Offer_Database.h

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// -*- C++ -*-

//=============================================================================
/**
 *  @file    Offer_Database.h
 *
 *  $Id: Offer_Database.h 77001 2007-02-12 07:54:49Z johnnyw $
 *
 *  @author Seth Widoff <sbw1@cs.wustl.edu>
 */
//=============================================================================


#ifndef TAO_OFFER_DATABASE_H
#define TAO_OFFER_DATABASE_H
#include /**/ "ace/pre.h"

#include "orbsvcs/Trader/Trader.h"
#include "orbsvcs/Trader/Offer_Iterators.h"
#include "ace/Null_Mutex.h"

TAO_BEGIN_VERSIONED_NAMESPACE_DECL

template <class LOCK_TYPE> class TAO_Service_Offer_Iterator;

/**
 * @class TAO_Offer_Database
 *
 * The TAO_Offer_Database encapsulates the mapping of service
 * types to those offers exported with that service types. The
 * underlying structure is a map of maps. The first maps maps the
 * service type name to a map of exported offers. The second map
 * maps the identifying index for that offer within the service
 * types. So a service type name and an index uniquely identifies an
 * exported offer. In fact, when the register export interface
 * returns a CosTrading::OfferId, it's returning no more than a
 * simple string concatenation of these two values. In addition to
 * all these wonderful things, the TAO_Offer_Database has built-in
 * locking, one reader/writer-style lock for modifying the top-level
 * map and a reader/writer-style for each of the offer
 * maps. Needless to say the locks are acquired when the
 * TAO_Offer_Database performs operations on the structures they
 * guard.
 * NOTE: TAO_Offer_Database needs to be parameterized by a
 * READER/WRITER LOCK, a RECURSIVE MUTEX, or a NULL MUTEX, not a
 * simple binary mutex! Mutexes will cause deadlock when you try to
 * contruct an iterator (which acquires a read lock on the map under
 * an existing read lock). Just don't do it, ok?
 */
template <class LOCK_TYPE>
class TAO_Offer_Database
{
  friend class TAO_Service_Offer_Iterator<LOCK_TYPE>;
public:

  // Traits
  typedef TAO_Service_Offer_Iterator<LOCK_TYPE> offer_iterator;

  /// No arg constructor.
  TAO_Offer_Database (void);

  ~TAO_Offer_Database (void);

  /// Add an offer of type <type> and generate a CosTrading::OfferId
  /// for it. Returns 0 on failure.
  CosTrading::OfferId insert_offer (const char* type,
                                    CosTrading::Offer* offer);

  int remove_offer (const CosTrading::OfferId offer_id);

  /// Lookup an offer whose offer_id is <offer_id>, and return
  /// it. Otherwise, throw the appropriate exception.
  CosTrading::Offer* lookup_offer (const CosTrading::OfferId offer_id);

  /**
   * Lookup an offer whose OfferId is <offer_id> and return in
   * <type_name> the type name of the object. Type name is just a
   * pointer to a location in offer_id, so DON'T DELETE IT.
   */
  CosTrading::Offer* lookup_offer (const CosTrading::OfferId offer_id,
                                   char*& type_name);

  /// Return an iterator that will traverse and return all the offer
  /// ids in the service type map.
  TAO_Offer_Id_Iterator* retrieve_all_offer_ids (void);

  struct Offer_Map_Entry
  {
    TAO_Offer_Map* offer_map_;
    CORBA::ULong counter_;
    LOCK_TYPE lock_;
  };

  typedef ACE_Hash_Map_Manager_Ex
    <
    CORBA::String_var,
    Offer_Map_Entry*,
    ACE_Hash<CORBA::String_var>,
    ACE_Equal_To<CORBA::String_var>,
    ACE_Null_Mutex
    >
    Offer_Database;

private:

  // The internal id is a pointer here, not only to avoid copying,
  // since we would only copy on insertion, and we only insert once
  // --- with an empty Offer_Map_Entry --- but also since most locks
  // have unimplemented copy constructors.

  /// Lookup an offer whose type is <type> and id, <id>. Return 0 on
  /// failure.
  CosTrading::Offer* lookup_offer (const char* type,
                                   CORBA::ULong id);

  /**
   * Remove an offers whose id is <offer_id>. Returns 0 on success, -1
   * on failure, and throws a CosTrading::IllegalOfferId if it can't
   * parse the CosTrading::OfferId.
   */
  int remove_offer (const char* type, CORBA::ULong id);

  /// Take in a service type name for the offer the current value of
  /// of the counter and generate an offer id.
  static CosTrading::OfferId generate_offer_id (const char *type_name,
                                                CORBA::ULong id);

  /// Take in a previously generated offer id and return the type
  /// and id that were used to generate the offer id.
  static void parse_offer_id (const CosTrading::OfferId offer_id,
                              char* &service_type,
                              CORBA::ULong& id);

  // = Disallow these operations.
  ACE_UNIMPLEMENTED_FUNC (void operator= (const TAO_Offer_Database<LOCK_TYPE> &))
  ACE_UNIMPLEMENTED_FUNC (TAO_Offer_Database (const TAO_Offer_Database<LOCK_TYPE> &))

  LOCK_TYPE db_lock_;

  Offer_Database offer_db_;
  // The protected data structure.
};

/**
 * @class TAO_Service_Offer_Iterator
 *
 * @brief TAO_Service_Offer_Iterator iterates over the set of exported
 * offers for a given type. Handily, it takes care of all the
 * necessary locking, acquiring them in the constructor, and
 * releasing them in the destructor.
 */
template <class LOCK_TYPE>
class TAO_Service_Offer_Iterator
{
 public:

  typedef TAO_Offer_Database<LOCK_TYPE> Offer_Database;

  TAO_Service_Offer_Iterator (const char* type,
                              TAO_Offer_Database<LOCK_TYPE>& offer_database);

  /// Release all the locks acquired.
  ~TAO_Service_Offer_Iterator (void);

  /// Returns 1 if there are more offers, 0 otherwise.
  int has_more_offers (void);

  /// Get the id for the current offer.
  CosTrading::OfferId get_id (void);

  /// Returns the next offer in the series.
  CosTrading::Offer* get_offer (void);

  /// Advances the iterator 1.
  void next_offer (void);

 private:
  // Protected constructor.

  /// Lock the top_level map.
  TAO_Offer_Database<LOCK_TYPE>& stm_;

  /// Lock for the internal map.
  LOCK_TYPE* lock_;

  /// Iterator over the actual offer map.
  TAO_Offer_Map::iterator* offer_iter_;

  /// The name of the type. Used for constructing offer ids.
  const char* type_;
};

TAO_END_VERSIONED_NAMESPACE_DECL

#if defined (ACE_TEMPLATES_REQUIRE_SOURCE)
#include "orbsvcs/Trader/Offer_Database.cpp"
#endif  /* ACE_TEMPLATES_REQUIRE_SOURCE */

#include /**/ "ace/post.h"
#endif /* TAO_SERVICE_TYPE_MAP_H */

---