static inline size_t
frem(FILE * fp)
{
  fseek(fp, 0, SEEK_END);
  return ftell(fp);
}

static char *
slurp(const char * fn, size_t * rlen)
{
  size_t len;
  FILE * fp = fopen(fn, "r");
  char * buf;
  if (!fp)
  { PERROR_RETURN("fopen", NULL); }
  if (!(buf = (char *) malloc((len = frem(fp)))))
  { PERROR_RETURN("malloc", NULL); }
  rewind(fp);
  if (len != fread(buf, 1, len, fp))
  {
    free(buf);
    { PERROR_RETURN("fopen", NULL); }
  }
  *rlen = len;
  return buf;
}