Source Code Cross Referenced for ImmortalContext.java in  » Science » javolution-5.2 » javolution » context » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Science » javolution 5.2 » javolution.context 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Javolution - Java(TM) Solution for Real-Time and Embedded Systems
003:         * Copyright (C) 2007 - Javolution (http://javolution.org/)
004:         * All rights reserved.
005:         * 
006:         * Permission to use, copy, modify, and distribute this software is
007:         * freely granted, provided that this notice is preserved.
008:         */
009:        package javolution.context;
010:
011:        import j2me.lang.ThreadLocal;
012:        import j2mex.realtime.MemoryArea;
013:        import javolution.util.FastMap;
014:        import javolution.util.FastTable;
015:
016:        /**
017:         * <p> This class represents an allocator from immortal memory (RTSJ).</p>
018:         * 
019:         * <p> It is typically used to allocate (and recycle) from immortal memory
020:         *     allowing dynamically created static instances to be accessible by 
021:         *     <code>NoHeapRealtimeThread</code>:[code] 
022:         *         public synchronized Text intern() {
023:         *             if (!INTERN_INSTANCES.containsKey(this)) {
024:         *                 ImmortalContext.enter(); 
025:         *                 try { // Forces interned instance to be in immortal memory.
026:         *                     Text txt = this.copy(); // In ImmortalMemory.
027:         *                     INTERN_INSTANCES.put(txt, txt);
028:         *                 } finally {
029:         *                     ImmortalContext.exit();
030:         *                 }
031:         *             }
032:         *             return (Text) INTERN_INSTANCES.get(str);
033:         *         }[/code]</p>
034:         * <p> Because class initialization may occur while running in a non-heap
035:         *     context (e.g. {@link StackContext}), it is recommended to force 
036:         *     factory produced constants to immortal memory:[code]         
037:         *         public class Rational {
038:         *             public static final Rational ZERO;
039:         *             public static final Rational ONE;
040:         *             ...
041:         *             static { // Forces constants to ImmortalMemory.
042:         *                 ImmortalContext.enter();
043:         *                 try {
044:         *                     ZERO = Rational.valueOf(0, 1); // Factory produced.
045:         *                     ONE = Rational.valueOf(1, 1); // Factory produced.
046:         *                 } finally {
047:         *                     ImmortalContext.exit();
048:         *                 } 
049:         *             }
050:         *        }[/code]</p>
051:         *        
052:         * @author  <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
053:         * @version 5.2, August 19, 2007
054:         */
055:        public final class ImmortalContext extends AllocatorContext {
056:
057:            /**
058:             * Holds the class.
059:             */
060:            private static final Class CLASS = new ImmortalContext().getClass();
061:
062:            /**
063:             * Holds the factory to allocator mapping (per thread).
064:             */
065:            private static final ThreadLocal FACTORY_TO_ALLOCATOR = new ThreadLocal() {
066:                protected Object initialValue() {
067:                    return new FastMap();
068:                }
069:            };
070:
071:            /**
072:             * Holds the allocators which have been activated (per thread).
073:             */
074:            private static final ThreadLocal ACTIVE_ALLOCATORS = new ThreadLocal() {
075:                protected Object initialValue() {
076:                    return new FastTable();
077:                }
078:            };
079:
080:            /**
081:             * Enters an immortal memory context.
082:             * 
083:             * @return the immortal memory context entered.
084:             */
085:            public static ImmortalContext enter() {
086:                return (ImmortalContext) Context.enter(ImmortalContext.CLASS);
087:            }
088:
089:            /**
090:             * Exits the current immortal memory context.
091:             * 
092:             * @return the immortal context being exited.
093:             * @throws ClassCastException if the context is not an immortal context.
094:             */
095:            public static/*ImmortalContext*/Context exit() {
096:                return (ImmortalContext) Context.exit();
097:            }
098:
099:            /**
100:             * Default constructor (private, instances are factory produced).
101:             */
102:            private ImmortalContext() {
103:            }
104:
105:            // Overrides.
106:            protected void deactivate() {
107:                FastTable allocators = (FastTable) ACTIVE_ALLOCATORS.get();
108:                for (int i = 0, n = allocators.size(); i < n;) {
109:                    ((Allocator) allocators.get(i++)).user = null;
110:                }
111:                allocators.clear();
112:            }
113:
114:            // Overrides.
115:            protected Allocator getAllocator(ObjectFactory factory) {
116:                final FastMap factoryToAllocator = (FastMap) FACTORY_TO_ALLOCATOR
117:                        .get();
118:                ImmortalAllocator allocator = (ImmortalAllocator) factoryToAllocator
119:                        .get(factory);
120:                if (allocator == null) {
121:                    allocator = new ImmortalAllocator(factory);
122:                    factoryToAllocator.put(factory, allocator);
123:                }
124:                if (allocator.user == null) { // Activate.
125:                    allocator.user = Thread.currentThread();
126:                    FastTable activeAllocators = (FastTable) ACTIVE_ALLOCATORS
127:                            .get();
128:                    activeAllocators.add(allocator);
129:                }
130:                return allocator;
131:            }
132:
133:            // Overrides.
134:            protected void enterAction() {
135:                getOuter().getAllocatorContext().deactivate();
136:            }
137:
138:            // Overrides.
139:            protected void exitAction() {
140:                this .deactivate();
141:            }
142:
143:            // Holds immortal allocator implementation.
144:            private static final class ImmortalAllocator extends Allocator {
145:
146:                private static final MemoryArea IMMORTAL = MemoryArea
147:                        .getMemoryArea("");
148:
149:                private final ObjectFactory _factory;
150:
151:                private Object _allocated;
152:
153:                public ImmortalAllocator(ObjectFactory factory) {
154:                    _factory = factory;
155:                }
156:
157:                private final Runnable _allocate = new Runnable() {
158:                    public void run() {
159:                        _allocated = _factory.create();
160:                    }
161:                };
162:
163:                private final Runnable _resize = new Runnable() {
164:                    public void run() {
165:                        resize();
166:                    }
167:                };
168:
169:                protected Object allocate() {
170:                    IMMORTAL.executeInArea(_allocate);
171:                    return _allocated;
172:                }
173:
174:                protected void recycle(Object object) {
175:                    if (_factory.doCleanup()) {
176:                        _factory.cleanup(object);
177:                    }
178:                    if (queueSize >= queue.length) {
179:                        IMMORTAL.executeInArea(_resize);
180:                    }
181:                    queue[queueSize++] = object;
182:                }
183:
184:                public String toString() {
185:                    return "Immortal allocator for " + _factory.getClass();
186:                }
187:            }
188:
189:            // Allows instances to be factory produced (private constructor). 
190:            static {
191:                ObjectFactory.setInstance(new ObjectFactory() {
192:                    protected Object create() {
193:                        return new ImmortalContext();
194:                    }
195:                }, ImmortalContext.CLASS);
196:            }
197:        }
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