Quick multi-line replacement

Question

I have a line like the following:

{A}jahshs{b}jwuw{c}wuqjwhaha{d}{e}{f}jsj{g}

And I need to replace each {x}with a different line. The problem arises because this process will repeat about 1000 times / second, so I need an optimized / fast way to do this.

Any idea? Boost replace? Formatting format? Etc ..

Answer 1

• predefine all buffers

  ....

• profit

Oh and no spam. Sample code in 5 to 10 minutes.

Good here: also Live On Coliru

#include <string>
#include <sstream>
#include <boost/utility/string_ref.hpp>

template <typename Range>
int expand(Range const& /*key*/)
{
    return rand()%42; // todo lookup value with key (be sure to stay lean here)
}

#include <iostream>
int main()
{
    static const std::string msg_template = "{A}jahshs{b}jwuw{c}wuqjwhaha{d}{e}{f}jsj{g}\n";

    std::ostringstream builder;
    builder.str().reserve(1024); // reserve ample room, not crucial since we reuse it anyways

    for (size_t iterations = 1ul << 14; iterations; --iterations)
    {
        builder.str("");
        std::ostreambuf_iterator<char> out(builder);

        for(auto f(msg_template.begin()), l(msg_template.end()); f != l;)
        {
            switch(*f)
            {
                case '{' : 
                    {
                        auto s = ++f;
                        size_t n = 0;

                        while (f!=l && *f != '}')
                            ++f, ++n;

                        // key is [s,f] now
                        builder << expand(boost::string_ref(&*s, n));

                        if (f!=l)
                            ++f; // skip '}'
                    }
                    break;
                default:
                    *out++ = *f++;
            }
        }
        // to make it slow, uncomment:
        // std::cout << builder.str();
    }
}

~ 0.239s . Thats about 68k expansions/second. . 4 /. Coliru 1 /.

:

• , 1 , string_ref char, '}'.
• . ( , ).