1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 /* 19 * $Id$ 20 */ 21 package org.apache.xml.utils; 22 23 import java.util.EmptyStackException; 24 25 /** 26 * Implement a stack of simple integers. 27 * 28 * %OPT% 29 * This is currently based on ObjectVector, which permits fast acess but pays a 30 * heavy recopying penalty if/when its size is increased. If we expect deep 31 * stacks, we should consider a version based on ChunkedObjectVector. 32 * @xsl.usage internal 33 */ 34 public class ObjectStack extends ObjectVector 35 { 36 37 /** 38 * Default constructor. Note that the default 39 * block size is very small, for small lists. 40 */ ObjectStack()41 public ObjectStack() 42 { 43 super(); 44 } 45 46 /** 47 * Construct a ObjectVector, using the given block size. 48 * 49 * @param blocksize Size of block to allocate 50 */ ObjectStack(int blocksize)51 public ObjectStack(int blocksize) 52 { 53 super(blocksize); 54 } 55 56 /** 57 * Copy constructor for ObjectStack 58 * 59 * @param v ObjectStack to copy 60 */ ObjectStack(ObjectStack v)61 public ObjectStack (ObjectStack v) 62 { 63 super(v); 64 } 65 66 /** 67 * Pushes an item onto the top of this stack. 68 * 69 * @param i the int to be pushed onto this stack. 70 * @return the <code>item</code> argument. 71 */ push(Object i)72 public Object push(Object i) 73 { 74 75 if ((m_firstFree + 1) >= m_mapSize) 76 { 77 m_mapSize += m_blocksize; 78 79 Object newMap[] = new Object[m_mapSize]; 80 81 System.arraycopy(m_map, 0, newMap, 0, m_firstFree + 1); 82 83 m_map = newMap; 84 } 85 86 m_map[m_firstFree] = i; 87 88 m_firstFree++; 89 90 return i; 91 } 92 93 /** 94 * Removes the object at the top of this stack and returns that 95 * object as the value of this function. 96 * 97 * @return The object at the top of this stack. 98 */ pop()99 public Object pop() 100 { 101 Object val = m_map[--m_firstFree]; 102 m_map[m_firstFree] = null; 103 104 return val; 105 } 106 107 /** 108 * Quickly pops a number of items from the stack. 109 */ 110 quickPop(int n)111 public void quickPop(int n) 112 { 113 m_firstFree -= n; 114 } 115 116 /** 117 * Looks at the object at the top of this stack without removing it 118 * from the stack. 119 * 120 * @return the object at the top of this stack. 121 * @throws EmptyStackException if this stack is empty. 122 */ peek()123 public Object peek() 124 { 125 try { 126 return m_map[m_firstFree - 1]; 127 } 128 catch (ArrayIndexOutOfBoundsException e) 129 { 130 throw new EmptyStackException(); 131 } 132 } 133 134 /** 135 * Looks at the object at the position the stack counting down n items. 136 * 137 * @param n The number of items down, indexed from zero. 138 * @return the object at n items down. 139 * @throws EmptyStackException if this stack is empty. 140 */ peek(int n)141 public Object peek(int n) 142 { 143 try { 144 return m_map[m_firstFree-(1+n)]; 145 } 146 catch (ArrayIndexOutOfBoundsException e) 147 { 148 throw new EmptyStackException(); 149 } 150 } 151 152 /** 153 * Sets an object at a the top of the statck 154 * 155 * 156 * @param val object to set at the top 157 * @throws EmptyStackException if this stack is empty. 158 */ setTop(Object val)159 public void setTop(Object val) 160 { 161 try { 162 m_map[m_firstFree - 1] = val; 163 } 164 catch (ArrayIndexOutOfBoundsException e) 165 { 166 throw new EmptyStackException(); 167 } 168 } 169 170 /** 171 * Tests if this stack is empty. 172 * 173 * @return <code>true</code> if this stack is empty; 174 * <code>false</code> otherwise. 175 * @since JDK1.0 176 */ empty()177 public boolean empty() 178 { 179 return m_firstFree == 0; 180 } 181 182 /** 183 * Returns where an object is on this stack. 184 * 185 * @param o the desired object. 186 * @return the distance from the top of the stack where the object is] 187 * located; the return value <code>-1</code> indicates that the 188 * object is not on the stack. 189 * @since JDK1.0 190 */ search(Object o)191 public int search(Object o) 192 { 193 194 int i = lastIndexOf(o); 195 196 if (i >= 0) 197 { 198 return size() - i; 199 } 200 201 return -1; 202 } 203 204 /** 205 * Returns clone of current ObjectStack 206 * 207 * @return clone of current ObjectStack 208 */ clone()209 public Object clone() 210 throws CloneNotSupportedException 211 { 212 return (ObjectStack) super.clone(); 213 } 214 215 } 216