1*90c8c64dSAndroid Build Coastguard Worker /*
2*90c8c64dSAndroid Build Coastguard Worker  * Copyright (C) 2009 The Android Open Source Project
3*90c8c64dSAndroid Build Coastguard Worker  *
4*90c8c64dSAndroid Build Coastguard Worker  * Licensed under the Apache License, Version 2.0 (the "License");
5*90c8c64dSAndroid Build Coastguard Worker  * you may not use this file except in compliance with the License.
6*90c8c64dSAndroid Build Coastguard Worker  * You may obtain a copy of the License at
7*90c8c64dSAndroid Build Coastguard Worker  *
8*90c8c64dSAndroid Build Coastguard Worker  *      http://www.apache.org/licenses/LICENSE-2.0
9*90c8c64dSAndroid Build Coastguard Worker  *
10*90c8c64dSAndroid Build Coastguard Worker  * Unless required by applicable law or agreed to in writing, software
11*90c8c64dSAndroid Build Coastguard Worker  * distributed under the License is distributed on an "AS IS" BASIS,
12*90c8c64dSAndroid Build Coastguard Worker  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13*90c8c64dSAndroid Build Coastguard Worker  * See the License for the specific language governing permissions and
14*90c8c64dSAndroid Build Coastguard Worker  * limitations under the License.
15*90c8c64dSAndroid Build Coastguard Worker  */
16*90c8c64dSAndroid Build Coastguard Worker 
17*90c8c64dSAndroid Build Coastguard Worker package com.example.android.basicmultitouch;
18*90c8c64dSAndroid Build Coastguard Worker 
19*90c8c64dSAndroid Build Coastguard Worker /**
20*90c8c64dSAndroid Build Coastguard Worker  * Helper class for crating pools of objects. An example use looks like this:
21*90c8c64dSAndroid Build Coastguard Worker  * <pre>
22*90c8c64dSAndroid Build Coastguard Worker  * public class MyPooledClass {
23*90c8c64dSAndroid Build Coastguard Worker  *
24*90c8c64dSAndroid Build Coastguard Worker  *     private static final SynchronizedPool<MyPooledClass> sPool =
25*90c8c64dSAndroid Build Coastguard Worker  *             new SynchronizedPool<MyPooledClass>(10);
26*90c8c64dSAndroid Build Coastguard Worker  *
27*90c8c64dSAndroid Build Coastguard Worker  *     public static MyPooledClass obtain() {
28*90c8c64dSAndroid Build Coastguard Worker  *         MyPooledClass instance = sPool.acquire();
29*90c8c64dSAndroid Build Coastguard Worker  *         return (instance != null) ? instance : new MyPooledClass();
30*90c8c64dSAndroid Build Coastguard Worker  *     }
31*90c8c64dSAndroid Build Coastguard Worker  *
32*90c8c64dSAndroid Build Coastguard Worker  *     public void recycle() {
33*90c8c64dSAndroid Build Coastguard Worker  *          // Clear state if needed.
34*90c8c64dSAndroid Build Coastguard Worker  *          sPool.release(this);
35*90c8c64dSAndroid Build Coastguard Worker  *     }
36*90c8c64dSAndroid Build Coastguard Worker  *
37*90c8c64dSAndroid Build Coastguard Worker  *     . . .
38*90c8c64dSAndroid Build Coastguard Worker  * }
39*90c8c64dSAndroid Build Coastguard Worker  * </pre>
40*90c8c64dSAndroid Build Coastguard Worker  *
41*90c8c64dSAndroid Build Coastguard Worker  * @hide
42*90c8c64dSAndroid Build Coastguard Worker  */
43*90c8c64dSAndroid Build Coastguard Worker public final class Pools {
44*90c8c64dSAndroid Build Coastguard Worker 
45*90c8c64dSAndroid Build Coastguard Worker     /**
46*90c8c64dSAndroid Build Coastguard Worker      * Interface for managing a pool of objects.
47*90c8c64dSAndroid Build Coastguard Worker      *
48*90c8c64dSAndroid Build Coastguard Worker      * @param <T> The pooled type.
49*90c8c64dSAndroid Build Coastguard Worker      */
50*90c8c64dSAndroid Build Coastguard Worker     public static interface Pool<T> {
51*90c8c64dSAndroid Build Coastguard Worker 
52*90c8c64dSAndroid Build Coastguard Worker         /**
53*90c8c64dSAndroid Build Coastguard Worker          * @return An instance from the pool if such, null otherwise.
