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

   1 /* gnu/regexp/BacktrackStack.java
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38
  39 package gnu.java.util.regex;
  40
  41 /**
  42  * An instance of this class represents a stack
  43  * used for backtracking.
  44  *
  45  * @author Ito Kazumitsu</A>
  46  */
  47 final class BacktrackStack
  48 {
  49
  50     /** A set of data to be used for backtracking. */
  51   static class Backtrack
  52   {
  53         /** REToken to which to go back */
  54     REToken token;
  55         /** CharIndexed on which matches are being searched for. */
  56     CharIndexed input;
  57         /** REMatch to be used by the REToken token. */
  58     REMatch match;
  59         /** Some parameter used by the token's backtrack method. */
  60     Object param;
  61       Backtrack (REToken token, CharIndexed input, REMatch match,
  62                  Object param)
  63     {
  64       this.token = token;
  65       this.input = input;
  66       //  REMatch may change before backtracking is needed. So we
  67       //  keep a clone of it.
  68       this.match = (REMatch) match.clone ();
  69       this.param = param;
  70     }
  71   }
  72
  73   Backtrack[] stack;
  74   private int size;
  75   private int capacity;
  76   private static final int INITIAL_CAPACITY = 32;
  77   private static final int CAPACITY_INCREMENT = 16;
  78
  79   BacktrackStack ()
  80   {
  81     stack = new Backtrack[INITIAL_CAPACITY];
  82     size = 0;
  83     capacity = INITIAL_CAPACITY;
  84   }
  85
  86   boolean empty ()
  87   {
  88     return size == 0;
  89   }
  90
  91   Backtrack peek ()
  92   {
  93     return stack[size - 1];
  94   }
  95
  96   Backtrack pop ()
  97   {
  98     Backtrack bt = stack[--size];
  99     stack[size] = null;
 100     return bt;
 101   }
 102
 103   void clear ()
 104   {
 105     for (int i = 0; i < size; i++)
 106       {
 107         stack[i] = null;
 108       }
 109     size = 0;
 110   }
 111
 112   void push (Backtrack bt)
 113   {
 114     if (size >= capacity)
 115       {
 116         capacity += CAPACITY_INCREMENT;
 117         Backtrack[]newStack = new Backtrack[capacity];
 118         System.arraycopy (stack, 0, newStack, 0, size);
 119         stack = newStack;
 120       }
 121     stack[size++] = bt;
 122   }
 123
 124 }