/*******************************************************************************
    * SAT4J: a SATisfiability library for Java Copyright (C) 2004, 2012 Artois University and CNRS
    *
    * 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++.
   *
   * Contributors:
   *   CRIL - initial API and implementation
   *******************************************************************************/
  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 static final int TAILLE_BUF = 16384;
  
      private final transient 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 {
          this.in.close();
      }
  
      /** Skip commented lines. */
      public void skipComments() throws IOException {
          char currentChar;
          for (;;) {
              currentChar = currentChar();
              if (currentChar != this.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) this.in.read();
         } else if (currentChar == '+') {
             currentChar = (char) this.in.read();
         } else if (currentChar >= '0' && currentChar <= '9') {
             val = currentChar - '0';
             currentChar = (char) this.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) this.in.read();
         }
         if (currentChar == '\r') {
             this.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) this.in.read();
         } else if (currentChar == '+') {
             currentChar = (char) this.in.read();
         } else if (currentChar >= '0' && currentChar <= '9') {
             stb.append(currentChar);
             currentChar = (char) this.in.read();
         } else {
             throw new ParseFormatException("Unknown character " + currentChar);
         }
         while (currentChar >= '0' && currentChar <= '9') {
             stb.append(currentChar);
             currentChar = (char) this.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) this.in.read();
         }
         return stb.toString();
     }
 
     public char skipSpaces() throws IOException {
         char car;
 
         do {
             car = (char) this.in.read();
         } while (car == ' ' || car == '\n');
 
         return car;
     }
 
     public String nextLine() throws IOException {
         StringBuffer stb = new StringBuffer();
         char car;
         do {
             car = (char) this.in.read();
             stb.append(car);
         } while (car != '\n' && car != EOF);
         return stb.toString();
     }
 
     public void skipRestOfLine() throws IOException {
         char car;
         do {
             car = (char) this.in.read();
         } while (car != '\n' && car != EOF);
     }
 
     public boolean eof() throws IOException {
         return currentChar() == EOF;
     }
 
     public char currentChar() throws IOException {
         this.in.mark(10);
         char car = (char) this.in.read();
         this.in.reset();
         return car;
     }
 }