54*90c8c64dSAndroid Build Coastguard Worker          */
acquire()55*90c8c64dSAndroid Build Coastguard Worker         public T acquire();
56*90c8c64dSAndroid Build Coastguard Worker 
57*90c8c64dSAndroid Build Coastguard Worker         /**
58*90c8c64dSAndroid Build Coastguard Worker          * Release an instance to the pool.
59*90c8c64dSAndroid Build Coastguard Worker          *
60*90c8c64dSAndroid Build Coastguard Worker          * @param instance The instance to release.
61*90c8c64dSAndroid Build Coastguard Worker          * @return Whether the instance was put in the pool.
62*90c8c64dSAndroid Build Coastguard Worker          *
63*90c8c64dSAndroid Build Coastguard Worker          * @throws IllegalStateException If the instance is already in the pool.
64*90c8c64dSAndroid Build Coastguard Worker          */
release(T instance)65*90c8c64dSAndroid Build Coastguard Worker         public boolean release(T instance);
66*90c8c64dSAndroid Build Coastguard Worker     }
67*90c8c64dSAndroid Build Coastguard Worker 
Pools()68*90c8c64dSAndroid Build Coastguard Worker     private Pools() {
69*90c8c64dSAndroid Build Coastguard Worker         /* do nothing - hiding constructor */
70*90c8c64dSAndroid Build Coastguard Worker     }
71*90c8c64dSAndroid Build Coastguard Worker 
72*90c8c64dSAndroid Build Coastguard Worker     /**
73*90c8c64dSAndroid Build Coastguard Worker      * Simple (non-synchronized) pool of objects.
74*90c8c64dSAndroid Build Coastguard Worker      *
75*90c8c64dSAndroid Build Coastguard Worker      * @param <T> The pooled type.
76*90c8c64dSAndroid Build Coastguard Worker      */
77*90c8c64dSAndroid Build Coastguard Worker     public static class SimplePool<T> implements Pool<T> {
78*90c8c64dSAndroid Build Coastguard Worker         private final Object[] mPool;
79*90c8c64dSAndroid Build Coastguard Worker 
80*90c8c64dSAndroid Build Coastguard Worker         private int mPoolSize;
81*90c8c64dSAndroid Build Coastguard Worker 
82*90c8c64dSAndroid Build Coastguard Worker         /**
83*90c8c64dSAndroid Build Coastguard Worker          * Creates a new instance.
84*90c8c64dSAndroid Build Coastguard Worker          *
85*90c8c64dSAndroid Build Coastguard Worker          * @param maxPoolSize The max pool size.
86*90c8c64dSAndroid Build Coastguard Worker          *
87*90c8c64dSAndroid Build Coastguard Worker          * @throws IllegalArgumentException If the max pool size is less than zero.
88*90c8c64dSAndroid Build Coastguard Worker          */
SimplePool(int maxPoolSize)89*90c8c64dSAndroid Build Coastguard Worker         public SimplePool(int maxPoolSize) {
90*90c8c64dSAndroid Build Coastguard Worker             if (maxPoolSize <= 0) {
91*90c8c64dSAndroid Build Coastguard Worker                 throw new IllegalArgumentException("The max pool size must be > 0");
92*90c8c64dSAndroid Build Coastguard Worker             }
93*90c8c64dSAndroid Build Coastguard Worker             mPool = new Object[maxPoolSize];
94*90c8c64dSAndroid Build Coastguard Worker         }
95*90c8c64dSAndroid Build Coastguard Worker 
96*90c8c64dSAndroid Build Coastguard Worker         @Override
97*90c8c64dSAndroid Build Coastguard Worker         @SuppressWarnings("unchecked")
acquire()98*90c8c64dSAndroid Build Coastguard Worker         public T acquire() {
99*90c8c64dSAndroid Build Coastguard Worker             if (mPoolSize > 0) {
100*90c8c64dSAndroid Build Coastguard Worker                 final int lastPooledIndex = mPoolSize - 1;
101*90c8c64dSAndroid Build Coastguard Worker                 T instance = (T) mPool[lastPooledIndex];
102*90c8c64dSAndroid Build Coastguard Worker                 mPool[lastPooledIndex] = null;
103*90c8c64dSAndroid Build Coastguard Worker                 mPoolSize--;
104*90c8c64dSAndroid Build Coastguard Worker                 return instance;
105*90c8c64dSAndroid Build Coastguard Worker             }
106*90c8c64dSAndroid Build Coastguard Worker             return null;
107*90c8c64dSAndroid Build Coastguard Worker         }
108*90c8c64dSAndroid Build Coastguard Worker 
109*90c8c64dSAndroid Build Coastguard Worker         @Override
