LookAheadPtr.java

package com.mathsolver.objects;

import com.mathsolver.utils.Scanner;

/**
 * Class to embody the structure of LookAheadPointer
 * 
 * 
 * @author zerosign <r1nlx0@gmail.com>
 *
 */
public class LookAheadPtr {
	private int start;
	private int counter;
	private CharSequence text;
	
	
	/**
	 * Constructor of this class
	 * counter always have an initial value zero
	 * 
	 * @param start start of the current CharacterSequence 
	 * @param text
	 */
	public LookAheadPtr(int start, CharSequence text) {
		super();
		this.start = start;
		this.text = text;
		this.counter = 0;
	}
	
	/**
	 * Method that get current position of lookahead
	 * pointer from underlying CharacterSequence
	 * 
	 * @return
	 */
	public int getPosition() {
		return start+counter;
	}

	/**
	 * Getter for counter variable
	 * 
	 * @return
	 */
	public int getCounter() {
		return counter;
	}
	
	
	/**
	 * Method to increment the counter as number
	 * 
	 * @param number
	 */
	public void incrementCounter(int number) {
		counter+= number;
	}
	
	/**
	 * Method to increment the counter post-increment by 1
	 * 
	 */
	public void incrementCounter() {
		counter++;
	}
	
	/**
	 * Method to decrement the counter post-decrement by 1
	 */
	public void decrementCounter() {
		counter--;
	}

	/**
	 * Method to increment start index post increment by number
	 * 
	 * @param number
	 */
	public void incrementStart(int number) {
		start+= number;
	}
	
	/**
	 * Method to increment start index post increment by 1
	 * 
	 */
	public void incrementStart() {
		start++;
	}
	
	/**
	 * Getter for start index in CharSequence
	 * 
	 * @return
	 */
	public int getStart() {
		return start;
	}

	/**
	 * Getter CharSequence of current lexeme
	 * computed from start index and counter value
	 * 
	 * @return
	 */
	public CharSequence getLexemeText() {
		return text.subSequence(start, start+counter);
	}
	
	/**
	 * Getter of current char by computing
	 * it from start and counter
	 * 
	 * 
	 * @return
	 */
	public char currentChar() {
		return text.charAt(start+counter);
	}

	/**
	 * Method to reset LookAheadPtr
	 * (reset start & counter value)
	 * 
	 */
	public void reset() {
		start = 0;
		counter = 0;
	}
	
	/**
	 * Method that increment the current start 
	 * to next start of lexeme. This method need to
	 * be called after lexeme is found in method
	 * {@link Scanner#scan(CharSequence) scan}
	 * 
	 * 
	 */
	public void next() {
		start += counter;
		counter = 0;
	}

	/**
	 * Getter of the length of CharSequence 
	 * 
	 * @return
	 */
	public int length() {
		return text.length();
	}

	
	
}