/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2010-2014, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.engine.spi;

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

import org.hibernate.AssertionFailure;
import org.hibernate.CustomEntityDirtinessStrategy;
import org.hibernate.EntityMode;
import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.Session;
import org.hibernate.bytecode.instrumentation.spi.FieldInterceptor;
import org.hibernate.engine.internal.EntityEntryExtraStateHolder;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.persister.entity.UniqueKeyLoadable;
import org.hibernate.pretty.MessageHelper;

We need an entry to tell us all about the current state of an object with respect to its persistent state
Implementation Warning: Hibernate needs to instantiate a high amount of instances of this class,
therefore we need to take care of its impact on memory consumption.
Author:
Gavin King, Emmanuel Bernard , Gunnar Morling, Sanne Grinovero  /**
 * We need an entry to tell us all about the current state of an object with respect to its persistent state
 *
 * Implementation Warning: Hibernate needs to instantiate a high amount of instances of this class,
 * therefore we need to take care of its impact on memory consumption.
 *
 * @author Gavin King
 * @author Emmanuel Bernard <emmanuel@hibernate.org>
 * @author Gunnar Morling
 * @author Sanne Grinovero  <sanne@hibernate.org>
 */
public final class EntityEntry implements Serializable {
	private final Serializable id;
	private Object[] loadedState;
	private Object version;
	private final EntityPersister persister; // permanent but we only need the entityName state in a non transient way
	private transient EntityKey cachedEntityKey; // cached EntityKey (lazy-initialized)
	private final transient Object rowId;
	private final transient PersistenceContext persistenceContext;
	private EntityEntryExtraState next;

	
Holds several boolean and enum typed attributes in a very compact manner. Enum values are stored in 4 bits (where 0 represents null, and each enum value is represented by its ordinal value + 1), thus allowing for up to 15 values per enum. Boolean values are stored in one bit. 

The value is structured as follows:
1 - Lock mode
2 - Status
3 - Previous Status
4 - existsInDatabase
5 - isBeingReplicated
6 - loadedWithLazyPropertiesUnfetched; NOTE: this is not updated when properties are fetched lazily!
0000 0000 | 0000 0000 | 0654 3333 | 2222 1111
 Use setCompressedValue(EnumState<Enum>, Enum), getCompressedValue(EnumState<E>, Class) etc to access the enums and booleans stored in this value. 

Representing enum values by their ordinal value is acceptable for our case as this value itself is never
serialized or deserialized and thus is not affected should ordinal values change.
/**
	 * Holds several boolean and enum typed attributes in a very compact manner. Enum values are stored in 4 bits
	 * (where 0 represents {@code null}, and each enum value is represented by its ordinal value + 1), thus allowing
	 * for up to 15 values per enum. Boolean values are stored in one bit.
	 * <p>
	 * The value is structured as follows:
	 *
	 * <pre>
	 * 1 - Lock mode
	 * 2 - Status
	 * 3 - Previous Status
	 * 4 - existsInDatabase
	 * 5 - isBeingReplicated
	 * 6 - loadedWithLazyPropertiesUnfetched; NOTE: this is not updated when properties are fetched lazily!
	 *
	 * 0000 0000 | 0000 0000 | 0654 3333 | 2222 1111
	 * </pre>
	 * Use {@link #setCompressedValue(org.hibernate.engine.spi.EntityEntry.EnumState, Enum)},
	 * {@link #getCompressedValue(org.hibernate.engine.spi.EntityEntry.EnumState, Class)} etc
	 * to access the enums and booleans stored in this value.
	 * <p>
	 * Representing enum values by their ordinal value is acceptable for our case as this value itself is never
	 * serialized or deserialized and thus is not affected should ordinal values change.
	 */
	private transient int compressedState;

