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

static unsigned int ustar_header_chksum(const void *buffer, int sign)
{
  const char *p = (const char *)buffer;
  unsigned int chksum = 0;
  while (p < (const char *)buffer + strlen(buffer))
  {
    if (sign) chksum += *p++; else chksum += (unsigned char)*p++;
  }
  return chksum;
}

int main(int argc, char** argv)
{
const char* teststring = "żółte źrebię";
printf("%u\n", ustar_header_chksum(teststring, 0));
printf("%u\n", ustar_header_chksum(teststring, 1));
return 0;
}