fostore20/src/java/org/apache/jdo/impl/fostore/OID.java - db-jdo - Git at Google

 /*
  * Copyright 2005 The Apache Software Foundation.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package org.apache.jdo.impl.fostore;

 import java.io.DataInput;
 import java.io.DataOutput;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.Serializable;

 import java.util.StringTokenizer;

 import javax.jdo.JDOFatalException;
 import javax.jdo.JDOUserException;
 import javax.jdo.spi.PersistenceCapable;

 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;

 import org.apache.jdo.state.StateManagerInternal;
 import org.apache.jdo.util.I18NHelper;
 import org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeFactory;
 import org.netbeans.mdr.persistence.Storage;
 import org.netbeans.mdr.persistence.MOFID;

 /**
  * Represents the identity of a JDO object in the File/Object store.  This
  * implementation uses datastore identity.  The identity is based on the class
  * of the object and a unique identifier within that class.  These OID's are
  * unique only within a single datastore.
  * <p>
  * This class is <code>public</code> as required by the JDO specification.
  *
  * @author Dave Bristor
  * @version 1.0.1
  */
 // XXX TBD Remote: Allocate provisional OID's per-PMF w/ remote store.
 public class OID implements Serializable, Comparable {
     //
     // Make sure that the number of bits uses here add up to the right number
     // of bits as per the size of the OID.
     //
     // In the initial implementation, we are using a long as the size of the
     // OID.  The layout is:
     // [reserved: 2] [provisional-CLID: 1] [provisional-UID: 1] [class id: 12] [unique id: 48]
     //
     static final long RESERVED_MASK =    0xc000000000000000L;
     static final long PROV_UID_MASK =    0x1000000000000000L;
     static final long PROV_CLID_MASK =   0x2000000000000000L;
     static final long CLID_MASK =        0x0fff000000000000L;
     static final long UID_MASK =         0x0000ffffffffffffL;

     // Shift a clid's id by this much to "or" it into an oid.
     static final int CLID_SHIFT = 48;

     // Maximum value for a CLID and UID.
     static final int MAX_CLID = (int)(CLID_MASK >> CLID_SHIFT);
     static final long MAX_UID = UID_MASK;

     // Shift the reserved bits over by this much to "or" them into an oid.
     static final int RESERVED_SHIFT = 61;

     /**
     * The 'value' of this OID.
     */
     // JDO spec - required.
     public long oid;

     // Hashcode uniquely identifying this CLID within this JVM.
     private int hashCode;

     // The value for oid that will be used by the next-created provisional OID.
     private static long nextProvisional = 0;

     // The Class that defined this OID
     private Class pcClass = null;

     // For synchronizing access to nextProvisional;
     private static final Integer lock = new Integer(1);

     /** I18N support. */
     static final I18NHelper msg = I18NHelper.getInstance(I18N.NAME);

     /** Logger */
     static final Log logger = LogFactory.getFactory().getInstance(
         "org.apache.jdo.impl.fostore"); // NOI18N

     //
     // OID's are created 3 ways:
     // * Creating an "empty" Oid and then (presumably) setting
     //   the long oid value.
     // * Creating a filled-in OID from a long value.
     // * Creting an OID from a CLID.
     //

     /**
     * Creates an OID with the no value.
     */
     // JDO spec - required.
     public OID() { }

     /**
      * Constructor that takes the result of toString() and creates a new
      * OID.  Currently only the CLID and UID are used.  The provisional
      * bits are ignored.
      * @see org.apache.jdo.impl.fostore.OID#toString
      */
     // JDO spec - required.
     public OID (String str) {
         StringTokenizer st = new StringTokenizer (str, "OID: -()"); // NOI18N
         String clid = st.nextToken();
         String uid = st.nextToken();
         long clidBits = Long.parseLong (clid);
         long uidBits = Long.parseLong (uid);
         oid = (clidBits << CLID_SHIFT) | uidBits;
     }

