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@@ -15,9 +15,11 @@
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#ifndef __ZONE_H
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#define __ZONE_H 1
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-#include <datasrc/result.h>
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+#include <dns/rrset.h>
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#include <dns/rrsetlist.h>
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+#include <datasrc/result.h>
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+
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namespace isc {
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namespace datasrc {
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@@ -224,8 +226,225 @@ typedef boost::shared_ptr<ZoneFinder> ZoneFinderPtr;
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/// \brief A pointer-like type pointing to a \c ZoneFinder object.
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typedef boost::shared_ptr<const ZoneFinder> ConstZoneFinderPtr;
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-}
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-}
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+/// The base class to make updates to a single zone.
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+///
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+/// On construction, each derived class object will start a "transaction"
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+/// for making updates to a specific zone (this means a constructor of
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+/// a derived class would normally take parameters to identify the zone
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+/// to be updated). The underlying realization of a "transaction" will differ
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+/// for different derived classes; if it uses a general purpose database
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+/// as a backend, it will involve performing some form of "begin transaction"
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+/// statement for the database.
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+///
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+/// Updates (adding or deleting RRs) are made via \c addRRset() and
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+/// \c deleteRRset() methods. Until the \c commit() method is called the
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+/// changes are local to the updater object. For example, they won't be
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+/// visible via a \c ZoneFinder object except the one returned by the
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+/// updater's own \c getFinder() method. The \c commit() completes the
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+/// transaction and makes the changes visible to others.
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+///
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+/// This class does not provide an explicit "rollback" interface. If
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+/// something wrong or unexpected happens during the updates and the
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+/// caller wants to cancel the intermediate updates, the caller should
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+/// simply destruct the updater object without calling \c commit().
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+/// The destructor is supposed to perform the "rollback" operation,
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+/// depending on the internal details of the derived class.
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+///
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+/// \note This initial implementation provides a quite simple interface of
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+/// adding and deleting RRs (see the description of the related methods).
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+/// It may be revisited as we gain more experiences.
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+class ZoneUpdater {
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+protected:
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+ /// The default constructor.
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+ ///
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+ /// This is intentionally defined as protected to ensure that this base
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+ /// class is never instantiated directly.
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+ ZoneUpdater() {}
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+
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+public:
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+ /// The destructor
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+ ///
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+ /// Each derived class implementation must ensure that if \c commit()
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+ /// has not been performed by the time of the call to it, then it
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+ /// "rollbacks" the updates made via the updater so far.
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+ virtual ~ZoneUpdater() {}
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+
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+ /// Return a finder for the zone being updated.
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+ ///
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+ /// The returned finder provides the functionalities of \c ZoneFinder
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+ /// for the zone as updates are made via the updater. That is, before
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+ /// making any update, the finder will be able to find all RRsets that
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+ /// exist in the zone at the time the updater is created. If RRsets
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+ /// are added or deleted via \c addRRset() or \c deleteRRset(),
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+ /// this finder will find the added ones or miss the deleted ones
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+ /// respectively.
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+ ///
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+ /// The finder returned by this method is effective only while the updates
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+ /// are performed, i.e., from the construction of the corresponding
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+ /// updater until \c commit() is performed or the updater is destructed
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+ /// without commit. The result of a subsequent call to this method (or
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+ /// the use of the result) after that is undefined.
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+ ///
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+ /// \return A reference to a \c ZoneFinder for the updated zone
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+ virtual ZoneFinder& getFinder() = 0;
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+
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+ /// Add an RRset to a zone via the updater
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+ ///
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+ /// This may be revisited in a future version, but right now the intended
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+ /// behavior of this method is simple: It "naively" adds the specified
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+ /// RRset to the zone specified on creation of the updater.
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+ /// It performs minimum level of validation on the specified RRset:
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+ /// - Whether the RR class is identical to that for the zone to be updated
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+ /// - Whether the RRset is not empty, i.e., it has at least one RDATA
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+ /// - Whether the RRset is not associated with an RRSIG, i.e.,
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+ /// whether \c getRRsig() on the RRset returns a NULL pointer.
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+ ///
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+ /// and otherwise does not check any oddity. For example, it doesn't
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+ /// check whether the owner name of the specified RRset is a subdomain
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+ /// of the zone's origin; it doesn't care whether or not there is already
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+ /// an RRset of the same name and RR type in the zone, and if there is,
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+ /// whether any of the existing RRs have duplicate RDATA with the added
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+ /// ones. If these conditions matter the calling application must examine
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+ /// the existing data beforehand using the \c ZoneFinder returned by
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+ /// \c getFinder().
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+ ///
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+ /// The validation requirement on the associated RRSIG is temporary.
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+ /// If we find it more reasonable and useful to allow adding a pair of
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+ /// RRset and its RRSIG RRset as we gain experiences with the interface,
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+ /// we may remove this restriction. Until then we explicitly check it
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+ /// to prevent accidental misuse.
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+ ///
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+ /// Conceptually, on successful call to this method, the zone will have
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+ /// the specified RRset, and if there is already an RRset of the same
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+ /// name and RR type, these two sets will be "merged". "Merged" means
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+ /// that a subsequent call to \c ZoneFinder::find() for the name and type
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+ /// will result in success and the returned RRset will contain all
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+ /// previously existing and newly added RDATAs with the TTL being the
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+ /// minimum of the two RRsets. The underlying representation of the
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+ /// "merged" RRsets may vary depending on the characteristic of the
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+ /// underlying data source. For example, if it uses a general purpose
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+ /// database that stores each RR of the same RRset separately, it may
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+ /// simply be a larger sets of RRs based on both the existing and added
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+ /// RRsets; the TTLs of the RRs may be different within the database, and
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+ /// there may even be duplicate RRs in different database rows. As long
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+ /// as the RRset returned via \c ZoneFinder::find() conforms to the
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+ /// concept of "merge", the actual internal representation is up to the
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+ /// implementation.
