content: /*
   * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package openjdk.tools.javac.parser;
  
  import java.nio.*;
  import java.util.List;
  import java.util.ArrayList;
  
  import openjdk.tools.javac.util.Position.LineMap;
  import openjdk.tools.javac.parser.JavaTokenizer.*;
  
  import static openjdk.tools.javac.parser.Tokens.*;
  
  /** The lexical analyzer maps an input stream consisting of
   *  ASCII characters and Unicode escapes into a token sequence.
   *
   *  <p><b>This is NOT part of any supported API.
   *  If you write code that depends on this, you do so at your own risk.
   *  This code and its internal interfaces are subject to change or
   *  deletion without notice.</b>
   */
  public class Scanner implements Lexer {
  
      private Tokens tokens;
  
      /** The token, set by nextToken().
       */
      private Token token;
  
      /** The previous token, set by nextToken().
       */
      private Token prevToken;
  
      /** Buffer of saved tokens (used during lookahead)
       */
      private List<Token> savedTokens = new ArrayList<>();
  
      private JavaTokenizer tokenizer;
  
      /**
       * Create a scanner from the input array.  This method might
       * modify the array.  To avoid copying the input array, ensure
       * that {@code inputLength < input.length} or
       * {@code input[input.length -1]} is a white space character.
       *
       * @param fac the factory which created this Scanner
       * @param buf the input, might be modified
       * Must be positive and less than or equal to input.length.
       */
      protected Scanner(ScannerFactory fac, CharBuffer buf) {
          this(fac, new JavaTokenizer(fac, buf));
      }
  
      protected Scanner(ScannerFactory fac, char[] buf, int inputLength) {
          this(fac, new JavaTokenizer(fac, buf, inputLength));
      }
  
      protected Scanner(ScannerFactory fac, JavaTokenizer tokenizer) {
          this.tokenizer = tokenizer;
          tokens = fac.tokens;
          token = prevToken = DUMMY;
      }
  
      public Token token() {
          return token(0);
      }
  
      public Token token(int lookahead) {
          if (lookahead == 0) {
              return token;
          } else {
              ensureLookahead(lookahead);
              return savedTokens.get(lookahead - 1);
          }
      }
      //where
          private void ensureLookahead(int lookahead) {
              for (int i = savedTokens.size() ; i < lookahead ; i ++) {
                  savedTokens.add(tokenizer.readToken());
              }
          }
  
      public Token prevToken() {
          return prevToken;
      }
  
      public void nextToken() {
          prevToken = token;
          if (!savedTokens.isEmpty()) {
              token = savedTokens.remove(0);
          } else {
              token = tokenizer.readToken();
          }
      }
  
      public Token split() {
          Token[] splitTokens = token.split(tokens);
          prevToken = splitTokens[0];
          token = splitTokens[1];
          return token;
      }
  
      public LineMap getLineMap() {
          return tokenizer.getLineMap();
      }
  
      public int errPos() {
          return tokenizer.errPos();
      }
  
      public void errPos(int pos) {
          tokenizer.errPos(pos);
      }
  
      public void seek(int seek) {
          assert seek >= 0;
          tokenizer.seek = seek;
      }
  }
  