org.eclipse.text/src/org/eclipse/jface/text/Position.java

/**********************************************************************
Copyright (c) 2000, 2002 IBM Corp. and others.
All rights reserved. This program and the accompanying materials
are made available under the terms of the Common Public License v1.0
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/cpl-v10.html

Contributors:
    IBM Corporation - Initial implementation
**********************************************************************/

package org.eclipse.jface.text;

 
/**
 * Positions describe text ranges of a document and are
 * adapted to changes applied to that document. The text range 
 * is specified by an offset and a length. Positions can be marked as
 * deleted. Deleted positions are considered to no longer represent 
 * a valid text range in the managing document. <p>
 * Positions attached to documents are ususally updated by position updaters.
 * Because position updaters are freely defineable and because of the
 * frequence in which they are used, the fields of a position are made
 * publicly accessible. Clients other than position updaters are not 
 * allowed to access these public fields.
 *
 * @see IDocument
 */
public class Position {
	
	/** The offset of the position */
	public int offset;
	/** The length of the position */
	public int length;
	/** Indicates whether the position has been deleted */
	public boolean isDeleted;
	
	/**
	 * Creates a new position with the given offset and length 0.
	 *
	 * @param offset the position offset, must be >= 0
	 */
	public Position(int offset) {
		this(offset, 0);
	}
	
	/**
	 * Creates a new position with the given offset and length.
	 *
	 * @param offset the position offset, must be >= 0
	 * @param length the position length, must be >= 0
	 */
	public Position(int offset, int length) {
		Assert.isTrue(offset >= 0);
		Assert.isTrue(length >= 0);
		this.offset= offset;
		this.length= length;
	}
	
	/*
	 * @see Object#hashCode
	 */
	 public int hashCode() {
	 	int deleted= isDeleted ? 0 : 1;
	 	return (offset << 24) | (length << 16) | deleted;
	 }
	
	/**
	 * Marks this position as deleted.
	 */
	public void delete() {
		isDeleted= true;
	}
	
	/**
	 * Marks this position as not deleted.
	 * @since 2.0
	 */
	public void undelete() {
		isDeleted= false;
	}
	
	/*
	 * @see Object#equals
	 */
	public boolean equals(Object other) {
		if (other instanceof Position) {
			Position rp= (Position) other;
			return (rp.offset == offset) && (rp.length == length);
		}
		return super.equals(other);
	}
		
	/**
	 * Returns the length of this position.
	 *
	 * @return the length of this position
	 */
	public int getLength() {
		return length;
	}
	
	/**
	 * Returns the offset of this position.
	 *
	 * @return the length of this position
	 */
	public int getOffset() {
		return offset;
	}
	
	/**
	 * Checks whether the given offset is inside
	 * of this position's text range.
	 *
	 * @param offset the offset to check
	 * @return <code>true</code> if offset is inside of this position 
	 */
	public boolean includes(int offset) {
		
		if (isDeleted)
			return false;
			
		return (this.offset <= offset) && (offset < this.offset + length);
	}
	
	/**
	 * Checks whether the intersection of the given text range
	 * and the text range represented by this position is empty
	 * or not.
	 *
	 * @param offset the offset of the range to check
	 * @param length the length of the range to check
	 * @return <code>true</code> if intersection is not empty
	 */
	public boolean overlapsWith(int offset, int length) {
		
		if (isDeleted)
			return false;
			
		int end= offset + length;
		int thisEnd= this.offset + this.length;
		
		if (length > 0) {
			if (this.length > 0)
				return this.offset < end && offset < thisEnd;
			return  offset <= this.offset && this.offset < end;
		}
		
		if (this.length > 0)
			return this.offset <= offset && offset < thisEnd;
		return this.offset == offset;
	}
	
	/**
	 * Returns whether this position has been deleted or not.
	 *
	 * @return <code>true</code> if position has been deleted
	 */
	public boolean isDeleted() {
		return isDeleted;
	}
	
	/**
	 * Changes the length of this position to the given length.
	 *
	 * @param length the new length of this position
	 */
	public void setLength(int length) {
		this.length= length;
	}
	
	/**
	 * Changes the offset of this position to the given offset.
	 *
	 * @param offset the new offset of this position
	 */
	public void setOffset(int offset) {
		this.offset= offset;
	}
}