jcommons/org.eclipse.statet.jcommons.util/src/org/eclipse/statet/jcommons/collections/IntIntervalArrays.java

/*=============================================================================#
 # Copyright (c) 2019, 2020 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.jcommons.collections;

import java.util.Arrays;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;


/**
 * For integer arrays with distinguish intervals in increasing order:
 * [startOffset<sub>0</sub>, endOffset<sub>0</sub>), [startOffset<sub>1</sub>, endOffset<sub>2</sub>), ...
 */
@NonNullByDefault
public class IntIntervalArrays {
	
	
	/**
	 * Inserts blank (non-marked range).
	 * 
	 * The method may changed the array specified by <code>regions</code>!
	 * 
	 * @param regions the regions
	 * @param offset the offset of the blank to insert
	 * @param length the length of the blank to insert
	 * @return
	 */
	public static int[] insertBlank(int[] regions, final int offset, final int length) {
		int i= 0;
		for (;; i++) {
			if (i >= regions.length) {
				return regions;
			}
			if (regions[i] < offset) {
				continue;
			}
			else {
				break;
			}
		}
		if (i % 2 == 1) { // region is open
			if (regions[i] == offset) { // -> merge
				i++;
			}
			else /*(regions[i] > startOffset)*/ { // -> split region
				regions= Arrays.copyOf(regions, regions.length + 2);
				System.arraycopy(regions, i, regions, i + 2, regions.length - (i + 2));
				regions[i++]= offset;
				regions[i++]= offset + length;
			}
		}
		while (i < regions.length) {
			regions[i++]+= length;
		}
		return regions;
	}
	
	/**
	 * Inserts region (marked range).
	 * 
	 * The method may changed the array specified by <code>regions</code>!
	 * 
	 * @param regions the regions
	 * @param offset the offset of the region to insert
	 * @param length the length of the region to insert
	 * @return
	 */
	public static int[] insertRegion(int[] regions, final int offset, final int length) {
		int i= 0;
		for (;; i++) {
			if (i >= regions.length) { // -> append new region
				regions= Arrays.copyOf(regions, regions.length + 2);
				regions[i++]= offset;
				regions[i++]= offset + length;
				return regions;
			}
			if (regions[i] < offset) {
				continue;
			}
			else {
				break;
			}
		}
		if (i % 2 == 0) { // no region open
			if (regions[i] == offset) { // -> merge
				i++;
			}
			else /*(regions[i] > startOffset)*/ { // -> insert region
				regions= Arrays.copyOf(regions, regions.length + 2);
				System.arraycopy(regions, i, regions, i + 2, regions.length - (i + 2));
				regions[i++]= offset;
				regions[i++]= offset + length;
			}
		}
		while (i < regions.length) {
			regions[i++]+= length;
		}
		return regions;
	}
	
	/**
	 * Removes regions (marked ranges) behind the specified offset.
	 * 
	 * The method may changed the array specified by <code>regions</code>!
	 * 
	 * @param regions the regions
	 * @param offset the offset
	 * @return
	 */
	public static int[] removeTail(int[] regions, final int offset) {
		int i= 0;
		for (;; i++) {
			if (i >= regions.length) {
				return regions;
			}
			if (regions[i] < offset) {
				continue;
			}
			else {
				break;
			}
		}
		if (i % 2 == 1) { // region is open
			regions[i]= offset;
			i++;
		}
		if (i < regions.length) {
			regions= Arrays.copyOf(regions, i);
		}
		return regions;
	}
	
	
	private IntIntervalArrays() {
	}
	
}