+function room_mt:get_historylength()
+ return self._data.history_length or default_history_length;
+end
+function room_mt:set_historylength(length)
+ length = math.min(tonumber(length) or default_history_length, max_history_length or math.huge);
+ if length == default_history_length then
+ length = nil;
+ end
+ self._data.history_length = length;
+end
+
+
+local function construct_stanza_id(room, stanza)
+ local from_jid, to_nick = stanza.attr.from, stanza.attr.to;
+ local from_nick = room._jid_nick[from_jid];
+ local occupant = room._occupants[to_nick];
+ local to_jid = occupant.jid;
+
+ return from_nick, to_jid, base64.encode(to_jid.."\0"..stanza.attr.id.."\0"..md5(from_jid));
+end
+local function deconstruct_stanza_id(room, stanza)
+ local from_jid_possiblybare, to_nick = stanza.attr.from, stanza.attr.to;
+ local from_jid, id, to_jid_hash = (base64.decode(stanza.attr.id) or ""):match("^(.+)%z(.*)%z(.+)$");
+ local from_nick = room._jid_nick[from_jid];
+
+ if not(from_nick) then return; end
+ if not(from_jid_possiblybare == from_jid or from_jid_possiblybare == jid_bare(from_jid)) then return; end
+
+ local occupant = room._occupants[to_nick];
+ for to_jid in pairs(occupant and occupant.sessions or {}) do
+ if md5(to_jid) == to_jid_hash then
+ return from_nick, to_jid, id;
+ end
+ end
+end
+