libjava/classpath/gnu/java/util/regex/BacktrackStack.java

/* gnu/regexp/BacktrackStack.java
   Copyright (C) 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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this exception to your version of the library, but you are not
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package gnu.java.util.regex;

/**
 * An instance of this class represents a stack
 * used for backtracking.
 *
 * @author Ito Kazumitsu</A>
 */
final class BacktrackStack
{

    /** A set of data to be used for backtracking. */
  static class Backtrack
  {
        /** REToken to which to go back */
    REToken token;
        /** CharIndexed on which matches are being searched for. */
    CharIndexed input;
        /** REMatch to be used by the REToken token. */
    REMatch match;
        /** Some parameter used by the token's backtrack method. */
    Object param;
      Backtrack (REToken token, CharIndexed input, REMatch match,
                 Object param)
    {
      this.token = token;
      this.input = input;
      //  REMatch may change before backtracking is needed. So we
      //  keep a clone of it.
      this.match = (REMatch) match.clone ();
      this.param = param;
    }
  }

  Backtrack[] stack;
  private int size;
  private int capacity;
  private static final int INITIAL_CAPACITY = 32;
  private static final int CAPACITY_INCREMENT = 16;

  BacktrackStack ()
  {
    stack = new Backtrack[INITIAL_CAPACITY];
    size = 0;
    capacity = INITIAL_CAPACITY;
  }

  boolean empty ()
  {
    return size == 0;
  }

  Backtrack peek ()
  {
    return stack[size - 1];
  }

  Backtrack pop ()
  {
    Backtrack bt = stack[--size];
    stack[size] = null;
    return bt;
  }

  void clear ()
  {
    for (int i = 0; i < size; i++)
      {
        stack[i] = null;
      }
    size = 0;
  }

  void push (Backtrack bt)
  {
    if (size >= capacity)
      {
        capacity += CAPACITY_INCREMENT;
        Backtrack[]newStack = new Backtrack[capacity];
        System.arraycopy (stack, 0, newStack, 0, size);
        stack = newStack;
      }
    stack[size++] = bt;
  }

}