	
Deprecated:
the tenantId and entityMode parameters where removed: this constructor accepts but ignores them.
Use the other constructor!/**
	 * @deprecated the tenantId and entityMode parameters where removed: this constructor accepts but ignores them.
	 * Use the other constructor!
	 */
	@Deprecated
	public EntityEntry(
			final Status status,
			final Object[] loadedState,
			final Object rowId,
			final Serializable id,
			final Object version,
			final LockMode lockMode,
			final boolean existsInDatabase,
			final EntityPersister persister,
			final EntityMode entityMode,
			final String tenantId,
			final boolean disableVersionIncrement,
			final boolean lazyPropertiesAreUnfetched,
			final PersistenceContext persistenceContext) {
		this( status, loadedState, rowId, id, version, lockMode, existsInDatabase,
				persister,disableVersionIncrement, lazyPropertiesAreUnfetched, persistenceContext );
	}

	public EntityEntry(
			final Status status,
			final Object[] loadedState,
			final Object rowId,
			final Serializable id,
			final Object version,
			final LockMode lockMode,
			final boolean existsInDatabase,
			final EntityPersister persister,
			final boolean disableVersionIncrement,
			final boolean lazyPropertiesAreUnfetched,
			final PersistenceContext persistenceContext) {
		setCompressedValue( EnumState.STATUS, status );
		// not useful strictly speaking but more explicit
		setCompressedValue( EnumState.PREVIOUS_STATUS, null );
		// only retain loaded state if the status is not Status.READ_ONLY
		if ( status != Status.READ_ONLY ) {
			this.loadedState = loadedState;
		}
		this.id=id;
		this.rowId=rowId;
		setCompressedValue( BooleanState.EXISTS_IN_DATABASE, existsInDatabase );
		this.version=version;
		setCompressedValue( EnumState.LOCK_MODE, lockMode );
		setCompressedValue( BooleanState.IS_BEING_REPLICATED, disableVersionIncrement );
		setCompressedValue( BooleanState.LOADED_WITH_LAZY_PROPERTIES_UNFETCHED, lazyPropertiesAreUnfetched );
		this.persister=persister;
		this.persistenceContext = persistenceContext;
	}

	
This for is used during custom deserialization handling
/**
	 * This for is used during custom deserialization handling
	 */
	@SuppressWarnings( {"JavaDoc"})
	private EntityEntry(
			final SessionFactoryImplementor factory,
			final String entityName,
			final Serializable id,
			final Status status,
			final Status previousStatus,
			final Object[] loadedState,
			final Object[] deletedState,
			final Object version,
			final LockMode lockMode,
			final boolean existsInDatabase,
			final boolean isBeingReplicated,
			final boolean loadedWithLazyPropertiesUnfetched,
			final PersistenceContext persistenceContext) {
		this.persister = ( factory == null ? null : factory.getEntityPersister( entityName ) );
		this.id = id;
		setCompressedValue( EnumState.STATUS, status );
		setCompressedValue( EnumState.PREVIOUS_STATUS, previousStatus );
		this.loadedState = loadedState;
		setDeletedState( deletedState );
		this.version = version;
		setCompressedValue( EnumState.LOCK_MODE, lockMode );
		setCompressedValue( BooleanState.EXISTS_IN_DATABASE, existsInDatabase );
		setCompressedValue( BooleanState.IS_BEING_REPLICATED, isBeingReplicated );
		setCompressedValue( BooleanState.LOADED_WITH_LAZY_PROPERTIES_UNFETCHED, loadedWithLazyPropertiesUnfetched );
		this.rowId = null; // this is equivalent to the old behavior...
		this.persistenceContext = persistenceContext;
	}

	public LockMode getLockMode() {
		return getCompressedValue( EnumState.LOCK_MODE );
	}

	public void setLockMode(LockMode lockMode) {
		setCompressedValue( EnumState.LOCK_MODE, lockMode );
	}

	public Status getStatus() {
		return getCompressedValue( EnumState.STATUS );
	}

	private Status getPreviousStatus() {
		return getCompressedValue( EnumState.PREVIOUS_STATUS );
	}

	public void setStatus(Status status) {
		if ( status == Status.READ_ONLY ) {
			//memory optimization
			loadedState = null;
		}