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+ ///
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+ /// This method must not be called once commit() is performed. If it
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+ /// calls after \c commit() the implementation must throw a
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+ /// \c DataSourceError exception.
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+ ///
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+ /// \todo As noted above we may have to revisit the design details as we
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+ /// gain experiences:
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+ ///
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+ /// - we may want to check (and maybe reject) if there is already a
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+ /// duplicate RR (that has the same RDATA).
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+ /// - we may want to check (and maybe reject) if there is already an
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+ /// RRset of the same name and RR type with different TTL
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+ /// - we may even want to check if there is already any RRset of the
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+ /// same name and RR type.
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+ /// - we may want to add an "options" parameter that can control the
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+ /// above points
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+ /// - we may want to have this method return a value containing the
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+ /// information on whether there's a duplicate, etc.
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+ ///
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+ /// \exception DataSourceError Called after \c commit(), RRset is invalid
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+ /// (see above), internal data source error
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+ /// \exception std::bad_alloc Resource allocation failure
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+ ///
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+ /// \param rrset The RRset to be added
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+ virtual void addRRset(const isc::dns::RRset& rrset) = 0;
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+
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+ /// Delete an RRset from a zone via the updater
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+ ///
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+ /// Like \c addRRset(), the detailed semantics and behavior of this method
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+ /// may have to be revisited in a future version. The following are
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+ /// based on the initial implementation decisions.
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+ ///
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+ /// On successful completion of this method, it will remove from the zone
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+ /// the RRs of the specified owner name and RR type that match one of
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+ /// the RDATAs of the specified RRset. There are several points to be
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+ /// noted:
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+ /// - Existing RRs that don't match any of the specified RDATAs will
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+ /// remain in the zone.
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+ /// - Any RRs of the specified RRset that doesn't exist in the zone will
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+ /// simply be ignored; the implementation of this method is not supposed
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+ /// to check that condition.
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+ /// - The TTL of the RRset is ignored; matching is only performed by
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+ /// the owner name, RR type and RDATA
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+ ///
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+ /// Ignoring the TTL may not look sensible, but it's based on the
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+ /// observation that it will result in more intuitive result, especially
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+ /// when the underlying data source is a general purpose database.
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+ /// See also \c DatabaseAccessor::deleteRecordInZone() on this point.
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+ /// It also matches the dynamic update protocol (RFC2136), where TTLs
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+ /// are ignored when deleting RRs.
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+ ///
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+ /// \note Since the TTL is ignored, this method could take the RRset
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+ /// to be deleted as a tuple of name, RR type, and a list of RDATAs.
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+ /// But in practice, it's quite likely that the caller has the RRset
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+ /// in the form of the \c RRset object (e.g., extracted from a dynamic
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+ /// update request message), so this interface would rather be more
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+ /// convenient. If it turns out not to be true we can change or extend
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+ /// the method signature.
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+ ///
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+ /// This method performs minimum level of validation on the specified
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+ /// RRset:
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+ /// - Whether the RR class is identical to that for the zone to be updated
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+ /// - Whether the RRset is not empty, i.e., it has at least one RDATA
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+ /// - Whether the RRset is not associated with an RRSIG, i.e.,
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+ /// whether \c getRRsig() on the RRset returns a NULL pointer.
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+ ///
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+ /// This method must not be called once commit() is performed. If it
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+ /// calls after \c commit() the implementation must throw a
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+ /// \c DataSourceError exception.
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+ ///
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+ /// \todo As noted above we may have to revisit the design details as we
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+ /// gain experiences:
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+ ///
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+ /// - we may want to check (and maybe reject) if some or all of the RRs
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+ /// for the specified RRset don't exist in the zone
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+ /// - we may want to allow an option to "delete everything" for specified
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+ /// name and/or specified name + RR type.
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+ /// - as mentioned above, we may want to include the TTL in matching the
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+ /// deleted RRs
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+ /// - we may want to add an "options" parameter that can control the
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+ /// above points
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+ /// - we may want to have this method return a value containing the
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+ /// information on whether there's any RRs that are specified but don't
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+ /// exit, the number of actually deleted RRs, etc.
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+ ///
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+ /// \exception DataSourceError Called after \c commit(), RRset is invalid
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+ /// (see above), internal data source error
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+ /// \exception std::bad_alloc Resource allocation failure
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+ ///
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+ /// \param rrset The RRset to be deleted
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+ virtual void deleteRRset(const isc::dns::RRset& rrset) = 0;
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+
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+ /// Commit the updates made in the updater to the zone
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+ ///
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+ /// This method completes the "transaction" started at the creation
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+ /// of the updater. After successful completion of this method, the
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+ /// updates will be visible outside the scope of the updater.
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+ /// The actual internal behavior will defer for different derived classes.
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+ /// For a derived class with a general purpose database as a backend,
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+ /// for example, this method would perform a "commit" statement for the
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+ /// database.
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+ ///
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+ /// This operation can only be performed at most once. A duplicate call
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+ /// must result in a DatasourceError exception.
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+ ///
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+ /// \exception DataSourceError Duplicate call of the method,
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+ /// internal data source error
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+ virtual void commit() = 0;
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+};
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+
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+/// \brief A pointer-like type pointing to a \c ZoneUpdater object.
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+typedef boost::shared_ptr<ZoneUpdater> ZoneUpdaterPtr;
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+
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+} // end of datasrc
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+} // end of isc
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#endif // __ZONE_H
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JINMEI Tatuya