[bind10-dev] writable datasources 3/3; API proposal

[Jelte Jansen]

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(to be added to data_source.h)

    //
    // Writable data sources
    //
    // To implement a new writable data source, subclass and overwrite
    // the 'low-level' methods. Overriding the high-level ones is
    // optional
    //


    //
    // low-level methods.
    //

    /**
     * Add an RRset to a zone. If the RRset already exists, the
     * RRs in this set are added to it.
     */
    virtual Result addRRset(isc::dns::Name* zonename, isc::dns::RRset&
rrset) = 0;

    /**
     * Delete an RRset from a zone. If the RRset in the zone contains
     * more RRs than the given one here, keep those.
     */
    virtual Result deleteRRset(isc::dns::Name* zonename,
isc::dns::RRset& rrset) = 0;

    /**
     * Returns if we have the zone and the serial number we pass is
     * higher than the serial number in the SOA record of the given
     * zone (according to serial arithmetic). Returns false otherwise.
     * (TODO: this one perhaps does not need to be overwritten as it
     * can use existing functions)
     */
    virtual bool checkSerial(isc::dns::Name* zonename, uint32_t serial) = 0;

    /**
     * Lock a zone (or database, or rrset(?). This should lock the
     * underlying backend, not this instance...
     */
    virtual void getWriteLock();
    virtual void releaseWriteLock();

    /**
     * Start a transaction. If the backend supports transactions,
     * this is just a wrapper. If not, you can either fake transactions
     * (by making this a nop), and risk data inconsistency, or
     * implement some form of transactions yourself.
     * One way to do it (if there are no threads) is to make addRRset
     * and deleteRRset so that their behaviour changes if one is 'in'
     * a transaction (by checking and storing, locking the database upon
     * commit and then performing all stored actions).
     * (TODO: perhaps we could also proved some basic defaults for
     * these, though i'm not sure)
     * start should probably error if there already is a transaction
     * running (or lock, the point here is to do batch commits, not
     * concurrency, at this level).
     */
    virtual void startTransaction() = 0;
    virtual void commitTransaction() = 0;
    virtual void rollbackTransaction() = 0;

    /**
     * Returns true if all the RRs in the given rrset are in the zone.
     * If rdatalen == 0, this will return true if there is an rrset with
     * the same name, class and type, regardless of the number and data
     * of the rrs it contains.
     */
    virtual bool containsRRset(isc::dns::Name* zonename,
isc::dns::RRset& rrset) = 0;

    /**
     * Returns true if non of the RRs in the given rrset are in the
     * zone.
     * Note that this does not mean *other* rrs can't be present with
     * the same name, class and type, unless one of the RRs in this set
     * has rdatalen=0;
     */
    virtual bool doesNotContainRRset(isc::dns::Name* zonename,
isc::dns::RRset& rrset) = 0;

    //
    // High-level functions
    //
    // These do not need to be overwritten by subclasses, but they
    // may be if there is a more efficient way to handle them
    // than the defaults.
    //

    /**
     * Drop all records for the given zone, and add all records in
     * the given RRsetList
     * (for use in loadzone and axfr)
     * TODO: what to do with loadzone for a zone that is not in any
     * data source yet? We need a way to specify where to store it...
     * (probably so that if none is given, the first writable data
     * source is used)
     */
    // TODO: in theory this one could be replaced by a deleteAllRRsets
    // function, together with replaceRRsets below. However, that
    // would probably mean we have to unlock and relock the database,
    // or not do transactions from within these functions (but start
    // and commit/rollback at the caller, which i think is counter-
    // intuitive
    virtual Result replaceZone(isc::dns::Name* zonename, RRSetList rrsets);

    /**
     * Deletes a set of RRsets, and adds another one
     * (for use in IXFR)
     */
    virtual Result replaceRRsets(isc::dns::Name* zonename, RRSetList
delete, RRSetList add);

    /**
     * Full handler for IXFR message.
     */
    virtual Result doIXFR(isc::dns::Message *msg);

    /**
     * Full handler for dynamic update message
     */
    virtual Result doUpdate(isc::dns::Message *msg);


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