#include <stdio.h>
#include <string>
#include <cassert>
#include <cstdarg>

using namespace std;

    string vstrf(const char *format, va_list argPtr) {
        static size_t  buf_size = 16;
        static char   *buffer   = new char[buf_size];

        size_t length;
        while (1) {
            if (!buffer) {
                assert(buffer); // to stop when debugging
                return "<alloc problem>";
            }

            length = vsnprintf(buffer, buf_size, format, argPtr);
            if (length < buf_size) break; // string fits into current buffer

            // otherwise resize buffer :
            buf_size += buf_size/2;
            // fprintf(stderr, "Reallocating vstrf-buffer to size=%u\n", buf_size);
            delete [] buffer;
            buffer    = new char[buf_size];
        }

        return string(buffer, length);
    }

string strf(const char *format, ...)
{
    va_list argPtr;
    va_start(argPtr, format);
    string result = vstrf(format, argPtr);
    va_end(argPtr);

    return result;
}

string strf2(const char *format, ...) {
    static size_t  buf_size = 512;
    static char   *buffer   = new char[buf_size];
    
    va_list argPtr;
    size_t length;

    while (true) {
        if (!buffer) {
            assert(buffer); // to stop when debugging
            return "<alloc problem>";
        }

        va_start(argPtr, format);
        length = vsnprintf(buffer, buf_size, format, argPtr);
        va_end(argPtr);
        
        if (length >= 0 && length < buf_size - 1) 
            // string fits into current buffer
            return std::string(buffer, length);

        // otherwise resize buffer :
        buf_size *= 2;
//        fprintf(stderr, "Reallocating vstrf-buffer to size=%u\n", buf_size);
        delete [] buffer;
        buffer = new char[buf_size];
    }
}

#define FOO "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

int main(int argc, char** argv) {
	fprintf(stderr, "Trying new strf function.\n");
	strf2("%s%s%s",FOO FOO FOO FOO, FOO FOO FOO FOO, FOO FOO FOO FOO);
	fprintf(stderr, "New function completed successfully.\n");
	fprintf(stderr, "Trying old strf function.\n");
	strf("%s%s%s",FOO FOO FOO FOO, FOO FOO FOO FOO, FOO FOO FOO FOO);
	fprintf(stderr, "Old function completed successfully.\n");
}