string_format.cpp

#include <sstream>
#include <iostream>
#include <cstdio>
#include <string>
#include <vector>

// To test performance you can compile with different preprocessor defines:
// g++ -std=c++11 -O2 -D USE_PRINTF string_format.cpp -o using_printf
// g++ -std=c++11 -O2 -D USE_IOSTREAM string_format.cpp -o using_iostream
// g++ -std=c++11 -O2 -D USE_STRING string_format.cpp -o using_string

// Then you can simply time multiple runs of each program:
// time using_printf
// time using_iostream
// time using_string

//On my machine the results are as follows:
//printf:   2.5 seconds
//ostream:  6.9 seconds
//string:   1.6 seconds

int main() {
    std::vector<const char*> types = { "c", "ms", "h", "g", "s"};
    std::string prefix = "foo";
    std::vector<std::string> keys = { "bar", "baz", "qux", "quux", "corge", "gorge" };

    // testing 3 ways to do string formatting for statsd like messages
    std::string buffer(256, '\0');
    bool needs_dot = true;
    for(int value =0; value < 10000000; ++value) {
        float freq = (value % 11) / 10.f;

#ifdef USE_PRINTF
         if(freq < 1.f) {
            std::snprintf(&buffer.front(),
                           buffer.size(),
                           "%s%s%s:%d|%s|@%.2f",
                           prefix.c_str(),
                           needs_dot ? "." : "",
                           keys[value % keys.size()].c_str(),
                           value,
                           types[value % types.size()],
                           freq);
         }
         else {
             std::snprintf(&buffer.front(),
                           buffer.size(),
                           "%s%s%s:%d|%s",
                           prefix.c_str(),
                           needs_dot ? "." : "",
                           keys[value % keys.size()].c_str(),
                           value,
                           types[value % types.size()]);
         }
#endif

#ifdef USE_IOSTREAM
        std::ostringstream ss;
        ss.precision(2);
        ss << prefix << (needs_dot ? "." : "")<<
            keys[value % keys.size()].c_str()<<':'<<
            value<<'|'<<
            types[value % types.size()];
        if(freq < 1.f)
            ss <<"|@"<< std::fixed << freq;
        auto str = ss.str();
#endif

#ifdef USE_STRING
        buffer.clear();
        buffer.append(prefix);
        if(needs_dot)
            buffer.push_back('.');
        buffer.append(keys[value % keys.size()]);
        buffer.push_back(':');
        buffer.append(std::to_string(value));
        buffer.push_back('|');
        buffer.append(types[value % types.size()]);
        if(freq < 1.f) {
            buffer.append("|@0.");
            buffer.append(std::to_string(static_cast<int>(freq * 100)));
        }
#endif
    }
    return 0;
}