#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <assert.h>

#define mstring(x) (x)->string
#define minit(x) { (x)->string = NULL; (x)->string_len=0; }
#define mfree(x) { if((x)->string) { free((x)->string); (x)->string=NULL; } (x)->string_len=0; }

typedef struct
{
    char *string;
    int string_len;
} mpointer;

int mprintf (mpointer * p, const char *format, ...)
{
    va_list arg;
    int len, size = 256, curlen;

    if(p->string == NULL) 
    {
        p->string=malloc(size); p->string[0] = 0;
	p->string_len = 0; curlen = 0;
    }
    else
    {
        p->string=realloc(p->string, (p->string_len + size));
	curlen = strlen(p->string);
    }
     while(1) 
    {
        va_start (arg, format);
        len = vsnprintf(p->string+curlen, size, format, arg);
	va_end (arg);
        /* Some glibc versions apparently return -1 if buffer too small */
        if(len > -1 && len < size) break;
	/* The return value doesn't include end null */
        size = ( len < 0 ? size * 2 : len + 1 );
	p->string=realloc(p->string, (p->string_len + size));
    }

    p->string_len += size;
    return len;
}


int main(int argc, char **argv)
{
    mpointer test;
    minit(&test);
    
    mprintf(&test, "Hello world\n");
    mprintf(&test, "This is a funny test\n");
    mprintf(&test, "Of an self reallocating function\n");
    mprintf(&test, "that shud work with %s\n", "variables");


    printf("This is test (%i): \n\"%s\"\n", strlen(test.string), test.string);

    mfree(&test);
    exit(0);
}