001: /*
002: *
003: *
004: * Copyright 1990-2007 Sun Microsystems, Inc. All Rights Reserved.
005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
006: *
007: * This program is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU General Public License version
009: * 2 only, as published by the Free Software Foundation.
010: *
011: * This program is distributed in the hope that it will be useful, but
012: * WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014: * General Public License version 2 for more details (a copy is
015: * included at /legal/license.txt).
016: *
017: * You should have received a copy of the GNU General Public License
018: * version 2 along with this work; if not, write to the Free Software
019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020: * 02110-1301 USA
021: *
022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
023: * Clara, CA 95054 or visit www.sun.com if you need additional
024: * information or have any questions.
025: */
026:
027: package com.sun.midp.automation;
028:
029: /**
030: * Utility class for tracking states
031: */
032: class AutoStateTracker {
033: /**
034: * Protected by 'this' lock
035: */
036:
037: /** Current state */
038: private Object currentState;
039:
040: /** Number of waiters currently waiting */
041: private int totalWaiters;
042:
043: /** flag, indicating that wait must be interrupted */
044: private boolean interruptWait;
045:
046: /**
047: * Protected by wakeWaitersLock
048: */
049:
050: /** Lock used to wait for waiters to awake */
051: private Object wakeWaitersLock;
052:
053: /** Number of waiters to awake */
054: private int waitersToWake;
055:
056: /**
057: * Constructor
058: *
059: * @param initialState initial state
060: */
061: AutoStateTracker(Object initialState) {
062: currentState = initialState;
063: totalWaiters = 0;
064: waitersToWake = 0;
065: interruptWait = false;
066: wakeWaitersLock = new Object();
067: }
068:
069: /**
070: * Returns current state.
071: *
072: * @return current state
073: */
074: final Object getCurrentState() {
075: synchronized (this ) {
076: return currentState;
077: }
078: }
079:
080: /**
081: * Sets a state.
082: * Assumption: only one thread sets a state,
083: * 'this' lock shouldn't be already taken.
084: *
085: * @param state state to set as current
086: * @param interrupt if true, interrupt all waiters
087: * after setting a state.
088: */
089: final void setCurrentState(Object state, boolean interrupt) {
090: synchronized (this ) {
091: if (currentState == state) {
092: return;
093: }
094:
095: interruptWait = interrupt;
096: currentState = state;
097: waitersToWake = totalWaiters;
098: notifyAll();
099: }
100:
101: // wait until all waiters have been awaken, so they have
102: // a chance to recheck condition they are waiting for
103: synchronized (wakeWaitersLock) {
104: while (waitersToWake != 0) {
105: try {
106: wakeWaitersLock.wait();
107: } catch (InterruptedException e) {
108: // just ignore
109: }
110: }
111: }
112: }
113:
114: /**
115: * Interrupts waiters
116: */
117: final void interruptWait() {
118: synchronized (this ) {
119: interruptWait = true;
120: notifyAll();
121: }
122: }
123:
124: /**
125: * Checks condition waiters are waiting for:
126: * specified state has been reached.
127: * Assumption: 'this' lock is already taken.
128: *
129: * @param state state to check againts
130: * @return true, if specified state has been reached
131: */
132: protected boolean isStateReached(Object state) {
133: return (currentState == state);
134: }
135:
136: /**
137: * Waits until specified state has been reached.
138: *
139: * @param state state to wait for
140: */
141: final void waitFor(Object state) {
142: synchronized (this ) {
143: while (!isStateReached(state) && !interruptWait) {
144: try {
145: totalWaiters++;
146: wait();
147: totalWaiters--;
148:
149: synchronized (wakeWaitersLock) {
150: waitersToWake--;
151: // if all threads affected by setCurrentState
152: // notification have waken up, notify setCurrentState
153: // about it
154: if (waitersToWake == 0) {
155: wakeWaitersLock.notify();
156: }
157: }
158: } catch (InterruptedException e) {
159: // just ignore
160: }
161: }
162: }
163: }
164: }
|