buf_remove_from_front(buf_t *buf, size_t n)
{
  tor_assert(buf->datalen >= n);
  while (n) {
    tor_assert(buf->head);
    if (buf->head->datalen > n) {
      buf->head->datalen -= n;
      buf->head->data += n;
      buf->datalen -= n;
      return;
    } else {
      chunk_t *victim = buf->head;
      n -= victim->datalen;
      buf->datalen -= victim->datalen;
      buf->head = victim->next;
      if (buf->tail == victim)
        buf->tail = NULL;
      chunk_free_unchecked(victim);
    }
  }
  check();
}
buf_remove_from_front(buf_t *buf, size_t n)
{
  tor_assert(buf->datalen >= n);
  while (n) {
    tor_assert(buf->head);
    if (buf->head->datalen > n) {
      buf->head->datalen -= n;
      buf->head->data += n;
      buf->datalen -= n;
      return;
    } else {
      chunk_t *victim = buf->head;
      n -= victim->datalen;
      buf->datalen -= victim->datalen;
      buf->head = victim->next;
      if (buf->tail == victim)
        buf->tail = NULL;
      chunk_free_unchecked(victim);
    }
  }
  check();
}