     /**
     * Creates an OID with the given value.
     */
     // public for user convenience
     public OID(long oid) {
         this.oid = oid;
     }

     // Returns a new OID for the given CLID.  The OID is provisional if the
     // CLID is provisional.
     private OID(CLID clid) {
         synchronized(lock) {
             long clidBits = clid.getId();
             clidBits <<= CLID_SHIFT;
             oid = clidBits | ++nextProvisional;

             if (clid.isProvisional()) {
                 oid |= (PROV_UID_MASK | PROV_CLID_MASK);
             }
         }
     }

     //
     // I prefer to avoid using constructors outside of a given class, and to
     // instead use factory methods.  The above constructors which are public
     // are that way for the sake of the JDO spec.  Code within fostore uses
     // these factory methods instead.
     //

     /**
     * Create and return a provisional OID
     * @return A Provisional OID.
     */
     static OID create(CLID clid) {
         OID rc = new OID(clid);
         if (clid.isProvisional()) {
             rc.oid |= PROV_CLID_MASK;
         }
         rc.oid |= PROV_UID_MASK;
         return rc;
     }

     /**
     * Create and return a based on a given representation.
     * @return A real, non-provisional OID.
     * @exception JDOFatalException Thrown if given oid has its provisional bit set.
     */
     OID create(long oid) {
         OID rc = new OID(oid);
         if (rc.isProvisional()) {
             throw new FOStoreFatalInternalException(
                 this.getClass(), "create(oid)", // NOI18N
                 msg.msg("ERR_InvalidAttemptToCreateOID", new Long(oid))); // NOI18N
         }
         return rc;
     }

     /**
     * Provides an OID for the given CLID and UID.  The given CLID must not be
     * provisional, or a JDOFatalException will result.
     * @param clid CLID for the OID.
     * @param uid UID part of the OID.
     * @return A new OID based on the given clid and uid.
     * @exception JDOFatalException Thrown if given CLID is provisional.
     */
     static OID create(CLID clid, long uid) {
         if (clid.isProvisional()) {
             throw new FOStoreFatalInternalException(
                 OID.class, "create(clid, oid)", // NOI18N
                 msg.msg("ERR_InvalidAttemptToCreateOID", clid, new Long(uid))); // NOI18N
         }
         long clidBits = clid.getId();
         clidBits = clidBits << CLID_SHIFT;
         return new OID(clidBits | uid);
     }

     //
     // Provide access to information about an OID.
     //

     /**
     * Indicates whether this OID is provisional.
     * @return true if this OID is provisional, false otherwise.
     */
     public boolean isProvisional() {
         boolean rc = false;
         // If CLID is provisional, it *must* be provisional.  If not, it can
         // still be a real CLID with a provisional UID part.
         if ((oid & PROV_CLID_MASK) != 0) {
             rc = true;
         } else if ((oid & PROV_UID_MASK) != 0) {
             rc = true;
         }
         return rc;
     }

     /**
     * Provides the CLID part of this OID.  The resulting CLID is
     * provisional if it is provisional within this OID.  I.e., this might be a
     * provisional OID, but the CLID part could still be datastore-assigned.
     * @return The CLID part of this OID.
     */
     public CLID getCLID() {
         long clidBits = oid & CLID_MASK;
         clidBits >>= CLID_SHIFT;
         return CLID.create((int)clidBits, (oid & PROV_CLID_MASK) != 0);
     }

     /**
     * Provides the unique id part of this OID.
     * @return The unique id part of this OID.
     */
     public long getUID() {
         return oid & UID_MASK;
     }

     /**
     * Provides a JVM-unique hashCode for this OID.
     */
     public int hashCode() {
         if (0 == hashCode) {
             hashCode = new Long(oid).hashCode();
         }
         return hashCode;
     }