		Status currentStatus = this.getStatus();

		if ( currentStatus != status ) {
			setCompressedValue( EnumState.PREVIOUS_STATUS, currentStatus );
			setCompressedValue( EnumState.STATUS, status );
		}
	}

	public Serializable getId() {
		return id;
	}

	public Object[] getLoadedState() {
		return loadedState;
	}

	private static final Object[] DEFAULT_DELETED_STATE = null;

	public Object[] getDeletedState() {
		EntityEntryExtraStateHolder extra = getExtraState( EntityEntryExtraStateHolder.class );
		return extra != null ? extra.getDeletedState() : DEFAULT_DELETED_STATE;
	}

	public void setDeletedState(Object[] deletedState) {
		EntityEntryExtraStateHolder extra = getExtraState( EntityEntryExtraStateHolder.class );
		if ( extra == null && deletedState == DEFAULT_DELETED_STATE ) {
			//this is the default value and we do not store the extra state
			return;
		}
		if ( extra == null ) {
			extra = new EntityEntryExtraStateHolder();
			addExtraState( extra );
		}
		extra.setDeletedState( deletedState );
	}

	public boolean isExistsInDatabase() {
		return getCompressedValue( BooleanState.EXISTS_IN_DATABASE );
	}

	public Object getVersion() {
		return version;
	}

	public EntityPersister getPersister() {
		return persister;
	}

	
Get the EntityKey based on this EntityEntry.
Throws:
IllegalStateException – if getId() is null
Returns:
the EntityKey/**
	 * Get the EntityKey based on this EntityEntry.
	 * @return the EntityKey
	 * @throws  IllegalStateException if getId() is null
	 */
	public EntityKey getEntityKey() {
		if ( cachedEntityKey == null ) {
			if ( getId() == null ) {
				throw new IllegalStateException( "cannot generate an EntityKey when id is null.");
			}
			cachedEntityKey = new EntityKey( getId(), getPersister() );
		}
		return cachedEntityKey;
	}

	public String getEntityName() {
		return persister == null ? null : persister.getEntityName();

	}

	public boolean isBeingReplicated() {
		return getCompressedValue( BooleanState.IS_BEING_REPLICATED );
	}

	public Object getRowId() {
		return rowId;
	}

	
Handle updating the internal state of the entry after actually performing
the database update.  Specifically we update the snapshot information and
escalate the lock mode
Params:
entity – The entity instance
updatedState – The state calculated after the update (becomes the new loaded state.
nextVersion – The new version./**
	 * Handle updating the internal state of the entry after actually performing
	 * the database update.  Specifically we update the snapshot information and
	 * escalate the lock mode
	 *
	 * @param entity The entity instance
	 * @param updatedState The state calculated after the update (becomes the
	 * new {@link #getLoadedState() loaded state}.
	 * @param nextVersion The new version.
	 */
	public void postUpdate(Object entity, Object[] updatedState, Object nextVersion) {
		this.loadedState = updatedState;
		setLockMode( LockMode.WRITE );

		if ( getPersister().isVersioned() ) {
			this.version = nextVersion;
			getPersister().setPropertyValue( entity, getPersister().getVersionProperty(), nextVersion );
		}

		if ( getPersister().getInstrumentationMetadata().isInstrumented() ) {
			final FieldInterceptor interceptor = getPersister().getInstrumentationMetadata().extractInterceptor( entity );
			if ( interceptor != null ) {
				interceptor.clearDirty();
			}
		}

		if( entity instanceof SelfDirtinessTracker) {
			((SelfDirtinessTracker) entity).$$_hibernate_clearDirtyAttributes();
		}

		persistenceContext.getSession()
				.getFactory()
				.getCustomEntityDirtinessStrategy()
				.resetDirty( entity, getPersister(), (Session) persistenceContext.getSession() );
	}

