StringSpan.java

/* Copyright (C) 2002 Univ. of Massachusetts Amherst, Computer Science Dept.
   This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
   http://www.cs.umass.edu/~mccallum/mallet
   This software is provided under the terms of the Common Public License,
   version 1.0, as published by http://www.opensource.org.  For further
   information, see the file `LICENSE' included with this distribution. */

/** 
 @author Andrew McCallum <a href="mailto:mccallum@cs.umass.edu">mccallum@cs.umass.edu</a>
 */

package edu.nd.nina.extract;

import edu.nd.nina.types.Token;

/** A sub-section of a linear string. */

public class StringSpan extends Token implements Span {
	private CharSequence document; // The larger string of which this is a span.
	private int start, end;

	public StringSpan(CharSequence doc, int start, int end) {
		super(constructTokenText(doc, start, end));
		this.document = doc;
		this.start = start;
		this.end = end;
	}

	public Span intersection(Span r) {
		StringSpan other = (StringSpan) r;
		int newStart = Math.max(start, other.start);
		int newEnd = Math.min(end, other.end);
		return new StringSpan(document, newStart, newEnd);
	}

	private static String constructTokenText(CharSequence doc, int start,
			int end) {
		CharSequence subseq = doc.subSequence(start, end);
		return subseq.toString();
	}

	public Object getDocument() {
		return document;
	}

	public boolean intersects(Span r) {
		if (!(r instanceof StringSpan))
			return false;
		StringSpan sr = (StringSpan) r;
		return (sr.document == this.document && !(sr.end < this.start || sr.start > this.end));
	}

	public boolean isSubspan(Span r) {
		return (r.getDocument() == this.document
				&& (this.start <= r.getStartIdx()) && (r.getEndIdx() <= this.end));
	}

	public int getStartIdx() {
		return start;
	}

	public int getEndIdx() {
		return end;
	}

	public String toString() {
		return super.toString() + "  span[" + start + ".." + end + "]";
	}

}