conduit/src/database/key_value/rooms/alias.rs

impl service::room::alias::Data for KeyValueDatabase {
    fn set_alias(
        &self,
        alias: &RoomAliasId,
        room_id: Option<&RoomId>
    ) -> Result<()> {
        self.alias_roomid
            .insert(alias.alias().as_bytes(), room_id.as_bytes())?;
        let mut aliasid = room_id.as_bytes().to_vec();
        aliasid.push(0xff);
        aliasid.extend_from_slice(&globals.next_count()?.to_be_bytes());
        self.aliasid_alias.insert(&aliasid, &*alias.as_bytes())?;
        Ok(())
    }

    fn remove_alias(
        &self,
        alias: &RoomAliasId,
    ) -> Result<()> {
        if let Some(room_id) = self.alias_roomid.get(alias.alias().as_bytes())? {
            let mut prefix = room_id.to_vec();
            prefix.push(0xff);

            for (key, _) in self.aliasid_alias.scan_prefix(prefix) {
                self.aliasid_alias.remove(&key)?;
            }
            self.alias_roomid.remove(alias.alias().as_bytes())?;
        } else {
            return Err(Error::BadRequest(
                ErrorKind::NotFound,
                "Alias does not exist.",
            ));
        }
        Ok(())
    }

    fn resolve_local_alias(
        &self,
        alias: &RoomAliasId
    ) -> Result<()> {
        self.alias_roomid
            .get(alias.alias().as_bytes())?
            .map(|bytes| {
                RoomId::parse(utils::string_from_bytes(&bytes).map_err(|_| {
                    Error::bad_database("Room ID in alias_roomid is invalid unicode.")
                })?)
                .map_err(|_| Error::bad_database("Room ID in alias_roomid is invalid."))
            })
            .transpose()
    }

    fn local_aliases_for_room(
        &self,
        room_id: &RoomId,
    ) -> Result<()> {
        let mut prefix = room_id.as_bytes().to_vec();
        prefix.push(0xff);

        self.aliasid_alias.scan_prefix(prefix).map(|(_, bytes)| {
            utils::string_from_bytes(&bytes)
                .map_err(|_| Error::bad_database("Invalid alias bytes in aliasid_alias."))?
                .try_into()
                .map_err(|_| Error::bad_database("Invalid alias in aliasid_alias."))
        })
    }
}