Function check

test/tests.c:7–21

size_t lineno = 0;

void check(int cond, const char *format, ...)
{
     if (!cond) {
          va_list args;
          if (lineno)
               fprintf(stderr, "FAILED at line %zd: ", lineno);
          else
               fprintf(stderr, "FAILED: ");
          va_start(args, format);
          vfprintf(stderr, format, args);
          va_end(args);
          fprintf(stderr, "\n");
          exit(1);
     }
}

size_t skipspaces(const unsigned char *buf, size_t i)
{