     /**
     * Determines if this OID is equal to another.
     * @param other The other OID in the equality comparison.
     * @return True if they are equal, false otherwise.
     */
     public boolean equals(Object other) {
         boolean rc = false;
         if (other instanceof OID) {
             rc = oid == ((OID)other).oid;
         }
         return rc;
     }

     /**
     * Returns a String representation of this OID.  Includes whether or not
     * the OID is provisional, and its reserved bits, if they are set.
     */
     public String toString() {
         StringBuffer rc =
             new StringBuffer(
                 "OID: " + // NOI18N
                 ((oid & CLID_MASK) >> CLID_SHIFT) +
                 "-" + (oid & UID_MASK)); // NOI18N
         if (isProvisional()) {
             rc.append(" (provisional)"); // NOI18N
         }
         long res = oid & RESERVED_MASK;
         if (res > 0) {
             res = res >> RESERVED_SHIFT;
             rc.append(" (reserved=" + res + ")"); // NOI18N
         }
         return rc.toString();
     }

     /**
     * Returns the id itself in String form, for debugging.
     */
     public String oidString() {
         return "" + oid; // NOI18N
     }

     //
     // Serialization
     // We provide the {write,read}Object methods for java.io.Serialization, so
     // that we know exactly what's being written and read.  We also have
     // methods used elsewhere in the fostore package that don't rely
     // ObjectOutput stuff.
     //

     /**
     * Writes this OID to the output stream.
     */
     private void writeObject(ObjectOutputStream out) throws IOException {
         write(out);
     }

     /**
     * Reads this OID's value from the input stream.
     */
     private void readObject(ObjectInputStream in) throws IOException {
         boolean appIdType = in.readBoolean();
         oid = in.readLong();
     }

     void write(DataOutput out) throws IOException {
         if (logger.isDebugEnabled()) {
             logger.debug("OID.write: " + oid);  // NOI18N
         }
         out.writeBoolean(false);
         out.writeLong(oid);
     }

     static OID read(DataInput in) throws IOException {
         boolean appIdType = in.readBoolean();
         long oid = in.readLong();
         if (logger.isDebugEnabled()) {
             logger.debug("OID.read: " + oid + " appIdType: " + appIdType);  // NOI18N
         }
         OID rc = null;
         if (appIdType) {
             rc = new AID(oid);
             ((AID)rc).readBuffer(in);
         } else {
             rc = new OID(oid);
         }
         return rc;
     }

     /**
      * Skip OID bytes from the input.
      * @param in DataInput.
      * @throws IOException.
      */
     static void skip(DataInput in) throws IOException {
         boolean appIdType = in.readBoolean();
         long oid = in.readLong();
         if (logger.isDebugEnabled()) {
             logger.debug("OID.skip: " + oid + " appIdType: " + appIdType);  // NOI18N
         }
         if (appIdType) {
             int length = in.readInt();
             in.skipBytes(length);
         }
     }

     //
     // Implementation methods.
     //

     /**
      * Returns copy of the requested oid to be accessed by the user.
      */
     Object getExternalObjectId(PersistenceCapable pc) {
         return new OID(oid);
     }

     /**
     * Provides the OID in a form that can be used by the database as a key.
     */
     MOFID keyValue(FOStoreBtreeStorage storage) {
         return storage.createMOFID(getCLID().getId(), getUID());
     }

     /** Replaces provisional oid with real oid (datastore identity only)
      * @param realOID as OID instance
      * @param pmf as FOStorePMF
      * @param sm as StateManagerInternal
      */
     void replaceProvisionalOIDWithReal(OID realOID, FOStorePMF pmf,
         StateManagerInternal sm) {

         pmf.mapProvisionalOIDToReal(this, realOID);
         sm.setObjectId(realOID);
     }

     /**
      * Returns copy of the requested oid.
      */
     OID copy() {
         return new OID(oid);
     }

