Program Listing for File gpa-formatter.h

↰ Return to documentation for file (include\instrumentation\gpa-formatter.h)

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

/*
    $ is defined as string formatter, use cases:
    std::cout << $(1) << std::endl;
    std::cout << $("%f", 1e100) << std::endl;

    $ is using TLS, so every thread (once $ used) gets own buffer.
    every $ returns copy of the string, so the same buffer is reused, and its size can only grow
    On every new $ that doesn't require bigger buffer we skip the memory allocation and thus the crt mutex
*/

namespace gpa {
namespace formatter {

class Formatter
{
    std::vector<char> mBuffer;

    Formatter()
        : mBuffer(1024)
    {
    }

public:
    static Formatter& TLSingleton()
    {
        static thread_local Formatter fmt;
        return fmt;
    }

    template<typename... Args>
    static std::string print(const char* fmt, Args... args)
    {
        std::vector<char>& buffer = Formatter::TLSingleton().mBuffer;
        while (true) {
            int res = std::snprintf(buffer.data(), buffer.size(), fmt, args...);
            if (res >= 0 && size_t(res) < buffer.size()) break;
            buffer.resize((res > 0) ? size_t(res) + 1 : buffer.size() * 2);
        }
        return buffer.data();
    }

    template<typename T>
    static std::string print(const T& val)
    {
        std::ostringstream oss;
        oss << val;
        return oss.str();
    }
};

}  // namespace formatter
}  // namespace gpa

#define $(...) gpa::formatter::Formatter::print(__VA_ARGS__)