	
After actually deleting a row, record the fact that the instance no longer
exists in the database
/**
	 * After actually deleting a row, record the fact that the instance no longer
	 * exists in the database
	 */
	public void postDelete() {
		setCompressedValue( EnumState.PREVIOUS_STATUS, getStatus() );
		setCompressedValue( EnumState.STATUS, Status.GONE );
		setCompressedValue( BooleanState.EXISTS_IN_DATABASE, false );
	}

	
After actually inserting a row, record the fact that the instance exists on the
database (needed for identity-column key generation)
/**
	 * After actually inserting a row, record the fact that the instance exists on the
	 * database (needed for identity-column key generation)
	 */
	public void postInsert(Object[] insertedState) {
		setCompressedValue( BooleanState.EXISTS_IN_DATABASE, true );
	}

	public boolean isNullifiable(boolean earlyInsert, SessionImplementor session) {
		if ( getStatus() == Status.SAVING ) {
			return true;
		}
		else if ( earlyInsert ) {
			return !isExistsInDatabase();
		}
		else {
			return session.getPersistenceContext().getNullifiableEntityKeys().contains( getEntityKey() );
		}
	}

	public Object getLoadedValue(String propertyName) {
		if ( loadedState == null || propertyName == null ) {
			return null;
		}
		else {
			int propertyIndex = ( (UniqueKeyLoadable) persister ).getPropertyIndex( propertyName );
			return loadedState[propertyIndex];
		}
	}

	
Not sure this is the best method name, but the general idea here is to return true if the entity can possibly be dirty. This can only be the case if it is in a modifiable state (not read-only/deleted) and it either has mutable properties or field-interception is not telling us it is dirty. Clear as mud? :/ A name like canPossiblyBeDirty might be better 
Params:
entity – The entity to test
Returns:
true indicates that the entity could possibly be dirty and that dirty check should happen; false indicates there is no way the entity can be dirty/**
	 * Not sure this is the best method name, but the general idea here is to return {@code true} if the entity can
	 * possibly be dirty.  This can only be the case if it is in a modifiable state (not read-only/deleted) and it
	 * either has mutable properties or field-interception is not telling us it is dirty.  Clear as mud? :/
	 *
	 * A name like canPossiblyBeDirty might be better
	 *
	 * @param entity The entity to test
	 *
	 * @return {@code true} indicates that the entity could possibly be dirty and that dirty check
	 * should happen; {@code false} indicates there is no way the entity can be dirty
	 */
	public boolean requiresDirtyCheck(Object entity) {
		return isModifiableEntity()
				&& ( !isUnequivocallyNonDirty( entity ) );
	}

	@SuppressWarnings( {"SimplifiableIfStatement"})
	private boolean isUnequivocallyNonDirty(Object entity) {

		if(entity instanceof SelfDirtinessTracker)
			return ((SelfDirtinessTracker) entity).$$_hibernate_hasDirtyAttributes();

		final CustomEntityDirtinessStrategy customEntityDirtinessStrategy =
				persistenceContext.getSession().getFactory().getCustomEntityDirtinessStrategy();
		if ( customEntityDirtinessStrategy.canDirtyCheck( entity, getPersister(), (Session) persistenceContext.getSession() ) ) {
			return ! customEntityDirtinessStrategy.isDirty( entity, getPersister(), (Session) persistenceContext.getSession() );
		}

		if ( getPersister().hasMutableProperties() ) {
			return false;
		}

		if ( getPersister().getInstrumentationMetadata().isInstrumented() ) {
			// the entity must be instrumented (otherwise we cant check dirty flag) and the dirty flag is false
			return ! getPersister().getInstrumentationMetadata().extractInterceptor( entity ).isDirty();
		}

		return false;
	}

	
Can the entity be modified?
The entity is modifiable if all of the following are true:

the entity class is mutable
the entity is not read-only
if the current status is Status.DELETED, then the entity was not read-only when it was deleted