     /**
      * Copy key fields from OID into PC instance. No-op for the
      * datastore identity type for this OID.
      * @param sm as StateManagerInternal
      * @param pmf as FOStorePMF
      * @param pcClass Class of the PC instance.
      * @param pkfields array of PK field numbers.
      */
     void copyKeyFieldsToPC(StateManagerInternal sm, FOStorePMF pmf,
                                     Class pcClass, int[] pkfields) {}

     /**
      * Returns Class that defined OID.
      * @param pmf as FOStorePMF
      */
     Class getPCClass(FOStorePMF pmf) {
         if (pcClass == null) {
             FOStoreModel model = pmf.getModel();
             pcClass = model.getClass(getCLID());
             if (logger.isDebugEnabled()) {
                 logger.debug("OID.getPCClass: " + getCLID() + " " + pcClass);  // NOI18N
             }
         }
         return pcClass;
     }

     /**
      * Returns false for application identity type for this OID.
      */
     boolean isApplicationIdentity() {
         return false;
     }

     /**
      * Returns true for datastore identity type for this OID.
      */
     boolean isDataStoreIdentity() {
         return true;
     }

     /** Compare this OID to another OID. This is needed to implement an
      * absolute ordering of OIDs. The ordering must provide for comparing
      * provisional OIDs to permanent OIDs, with all provisional OIDs
      * comparing greater than all permanent OIDs.
      * @since 1.0.1
      */
     public int compareTo(Object obj) {
         if (!(obj instanceof OID)) {
             throw new JDOUserException(msg.msg("EXC_CannotCompareNonOID")); // NOI18N
         }
         OID other = (OID)obj;
         // if other is provisional and we're not, other is bigger
         if (other.isProvisional() & !this.isProvisional()) {
             return -1;
         } else if (this.isProvisional() & !other.isProvisional()) {
             return 1;
         } else // compare UIDs
             // both are provisional or both not; which is bigger UID?
             return (this.getUID() < other.getUID())?-1:1;
     }

 }
	/*
	* Copyright 2005 The Apache Software Foundation.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package org.apache.jdo.impl.fostore;

	import java.io.DataInput;
	import java.io.DataOutput;
	import java.io.IOException;
	import java.io.ObjectInputStream;
	import java.io.ObjectOutputStream;
	import java.io.Serializable;

	import java.util.StringTokenizer;

	import javax.jdo.JDOFatalException;
	import javax.jdo.JDOUserException;
	import javax.jdo.spi.PersistenceCapable;

	import org.apache.commons.logging.Log;
	import org.apache.commons.logging.LogFactory;

	import org.apache.jdo.state.StateManagerInternal;
	import org.apache.jdo.util.I18NHelper;
	import org.netbeans.mdr.persistence.btreeimpl.btreestorage.BtreeFactory;
	import org.netbeans.mdr.persistence.Storage;
	import org.netbeans.mdr.persistence.MOFID;

	/**
	* Represents the identity of a JDO object in the File/Object store. This
	* implementation uses datastore identity. The identity is based on the class
	* of the object and a unique identifier within that class. These OID's are
	* unique only within a single datastore.
	* <p>
	* This class is <code>public</code> as required by the JDO specification.
	*
	* @author Dave Bristor
	* @version 1.0.1
	*/
	// XXX TBD Remote: Allocate provisional OID's per-PMF w/ remote store.
	public class OID implements Serializable, Comparable {
	//
	// Make sure that the number of bits uses here add up to the right number
	// of bits as per the size of the OID.
	//
	// In the initial implementation, we are using a long as the size of the
	// OID. The layout is:
	// [reserved: 2] [provisional-CLID: 1] [provisional-UID: 1] [class id: 12] [unique id: 48]
	//
	static final long RESERVED_MASK = 0xc000000000000000L;
	static final long PROV_UID_MASK = 0x1000000000000000L;
	static final long PROV_CLID_MASK = 0x2000000000000000L;
	static final long CLID_MASK = 0x0fff000000000000L;
	static final long UID_MASK = 0x0000ffffffffffffL;

