Copyright (c) 2004, 2018 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2004, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.registry;

An object which has the general characteristics of all the nestable elements
in a plug-in manifest.
/**
 * An object which has the general characteristics of all the nestable elements
 * in a plug-in manifest.
 */
public abstract class RegistryObject implements KeyedElement {
	//Object identifier
	private int objectId = RegistryObjectManager.UNKNOWN;
	//The children of the element
	protected int[] children = RegistryObjectManager.EMPTY_INT_ARRAY;

	// The field combines offset, persistence flag, and no offset flag
	private int extraDataOffset = EMPTY_MASK;

	// it is assumed that int has 32 bits (bits #0 to #31);
	// bits #0 - #29 are the offset (limited to about 1Gb)
	// bit #30 - persistance flag
	// bit #31 - registry object has no extra data offset
	// the bit#31 is a sign bit; bit#30 is the highest mantissa bit
	static final int EMPTY_MASK = 0x80000000; // only taking bit #31
	static final int PERSIST_MASK = 0x40000000; // only taking bit #30
	static final int OFFSET_MASK = 0x3FFFFFFF; // all bits but #30, #31

	//The registry that owns this object
	protected ExtensionRegistry registry;

	protected RegistryObject(ExtensionRegistry registry, boolean persist) {
		this.registry = registry;
		setPersist(persist);
	}

	void setRawChildren(int[] values) {
		children = values;
	}

	//This can not return null. It returns the singleton empty array or an array
	protected int[] getRawChildren() {
		return children;
	}

	void setObjectId(int value) {
		objectId = value;
	}

	protected int getObjectId() {
		return objectId;
	}

	//Implementation of the KeyedElement interface
	@Override
	public int getKeyHashCode() {
		return objectId;
	}

	@Override
	public Object getKey() {
		return Integer.valueOf(objectId);
	}

	@Override
	public boolean compare(KeyedElement other) {
		return objectId == ((RegistryObject) other).objectId;
	}

	protected boolean shouldPersist() {
		return (extraDataOffset & PERSIST_MASK) == PERSIST_MASK;
	}

	private void setPersist(boolean persist) {
		if (persist)
			extraDataOffset |= PERSIST_MASK;
		else
			extraDataOffset &= ~PERSIST_MASK;
	}

	protected boolean noExtraData() {
		return (extraDataOffset & EMPTY_MASK) == EMPTY_MASK;
	}

	// Convert no extra data to -1 on output
	protected int getExtraDataOffset() {
		if (noExtraData())
			return -1;
		return extraDataOffset & OFFSET_MASK;
	}

	// Accept -1 as "no extra data" on input
	protected void setExtraDataOffset(int offset) {
		if (offset == -1) {
			extraDataOffset &= ~OFFSET_MASK; // clear all offset bits
			extraDataOffset |= EMPTY_MASK;
			return;
		}

		if ((offset & OFFSET_MASK) != offset)
			throw new IllegalArgumentException("Registry object: extra data offset is out of range"); //$NON-NLS-1$

		extraDataOffset &= ~(OFFSET_MASK | EMPTY_MASK); // clear all offset bits; mark as non-empty
		extraDataOffset |= (offset & OFFSET_MASK); // set all offset bits
	}

	protected String getLocale() {
		return registry.getLocale();
	}
}