| 1 | package org.apache.velocity.util; |
| 2 | |
| 3 | /* |
| 4 | * Copyright 1999-2001,2004 The Apache Software Foundation. |
| 5 | * |
| 6 | * Licensed 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 | /** |
| 20 | * Simple object pool. Based on ThreadPool and few other classes |
| 21 | * |
| 22 | * The pool will ignore overflow and return null if empty. |
| 23 | * |
| 24 | * @author Gal Shachor |
| 25 | * @author Costin |
| 26 | * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> |
| 27 | * @version $Id: SimplePool.java,v 1.2.14.1 2004/03/03 23:23:07 geirm Exp $ |
| 28 | */ |
| 29 | public final class SimplePool |
| 30 | { |
| 31 | /* |
| 32 | * Where the objects are held. |
| 33 | */ |
| 34 | private Object pool[]; |
| 35 | |
| 36 | /** |
| 37 | * max amount of objects to be managed |
| 38 | * set via CTOR |
| 39 | */ |
| 40 | private int max; |
| 41 | |
| 42 | /** |
| 43 | * index of previous to next |
| 44 | * free slot |
| 45 | */ |
| 46 | private int current=-1; |
| 47 | |
| 48 | public SimplePool(int max) |
| 49 | { |
| 50 | this.max = max; |
| 51 | pool = new Object[max]; |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Add the object to the pool, silent nothing if the pool is full |
| 56 | */ |
| 57 | public void put(Object o) |
| 58 | { |
| 59 | int idx=-1; |
| 60 | |
| 61 | synchronized( this ) |
| 62 | { |
| 63 | /* |
| 64 | * if we aren't full |
| 65 | */ |
| 66 | |
| 67 | if( current < max - 1 ) |
| 68 | { |
| 69 | /* |
| 70 | * then increment the |
| 71 | * current index. |
| 72 | */ |
| 73 | idx = ++current; |
| 74 | } |
| 75 | |
| 76 | if( idx >= 0 ) |
| 77 | { |
| 78 | pool[idx] = o; |
| 79 | } |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Get an object from the pool, null if the pool is empty. |
| 85 | */ |
| 86 | public Object get() |
| 87 | { |
| 88 | int idx = -1; |
| 89 | |
| 90 | synchronized( this ) |
| 91 | { |
| 92 | /* |
| 93 | * if we have any in the pool |
| 94 | */ |
| 95 | if( current >= 0 ) |
| 96 | { |
| 97 | /* |
| 98 | * take one out, so to speak - |
| 99 | * separate the two operations |
| 100 | * to make it clear that you |
| 101 | * don't want idx = --current; :) |
| 102 | */ |
| 103 | |
| 104 | idx = current; |
| 105 | current--; |
| 106 | |
| 107 | /* |
| 108 | * and since current was >= 0 |
| 109 | * to get in here, idx must be as well |
| 110 | * so save the if() opration |
| 111 | */ |
| 112 | |
| 113 | return pool[idx]; |
| 114 | } |
| 115 | } |
| 116 | |
| 117 | return null; |
| 118 | } |
| 119 | |
| 120 | /** Return the size of the pool |
| 121 | */ |
| 122 | public int getMax() |
| 123 | { |
| 124 | return max; |
| 125 | } |
| 126 | } |