	// Shift a clid's id by this much to "or" it into an oid.
	static final int CLID_SHIFT = 48;

	// Maximum value for a CLID and UID.
	static final int MAX_CLID = (int)(CLID_MASK >> CLID_SHIFT);
	static final long MAX_UID = UID_MASK;

	// Shift the reserved bits over by this much to "or" them into an oid.
	static final int RESERVED_SHIFT = 61;

	/**
	* The 'value' of this OID.
	*/
	// JDO spec - required.
	public long oid;

	// Hashcode uniquely identifying this CLID within this JVM.
	private int hashCode;

	// The value for oid that will be used by the next-created provisional OID.
	private static long nextProvisional = 0;

	// The Class that defined this OID
	private Class pcClass = null;

	// For synchronizing access to nextProvisional;
	private static final Integer lock = new Integer(1);

	/** I18N support. */
	static final I18NHelper msg = I18NHelper.getInstance(I18N.NAME);

	/** Logger */
	static final Log logger = LogFactory.getFactory().getInstance(
	"org.apache.jdo.impl.fostore"); // NOI18N

	//
	// OID's are created 3 ways:
	// * Creating an "empty" Oid and then (presumably) setting
	// the long oid value.
	// * Creating a filled-in OID from a long value.
	// * Creting an OID from a CLID.
	//

	/**
	* Creates an OID with the no value.
	*/
	// JDO spec - required.
	public OID() { }

	/**
	* Constructor that takes the result of toString() and creates a new
	* OID. Currently only the CLID and UID are used. The provisional
	* bits are ignored.
	* @see org.apache.jdo.impl.fostore.OID#toString
	*/
	// JDO spec - required.
	public OID (String str) {
	StringTokenizer st = new StringTokenizer (str, "OID: -()"); // NOI18N
	String clid = st.nextToken();
	String uid = st.nextToken();
	long clidBits = Long.parseLong (clid);
	long uidBits = Long.parseLong (uid);
	oid = (clidBits << CLID_SHIFT) \| uidBits;
	}

	/**
	* Creates an OID with the given value.
	*/
	// public for user convenience
	public OID(long oid) {
	this.oid = oid;
	}

	// Returns a new OID for the given CLID. The OID is provisional if the
	// CLID is provisional.
	private OID(CLID clid) {
	synchronized(lock) {
	long clidBits = clid.getId();
	clidBits <<= CLID_SHIFT;
	oid = clidBits \| ++nextProvisional;

	if (clid.isProvisional()) {
	oid \|= (PROV_UID_MASK \| PROV_CLID_MASK);
	}
	}
	}

	//
	// I prefer to avoid using constructors outside of a given class, and to
	// instead use factory methods. The above constructors which are public
	// are that way for the sake of the JDO spec. Code within fostore uses
	// these factory methods instead.
	//

	/**
	* Create and return a provisional OID
	* @return A Provisional OID.
	*/
	static OID create(CLID clid) {
	OID rc = new OID(clid);
	if (clid.isProvisional()) {
	rc.oid \|= PROV_CLID_MASK;
	}
	rc.oid \|= PROV_UID_MASK;
	return rc;
	}

	/**
	* Create and return a based on a given representation.
	* @return A real, non-provisional OID.
	* @exception JDOFatalException Thrown if given oid has its provisional bit set.
	*/
	OID create(long oid) {
	OID rc = new OID(oid);
	if (rc.isProvisional()) {
	throw new FOStoreFatalInternalException(
	this.getClass(), "create(oid)", // NOI18N
	msg.msg("ERR_InvalidAttemptToCreateOID", new Long(oid))); // NOI18N
	}
	return rc;
	}