Returns:
true, if the entity is modifiable; false, otherwise,/**
	 * Can the entity be modified?
	 *
	 * The entity is modifiable if all of the following are true:
	 * <ul>
	 * <li>the entity class is mutable</li>
	 * <li>the entity is not read-only</li>
	 * <li>if the current status is Status.DELETED, then the entity was not read-only when it was deleted</li>
	 * </ul>
	 * @return true, if the entity is modifiable; false, otherwise,
	 */
	public boolean isModifiableEntity() {
		Status status = getStatus();
		Status previousStatus = getPreviousStatus();
		return getPersister().isMutable()
				&& status != Status.READ_ONLY
				&& ! ( status == Status.DELETED && previousStatus == Status.READ_ONLY );
	}

	public void forceLocked(Object entity, Object nextVersion) {
		version = nextVersion;
		loadedState[ persister.getVersionProperty() ] = version;
		// TODO:  use LockMode.PESSIMISTIC_FORCE_INCREMENT
		//noinspection deprecation
		setLockMode( LockMode.FORCE );
		persister.setPropertyValue( entity, getPersister().getVersionProperty(), nextVersion );
	}

	public boolean isReadOnly() {
		Status status = getStatus();
		if (status != Status.MANAGED && status != Status.READ_ONLY) {
			throw new HibernateException("instance was not in a valid state");
		}
		return status == Status.READ_ONLY;
	}

	public void setReadOnly(boolean readOnly, Object entity) {
		if ( readOnly == isReadOnly() ) {
			// simply return since the status is not being changed
			return;
		}
		if ( readOnly ) {
			setStatus( Status.READ_ONLY );
			loadedState = null;
		}
		else {
			if ( ! persister.isMutable() ) {
				throw new IllegalStateException( "Cannot make an immutable entity modifiable." );
			}
			setStatus( Status.MANAGED );
			loadedState = getPersister().getPropertyValues( entity );
			persistenceContext.getNaturalIdHelper().manageLocalNaturalIdCrossReference(
					persister,
					id,
					loadedState,
					null,
					CachedNaturalIdValueSource.LOAD
			);
		}
	}

	@Override
	public String toString() {
		return "EntityEntry" +
				MessageHelper.infoString( getPersister().getEntityName(), id ) +
				'(' + getStatus() + ')';
	}

	public boolean isLoadedWithLazyPropertiesUnfetched() {
		return getCompressedValue( BooleanState.LOADED_WITH_LAZY_PROPERTIES_UNFETCHED );
	}

	
Custom serialization routine used during serialization of a
Session/PersistenceContext for increased performance.
Params:
oos – The stream to which we should write the serial data.
Throws:
IOException – If a stream error occurs/**
	 * Custom serialization routine used during serialization of a
	 * Session/PersistenceContext for increased performance.
	 *
	 * @param oos The stream to which we should write the serial data.
	 *
	 * @throws java.io.IOException If a stream error occurs
	 */
	public void serialize(ObjectOutputStream oos) throws IOException {
		Status previousStatus = getPreviousStatus();
		oos.writeObject( getEntityName() );
		oos.writeObject( id );
		oos.writeObject( getStatus().name() );
		oos.writeObject( (previousStatus == null ? "" : previousStatus.name()) );
		// todo : potentially look at optimizing these two arrays
		oos.writeObject( loadedState );
		oos.writeObject( getDeletedState() );
		oos.writeObject( version );
		oos.writeObject( getLockMode().toString() );
		oos.writeBoolean( isExistsInDatabase() );
		oos.writeBoolean( isBeingReplicated() );
		oos.writeBoolean( isLoadedWithLazyPropertiesUnfetched() );
	}

