Copyright (c) 2003, 2015 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 - Initial API and implementation
    James Blackburn (Broadcom Corp.) - ongoing development
    Lars Vogel  - Bug 473427
/*******************************************************************************
 * Copyright (c) 2003, 2015 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 - Initial API and implementation
 *     James Blackburn (Broadcom Corp.) - ongoing development
 *     Lars Vogel <Lars.Vogel@vogella.com> - Bug 473427
 *******************************************************************************/
package org.eclipse.core.internal.resources;

import java.util.*;
import org.eclipse.core.runtime.IPath;

The notification mechanism can request marker deltas for several overlapping intervals
of time. This class maintains a history of marker deltas, and upon request can
generate a map of marker deltas for any interval.  This is done by maintaining
batches of marker deltas keyed by the change Id at the start of that batch.
When the delta factory requests a delta, it specifies the start generation, and
this class assembles the deltas for all generations between then and the most
recent delta.
/**
 * The notification mechanism can request marker deltas for several overlapping intervals
 * of time. This class maintains a history of marker deltas, and upon request can
 * generate a map of marker deltas for any interval.  This is done by maintaining
 * batches of marker deltas keyed by the change Id at the start of that batch.
 * When the delta factory requests a delta, it specifies the start generation, and
 * this class assembles the deltas for all generations between then and the most
 * recent delta.
 */
class MarkerDeltaManager {
	private static final int DEFAULT_SIZE = 10;
	private long[] startIds = new long[DEFAULT_SIZE];
	@SuppressWarnings("unchecked")
	private Map<IPath, MarkerSet>[] batches = new Map[DEFAULT_SIZE];
	private int nextFree = 0;

	
Returns the deltas from the given start id up until the present. Returns null
if there are no deltas for that interval.
/**
	 * Returns the deltas from the given start id up until the present. Returns null
	 * if there are no deltas for that interval.
	 */
	protected Map<IPath, MarkerSet> assembleDeltas(long start) {
		Map<IPath, MarkerSet> result = null;
		for (int i = 0; i < nextFree; i++)
			if (startIds[i] >= start)
				result = MarkerDelta.merge(result, batches[i]);
		return result;
	}

	
Flushes all delta batches up to but not including the given start Id.
/**
	 * Flushes all delta batches up to but not including the given start Id.
	 */
	@SuppressWarnings("unchecked")
	protected void resetDeltas(long startId) {
		//find offset of first batch to keep
		int startOffset = 0;
		for (; startOffset < nextFree; startOffset++)
			if (startIds[startOffset] >= startId)
				break;
		if (startOffset == 0)
			return;
		long[] newIds = startIds;
		Map<IPath, MarkerSet>[] newBatches = batches;
		//shrink the arrays if it has grown too large
		if (startIds.length > DEFAULT_SIZE && (nextFree - startOffset < DEFAULT_SIZE)) {
			newIds = new long[DEFAULT_SIZE];
			newBatches = new Map[DEFAULT_SIZE];
		}
		//copy and compact into the new array
		int remaining = nextFree - startOffset;
		System.arraycopy(startIds, startOffset, newIds, 0, remaining);
		System.arraycopy(batches, startOffset, newBatches, 0, remaining);
		//clear the end of the array
		Arrays.fill(startIds, remaining, startIds.length, 0);
		Arrays.fill(batches, remaining, startIds.length, null);
		startIds = newIds;
		batches = newBatches;
		nextFree = remaining;
	}

	@SuppressWarnings("unchecked")
	protected Map<IPath, MarkerSet> newGeneration(long start) {
		int len = startIds.length;
		if (nextFree >= len) {
			long[] newIds = new long[len * 2];
			Map<IPath, MarkerSet>[] newBatches = new Map[len * 2];
			System.arraycopy(startIds, 0, newIds, 0, len);
			System.arraycopy(batches, 0, newBatches, 0, len);
			startIds = newIds;
			batches = newBatches;
		}
		startIds[nextFree] = start;
		batches[nextFree] = new HashMap<>(11);
		return batches[nextFree++];
	}
}