	/**
	* Provides an OID for the given CLID and UID. The given CLID must not be
	* provisional, or a JDOFatalException will result.
	* @param clid CLID for the OID.
	* @param uid UID part of the OID.
	* @return A new OID based on the given clid and uid.
	* @exception JDOFatalException Thrown if given CLID is provisional.
	*/
	static OID create(CLID clid, long uid) {
	if (clid.isProvisional()) {
	throw new FOStoreFatalInternalException(
	OID.class, "create(clid, oid)", // NOI18N
	msg.msg("ERR_InvalidAttemptToCreateOID", clid, new Long(uid))); // NOI18N
	}
	long clidBits = clid.getId();
	clidBits = clidBits << CLID_SHIFT;
	return new OID(clidBits \| uid);
	}

	//
	// Provide access to information about an OID.
	//

	/**
	* Indicates whether this OID is provisional.
	* @return true if this OID is provisional, false otherwise.
	*/
	public boolean isProvisional() {
	boolean rc = false;
	// If CLID is provisional, it must be provisional. If not, it can
	// still be a real CLID with a provisional UID part.
	if ((oid & PROV_CLID_MASK) != 0) {
	rc = true;
	} else if ((oid & PROV_UID_MASK) != 0) {
	rc = true;
	}
	return rc;
	}

	/**
	* Provides the CLID part of this OID. The resulting CLID is
	* provisional if it is provisional within this OID. I.e., this might be a
	* provisional OID, but the CLID part could still be datastore-assigned.
	* @return The CLID part of this OID.
	*/
	public CLID getCLID() {
	long clidBits = oid & CLID_MASK;
	clidBits >>= CLID_SHIFT;
	return CLID.create((int)clidBits, (oid & PROV_CLID_MASK) != 0);
	}

	/**
	* Provides the unique id part of this OID.
	* @return The unique id part of this OID.
	*/
	public long getUID() {
	return oid & UID_MASK;
	}

	/**
	* Provides a JVM-unique hashCode for this OID.
	*/
	public int hashCode() {
	if (0 == hashCode) {
	hashCode = new Long(oid).hashCode();
	}
	return hashCode;
	}

	/**
	* Determines if this OID is equal to another.
	* @param other The other OID in the equality comparison.
	* @return True if they are equal, false otherwise.
	*/
	public boolean equals(Object other) {
	boolean rc = false;
	if (other instanceof OID) {
	rc = oid == ((OID)other).oid;
	}
	return rc;
	}

	/**
	* Returns a String representation of this OID. Includes whether or not
	* the OID is provisional, and its reserved bits, if they are set.
	*/
	public String toString() {
	StringBuffer rc =
	new StringBuffer(
	"OID: " + // NOI18N
	((oid & CLID_MASK) >> CLID_SHIFT) +
	"-" + (oid & UID_MASK)); // NOI18N
	if (isProvisional()) {
	rc.append(" (provisional)"); // NOI18N
	}
	long res = oid & RESERVED_MASK;
	if (res > 0) {
	res = res >> RESERVED_SHIFT;
	rc.append(" (reserved=" + res + ")"); // NOI18N
	}
	return rc.toString();
	}

	/**
	* Returns the id itself in String form, for debugging.
	*/
	public String oidString() {
	return "" + oid; // NOI18N
	}

	//
	// Serialization
	// We provide the {write,read}Object methods for java.io.Serialization, so
	// that we know exactly what's being written and read. We also have
	// methods used elsewhere in the fostore package that don't rely
	// ObjectOutput stuff.
	//

	/**
	* Writes this OID to the output stream.
	*/
	private void writeObject(ObjectOutputStream out) throws IOException {
	write(out);
	}