	
Custom deserialization routine used during deserialization of a
Session/PersistenceContext for increased performance.
Params:
ois – The stream from which to read the entry.
persistenceContext – The context being deserialized.
Throws:
IOException – If a stream error occurs
ClassNotFoundException – If any of the classes declared in the stream
cannot be found
Returns:
The deserialized EntityEntry/**
	 * Custom deserialization routine used during deserialization of a
	 * Session/PersistenceContext for increased performance.
	 *
	 * @param ois The stream from which to read the entry.
	 * @param persistenceContext The context being deserialized.
	 *
	 * @return The deserialized EntityEntry
	 *
	 * @throws IOException If a stream error occurs
	 * @throws ClassNotFoundException If any of the classes declared in the stream
	 * cannot be found
	 */
	public static EntityEntry deserialize(
			ObjectInputStream ois,
			PersistenceContext persistenceContext) throws IOException, ClassNotFoundException {
		String previousStatusString;
		return new EntityEntry(
				persistenceContext.getSession().getFactory(),
				(String) ois.readObject(),
				(Serializable) ois.readObject(),
				Status.valueOf( (String) ois.readObject() ),
				( previousStatusString = (String) ois.readObject() ).length() == 0
						? null
						: Status.valueOf( previousStatusString ),
				(Object[]) ois.readObject(),
				(Object[]) ois.readObject(),
				ois.readObject(),
				LockMode.valueOf( (String) ois.readObject() ),
				ois.readBoolean(),
				ois.readBoolean(),
				ois.readBoolean(),
				persistenceContext
		);
	}

	//the following methods are handling extraState contracts.
	//they are not shared by a common superclass to avoid alignment padding
	//we are trading off duplication for padding efficiency
	public void addExtraState(EntityEntryExtraState extraState) {
		if ( next == null ) {
			next = extraState;
		}
		else {
			next.addExtraState( extraState );
		}
	}

	public <T extends EntityEntryExtraState> T getExtraState(Class<T> extraStateType) {
		if ( next == null ) {
			return null;
		}
		if ( extraStateType.isAssignableFrom( next.getClass() ) ) {
			return (T) next;
		}
		else {
			return next.getExtraState( extraStateType );
		}
	}
	
Saves the value for the given enum property.
Params:
state – 
           identifies the value to store
value – 
           the value to store; The caller must make sure that it matches
           the given identifier/**
	 * Saves the value for the given enum property.
	 *
	 * @param state
	 *            identifies the value to store
	 * @param value
	 *            the value to store; The caller must make sure that it matches
	 *            the given identifier
	 */
	private <E extends Enum<E>> void setCompressedValue(EnumState<E> state, E value) {
		// reset the bits for the given property to 0
		compressedState &= state.getUnsetMask();
		// store the numeric representation of the enum value at the right offset
		compressedState |= ( state.getValue( value ) << state.getOffset() );
	}

	
Gets the current value of the given enum property.
Params:
state – 
           identifies the value to store
Returns:
the current value of the specified property/**
	 * Gets the current value of the given enum property.
	 *
	 * @param state
	 *            identifies the value to store
	 * @return the current value of the specified property
	 */
	private <E extends Enum<E>> E getCompressedValue(EnumState<E> state) {
		// restore the numeric value from the bits at the right offset and return the corresponding enum constant
		int index = ( ( compressedState & state.getMask() ) >> state.getOffset() ) - 1;
		return index == - 1 ? null : state.getEnumConstants()[index];
	}

	
Saves the value for the given boolean flag.
Params:
state – 
           identifies the value to store
value – 
           the value to store/**
	 * Saves the value for the given boolean flag.
	 *
	 * @param state
	 *            identifies the value to store
	 * @param value
	 *            the value to store
	 */
	private void setCompressedValue(BooleanState state, boolean value) {
		compressedState &= state.getUnsetMask();
		compressedState |= ( state.getValue( value ) << state.getOffset() );
	}

	
Gets the current value of the given boolean flag.
Params:
state – 
           identifies the value to store
Returns:
the current value of the specified flag/**
	 * Gets the current value of the given boolean flag.
	 *
	 * @param state
	 *            identifies the value to store
	 * @return the current value of the specified flag
	 */
	private boolean getCompressedValue(BooleanState state) {
		return ( ( compressedState & state.getMask() ) >> state.getOffset() ) == 1;
	}

