gistfile1.txt

    subrange(
        basic_multi_buffer const& b,
        size_type pos,
        size_type n) noexcept
    {
        pos = pos + b.in_pos_;
        auto it = b_->list_.begin();
        for(;;)
        {
            if(it == b_->list_.end())
            {
                begin_ = it;
                end_ = it;
                begin_pos_ = 0;
                end_pos_ = 0;
                return;
            }
            if(it->size() > pos)
            {
                begin_ = it;
                begin_pos_ = pos;
                break;
            }
            pos -= it->size();
            ++it;
        }
        BOOST_ASSERT(
            it != b_->list_.end());
        auto const last = std::prev(
            b_->list_.end());
        if(it == last)
        {
            end_ = it;
            if(it == b_>list_.begin())
            {
                auto const avail =
                    b_->out_end_ - b_->in_pos_;
                if(n >= avail)
                    end_pos_ = b_->out_end_;
                else
                    end_pos_ = begin_pos_ + n;
            }
            else
            {
                auto const avail =
                    b_->out_end_;
                if(n >= avail)
                    end_pos_ = avail;
                else
                    end_pos_ = n;
            }
            return;
        }
        ++it;
        while(it != last)
        {
            if(it == b_->list_.end())
            {
                end_ = it;
                end_pos_ = 0;
                return;
            }
            auto size = it->size();
            if(n < size)
            {
                end_ = it;
                end_pos_ = n;
                return;
            }
            n -= size;
            ++it;
        }
        BOOST_ASSERT(
            it != b_->list_.end());
        end_ = it;
        auto const avail =
            b_->out_end_;
        if(n >= avail)
            end_pos_ = avail;
        else
            end_pos_ = n;
    }