;

    bool last_was_space = false;

    // A whitespace run always collapses to exactly one space, whether it's

    // leading, internal, trailing, or the entire run -- never to zero. A

    // leading run is just as significant as an internal one: it's what

    // separates this text from whatever inline element preceded it (e.g.

    // "</span> next word", or two adjacent elements separated only by

    // whitespace like "<a>A</a> <a>B</a>"). Dropping it silently glues

    // words together in the rendered output.

    size_t i = start;

    while (i < in.size()) {

        char c = in[i];

        }

        if (c == ' ' || c == '\t' || c == '\r' || c == '\n') {

            if (seen_nonws) {

            if (!last_was_space) {

                buf.push_back(' ');

                last_was_space = true;

            }

            }

            ++i;

            continue;

        }

        buf.push_back(c);

        seen_nonws = true;

        last_was_space = false;

        ++i;

    }