	
Represents an enum value stored within a number value, using four bits starting at a specified offset.
Author:
Gunnar Morling/**
	 * Represents an enum value stored within a number value, using four bits starting at a specified offset.
	 *
	 * @author Gunnar Morling
	 */
	private static class EnumState<E extends Enum<E>> {

		private static final EnumState<LockMode> LOCK_MODE = new EnumState<LockMode>( 0, LockMode.class );
		private static final EnumState<Status> STATUS = new EnumState<Status>( 4, Status.class );
		private static final EnumState<Status> PREVIOUS_STATUS = new EnumState<Status>( 8, Status.class );

		private final int offset;
		private final E[] enumConstants;
		private final int mask;
		private final int unsetMask;

		private EnumState(int offset, Class<E> enumType) {
			E[] enumConstants = enumType.getEnumConstants();

			// In case any of the enums cannot be stored in 4 bits anymore, we'd have to re-structure the compressed
			// state int
			if ( enumConstants.length > 15 ) {
				throw new AssertionFailure( "Cannot store enum type " + enumType.getName() + " in compressed state as"
						+ " it has too many values." );
			}

			this.offset = offset;
			this.enumConstants = enumConstants;

			// a mask for reading the four bits, starting at the right offset
			this.mask = 0xF << offset;

			// a mask for setting the four bits at the right offset to 0
			this.unsetMask = 0xFFFF & ~mask;
		}

		
Returns the numeric value to be stored for the given enum value.
/**
		 * Returns the numeric value to be stored for the given enum value.
		 */
		private int getValue(E value) {
			return value != null ? value.ordinal() + 1 : 0;
		}

		
Returns the offset within the number value at which this enum value is stored.
/**
		 * Returns the offset within the number value at which this enum value is stored.
		 */
		private int getOffset() {
			return offset;
		}

		
Returns the bit mask for reading this enum value from the number value storing it.
/**
		 * Returns the bit mask for reading this enum value from the number value storing it.
		 */
		private int getMask() {
			return mask;
		}

		
Returns the bit mask for resetting this enum value from the number value storing it.
/**
		 * Returns the bit mask for resetting this enum value from the number value storing it.
		 */
		private int getUnsetMask() {
			return unsetMask;
		}

		
Returns the constants of the represented enum which is cached for performance reasons.
/**
		 * Returns the constants of the represented enum which is cached for performance reasons.
		 */
		private E[] getEnumConstants() {
			return enumConstants;
		}
	}

	
Represents a boolean flag stored within a number value, using one bit at a specified offset.
Author:
Gunnar Morling/**
	 * Represents a boolean flag stored within a number value, using one bit at a specified offset.
	 *
	 * @author Gunnar Morling
	 */
	private enum BooleanState {

		EXISTS_IN_DATABASE(13),
		IS_BEING_REPLICATED(14),
		LOADED_WITH_LAZY_PROPERTIES_UNFETCHED(15);

		private final int offset;
		private final int mask;
		private final int unsetMask;

		private BooleanState(int offset) {
			this.offset = offset;
			this.mask = 0x1 << offset;
			this.unsetMask = 0xFFFF & ~mask;
		}

		private int getValue(boolean value) {
			return value ? 1 : 0;
		}

		
Returns the offset within the number value at which this boolean flag is stored.
/**
		 * Returns the offset within the number value at which this boolean flag is stored.
		 */
		private int getOffset() {
			return offset;
		}

		
Returns the bit mask for reading this flag from the number value storing it.
/**
		 * Returns the bit mask for reading this flag from the number value storing it.
		 */
		private int getMask() {
			return mask;
		}

		
Returns the bit mask for resetting this flag from the number value storing it.
/**
		 * Returns the bit mask for resetting this flag from the number value storing it.
		 */
		private int getUnsetMask() {
			return unsetMask;
		}
	}
}