release(T instance)110*90c8c64dSAndroid Build Coastguard Worker         public boolean release(T instance) {
111*90c8c64dSAndroid Build Coastguard Worker             if (isInPool(instance)) {
112*90c8c64dSAndroid Build Coastguard Worker                 throw new IllegalStateException("Already in the pool!");
113*90c8c64dSAndroid Build Coastguard Worker             }
114*90c8c64dSAndroid Build Coastguard Worker             if (mPoolSize < mPool.length) {
115*90c8c64dSAndroid Build Coastguard Worker                 mPool[mPoolSize] = instance;
116*90c8c64dSAndroid Build Coastguard Worker                 mPoolSize++;
117*90c8c64dSAndroid Build Coastguard Worker                 return true;
118*90c8c64dSAndroid Build Coastguard Worker             }
119*90c8c64dSAndroid Build Coastguard Worker             return false;
120*90c8c64dSAndroid Build Coastguard Worker         }
121*90c8c64dSAndroid Build Coastguard Worker 
isInPool(T instance)122*90c8c64dSAndroid Build Coastguard Worker         private boolean isInPool(T instance) {
123*90c8c64dSAndroid Build Coastguard Worker             for (int i = 0; i < mPoolSize; i++) {
124*90c8c64dSAndroid Build Coastguard Worker                 if (mPool[i] == instance) {
125*90c8c64dSAndroid Build Coastguard Worker                     return true;
126*90c8c64dSAndroid Build Coastguard Worker                 }
127*90c8c64dSAndroid Build Coastguard Worker             }
128*90c8c64dSAndroid Build Coastguard Worker             return false;
129*90c8c64dSAndroid Build Coastguard Worker         }
130*90c8c64dSAndroid Build Coastguard Worker     }
131*90c8c64dSAndroid Build Coastguard Worker 
132*90c8c64dSAndroid Build Coastguard Worker     /**
133*90c8c64dSAndroid Build Coastguard Worker      * Synchronized) pool of objects.
134*90c8c64dSAndroid Build Coastguard Worker      *
135*90c8c64dSAndroid Build Coastguard Worker      * @param <T> The pooled type.
136*90c8c64dSAndroid Build Coastguard Worker      */
137*90c8c64dSAndroid Build Coastguard Worker     public static class SynchronizedPool<T> extends SimplePool<T> {
138*90c8c64dSAndroid Build Coastguard Worker         private final Object mLock = new Object();
139*90c8c64dSAndroid Build Coastguard Worker 
140*90c8c64dSAndroid Build Coastguard Worker         /**
141*90c8c64dSAndroid Build Coastguard Worker          * Creates a new instance.
142*90c8c64dSAndroid Build Coastguard Worker          *
143*90c8c64dSAndroid Build Coastguard Worker          * @param maxPoolSize The max pool size.
144*90c8c64dSAndroid Build Coastguard Worker          *
145*90c8c64dSAndroid Build Coastguard Worker          * @throws IllegalArgumentException If the max pool size is less than zero.
146*90c8c64dSAndroid Build Coastguard Worker          */
SynchronizedPool(int maxPoolSize)147*90c8c64dSAndroid Build Coastguard Worker         public SynchronizedPool(int maxPoolSize) {
148*90c8c64dSAndroid Build Coastguard Worker             super(maxPoolSize);
149*90c8c64dSAndroid Build Coastguard Worker         }
150*90c8c64dSAndroid Build Coastguard Worker 
151*90c8c64dSAndroid Build Coastguard Worker         @Override
acquire()152*90c8c64dSAndroid Build Coastguard Worker         public T acquire() {
153*90c8c64dSAndroid Build Coastguard Worker             synchronized (mLock) {
154*90c8c64dSAndroid Build Coastguard Worker                 return super.acquire();
155*90c8c64dSAndroid Build Coastguard Worker             }
156*90c8c64dSAndroid Build Coastguard Worker         }
157*90c8c64dSAndroid Build Coastguard Worker 
158*90c8c64dSAndroid Build Coastguard Worker         @Override
release(T element)159*90c8c64dSAndroid Build Coastguard Worker         public boolean release(T element) {
160*90c8c64dSAndroid Build Coastguard Worker             synchronized (mLock) {
161*90c8c64dSAndroid Build Coastguard Worker                 return super.release(element);
162*90c8c64dSAndroid Build Coastguard Worker             }
163*90c8c64dSAndroid Build Coastguard Worker         }
164*90c8c64dSAndroid Build Coastguard Worker     }
165*90c8c64dSAndroid Build Coastguard Worker }
166