NS_ENSURE_TRUE(mAddrInfo, NS_ERROR_NOT_AVAILABLE);
nsDNSRecord::GetNextAddr(PRUint16 port, PRNetAddr *addr){    NS_ENSURE_TRUE(mAddrInfo, NS_ERROR_NOT_AVAILABLE);    // not a programming error to poke the DNS record when it has    // no more entries.  just silently fail.  this enables consumers    // to enumerate the DNS record without calling HasMore.    if (mDone)        return NS_ERROR_NOT_AVAILABLE;    mIter = PR_EnumerateAddrInfo(mIter, mAddrInfo->get(), port, addr);    mDone = !mIter;    return NS_OK; }