lastvisitdate->AliasYarn(mEnv, &yarn);
nsGlobalHistory::GetLastVisitDate(const char *aURL, PRInt64 *_retval){  NS_PRECONDITION(aURL != nsnull, "null ptr");  if (! aURL)    return NS_ERROR_NULL_POINTER;  nsresult rv;  mdb_err err;  PRInt32 len = PL_strlen(aURL);  mdbYarn yarn = { (void*) aURL, len, len, 0, 0, nsnull };  mdbOid rowId;  nsMdbPtr<nsIMdbRow> row(mEnv);  err = mStore->FindRow(mEnv, kToken_HistoryRowScope, kToken_URLColumn, &yarn,                        &rowId, getter_Acquires(row));  if (err != 0) return NS_ERROR_FAILURE;  if (row) {    err = row->AliasCellYarn(mEnv, kToken_LastVisitDateColumn, &yarn);    if (err != 0) return NS_ERROR_FAILURE;    rv = CharsToPRInt64((const char*) yarn.mYarn_Buf, yarn.mYarn_Fill, _retval);    if (NS_FAILED(rv)) return rv;  }  else {    *_retval = LL_ZERO; // return zero if not found  }  return NS_OK;}