	/**
	* Reads this OID's value from the input stream.
	*/
	private void readObject(ObjectInputStream in) throws IOException {
	boolean appIdType = in.readBoolean();
	oid = in.readLong();
	}

	void write(DataOutput out) throws IOException {
	if (logger.isDebugEnabled()) {
	logger.debug("OID.write: " + oid); // NOI18N
	}
	out.writeBoolean(false);
	out.writeLong(oid);
	}

	static OID read(DataInput in) throws IOException {
	boolean appIdType = in.readBoolean();
	long oid = in.readLong();
	if (logger.isDebugEnabled()) {
	logger.debug("OID.read: " + oid + " appIdType: " + appIdType); // NOI18N
	}
	OID rc = null;
	if (appIdType) {
	rc = new AID(oid);
	((AID)rc).readBuffer(in);
	} else {
	rc = new OID(oid);
	}
	return rc;
	}

	/**
	* Skip OID bytes from the input.
	* @param in DataInput.
	* @throws IOException.
	*/
	static void skip(DataInput in) throws IOException {
	boolean appIdType = in.readBoolean();
	long oid = in.readLong();
	if (logger.isDebugEnabled()) {
	logger.debug("OID.skip: " + oid + " appIdType: " + appIdType); // NOI18N
	}
	if (appIdType) {
	int length = in.readInt();
	in.skipBytes(length);
	}
	}

	//
	// Implementation methods.
	//

	/**
	* Returns copy of the requested oid to be accessed by the user.
	*/
	Object getExternalObjectId(PersistenceCapable pc) {
	return new OID(oid);
	}

	/**
	* Provides the OID in a form that can be used by the database as a key.
	*/
	MOFID keyValue(FOStoreBtreeStorage storage) {
	return storage.createMOFID(getCLID().getId(), getUID());
	}

	/** Replaces provisional oid with real oid (datastore identity only)
	* @param realOID as OID instance
	* @param pmf as FOStorePMF
	* @param sm as StateManagerInternal
	*/
	void replaceProvisionalOIDWithReal(OID realOID, FOStorePMF pmf,
	StateManagerInternal sm) {

	pmf.mapProvisionalOIDToReal(this, realOID);
	sm.setObjectId(realOID);
	}

	/**
	* Returns copy of the requested oid.
	*/
	OID copy() {
	return new OID(oid);
	}

	/**
	* Copy key fields from OID into PC instance. No-op for the
	* datastore identity type for this OID.
	* @param sm as StateManagerInternal
	* @param pmf as FOStorePMF
	* @param pcClass Class of the PC instance.
	* @param pkfields array of PK field numbers.
	*/
	void copyKeyFieldsToPC(StateManagerInternal sm, FOStorePMF pmf,
	Class pcClass, int[] pkfields) {}

	/**
	* Returns Class that defined OID.
	* @param pmf as FOStorePMF
	*/
	Class getPCClass(FOStorePMF pmf) {
	if (pcClass == null) {
	FOStoreModel model = pmf.getModel();
	pcClass = model.getClass(getCLID());
	if (logger.isDebugEnabled()) {
	logger.debug("OID.getPCClass: " + getCLID() + " " + pcClass); // NOI18N
	}
	}
	return pcClass;
	}

	/**
	* Returns false for application identity type for this OID.
	*/
	boolean isApplicationIdentity() {
	return false;
	}

	/**
	* Returns true for datastore identity type for this OID.
	*/
	boolean isDataStoreIdentity() {
	return true;
	}

	/** Compare this OID to another OID. This is needed to implement an
	* absolute ordering of OIDs. The ordering must provide for comparing
	* provisional OIDs to permanent OIDs, with all provisional OIDs
	* comparing greater than all permanent OIDs.
	* @since 1.0.1
	*/
	public int compareTo(Object obj) {
	if (!(obj instanceof OID)) {
	throw new JDOUserException(msg.msg("EXC_CannotCompareNonOID")); // NOI18N
	}
	OID other = (OID)obj;
	// if other is provisional and we're not, other is bigger
	if (other.isProvisional() & !this.isProvisional()) {
	return -1;
	} else if (this.isProvisional() & !other.isProvisional()) {
	return 1;
	} else // compare UIDs
	// both are provisional or both not; which is bigger UID?
	return (this.getUID() < other.getUID())?-1:1;
	}

	}