/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
    *
    * All rights reserved. This program and the accompanying materials
    * are made available under the terms of the Eclipse Public License v1.0
    * which accompanies this distribution, and is available at
    * http://www.eclipse.org/legal/epl-v10.html
    *
    * Alternatively, the contents of this file may be used under the terms of
   * either the GNU Lesser General Public License Version 2.1 or later (the
   * "LGPL"), in which case the provisions of the LGPL are applicable instead
   * of those above. If you wish to allow use of your version of this file only
   * under the terms of the LGPL, and not to allow others to use your version of
   * this file under the terms of the EPL, indicate your decision by deleting
   * the provisions above and replace them with the notice and other provisions
   * required by the LGPL. If you do not delete the provisions above, a recipient
   * may use your version of this file under the terms of the EPL or the LGPL.
   * 
   * Based on the original MiniSat specification from:
   * 
   * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
   * Sixth International Conference on Theory and Applications of Satisfiability
   * Testing, LNCS 2919, pp 502-518, 2003.
   *
   * See www.minisat.se for the original solver in C++.
   * 
   *******************************************************************************/
  package org.sat4j.reader;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.Serializable;
  import java.math.BigInteger;
  
  /**
   * Efficient scanner based on the LecteurDimacs class written by Frederic
   * Laihem. It is much faster than Java Scanner class because it does not split
   * the input file into strings but reads and interpret the input char by char.
   * Furthermore, it is based on stream (char in ASCII) and not reader (word in
   * UTF).
   * 
   * @author laihem
   * @author leberre
   * @since 2.1
   */
  public class EfficientScanner implements Serializable {
  
  	private static final long serialVersionUID = 1L;
  
  	/* taille du buffer */
  	private final static int TAILLE_BUF = 16384;
  
  	private transient final BufferedInputStream in;
  
  	private static final char EOF = (char) -1;
  
  	private final char commentChar;
  
  	/*
  	 * nomFichier repr?sente le nom du fichier ? lire
  	 */
  	public EfficientScanner(final InputStream input, char commentChar) {
  		this.in = new BufferedInputStream(input, EfficientScanner.TAILLE_BUF);
  		this.commentChar = commentChar;
  	}
  
  	public EfficientScanner(final InputStream input) {
  		this(input, 'c');
  	}
  
  	public void close() throws IOException {
  		in.close();
  	}
  
  	/** Skip commented lines. */
  	public void skipComments() throws IOException {
  		char currentChar;
  		for (;;) {
  			currentChar = currentChar();
  			if (currentChar != commentChar) {
  				break;
  			}
  			skipRestOfLine();
  			if (currentChar == EOF)
  				break;
  		}
  	}
  
  	/**
  	 * To get the next available integer.
  	 * 
  	 * @return
  	 * @throws IOException
  	 * @throws ParseFormatException
  	 */
  	public int nextInt() throws IOException, ParseFormatException {
  		int val = 0;
  		boolean neg = false;
 		char currentChar = skipSpaces();
 		if (currentChar == '-') {
 			neg = true;
 			currentChar = (char) in.read();
 		} else if (currentChar == '+') {
 			currentChar = (char) in.read();
 		} else if (currentChar >= '0' && currentChar <= '9') {
 			val = currentChar - '0';
 			currentChar = (char) in.read();
 		} else {
 			throw new ParseFormatException("Unknown character " + currentChar);
 		}
 		/* on lit la suite du literal */
 		while (currentChar >= '0' && currentChar <= '9') {
 			val = (val * 10) + currentChar - '0';
 			currentChar = (char) in.read();
 		}
 		if (currentChar == '\r') {
 			in.read(); // skip \r\n on windows.
 		}
 		return neg ? -val : val;
 	}
 
 	public BigInteger nextBigInteger() throws IOException, ParseFormatException {
 		StringBuffer stb = new StringBuffer();
 		char currentChar = skipSpaces();
 		if (currentChar == '-') {
 			stb.append(currentChar);
 			currentChar = (char) in.read();
 		} else if (currentChar == '+') {
 			currentChar = (char) in.read();
 		} else if (currentChar >= '0' && currentChar <= '9') {
 			stb.append(currentChar);
 			currentChar = (char) in.read();
 		} else {
 			throw new ParseFormatException("Unknown character " + currentChar);
 		}
 		while (currentChar >= '0' && currentChar <= '9') {
 			stb.append(currentChar);
 			currentChar = (char) in.read();
 		}
 		return new BigInteger(stb.toString());
 	}
 
 	/**
 	 * @throws ParseFormatException
 	 *             never used in that method.
 	 */
 	public String next() throws IOException, ParseFormatException {
 		StringBuffer stb = new StringBuffer();
 		char currentChar = skipSpaces();
 		while (currentChar != ' ' && currentChar != '\n') {
 			stb.append(currentChar);
 			currentChar = (char) in.read();
 		}
 		return stb.toString();
 	}
 
 	public char skipSpaces() throws IOException {
 		char car;
 
 		do {
 			car = (char) in.read();
 		} while (car == ' ' || car == '\n');
 
 		return car;
 	}
 
 	public String nextLine() throws IOException {
 		StringBuffer stb = new StringBuffer();
 		char car;
 		do {
 			car = (char) in.read();
 			stb.append(car);
 		} while ((car != '\n') && (car != EOF));
 		return stb.toString();
 	}
 
 	public void skipRestOfLine() throws IOException {
 		char car;
 		do {
 			car = (char) in.read();
 		} while ((car != '\n') && (car != EOF));
 	}
 
 	public boolean eof() throws IOException {
 		return currentChar() == EOF;
 	}
 
 	public char currentChar() throws IOException {
 		in.mark(10);
 		char car = (char) in.read();
 		in.reset();
 		return car;
 	}
 }