| 1 | /******************************************************************************
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| 2 | *
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| 3 | * Copyright (c) 2000 by Mindbright Technology AB, Stockholm, Sweden.
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| 4 | * www.mindbright.se, [email protected]
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| 5 | *
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| 6 | * This program is free software; you can redistribute it and/or modify
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| 7 | * it under the terms of the GNU General Public License as published by
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| 8 | * the Free Software Foundation; either version 2 of the License, or
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| 9 | * (at your option) any later version.
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| 10 | *
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| 11 | * This program is distributed in the hope that it will be useful,
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| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 14 | * GNU General Public License for more details.
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| 15 | *
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| 16 | *****************************************************************************
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| 17 | * $Author: mats $
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| 18 | * $Date: 2000/05/29 10:54:03 $
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| 19 | * $Name: rel1-2-1 $
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| 20 | *****************************************************************************/
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| 21 | package mindbright.util;
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| 22 |
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| 23 | public final class Queue {
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| 24 |
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| 25 | final static int QUEUE_DEPTH = 512;
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| 26 | final static int QUEUE_HIWATER = 384;
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| 27 |
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| 28 | Object[] queue;
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| 29 | boolean isWaitGet;
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| 30 | boolean isWaitPut;
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| 31 | boolean isBlocking;
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| 32 | int rOffset;
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| 33 | int wOffset;
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| 34 | int maxQueueDepth;
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| 35 |
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| 36 | // Copies used for saving real values when disabling queue
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| 37 | //
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| 38 | int rOffsetCP;
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| 39 | int wOffsetCP;
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| 40 | int maxQueueDepthCP;
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| 41 |
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| 42 | public Queue() {
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| 43 | this.queue = new Object[QUEUE_DEPTH + 1];
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| 44 | this.isWaitGet = false;
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| 45 | this.isWaitPut = false;
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| 46 | this.isBlocking = true;
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| 47 | this.rOffset = 0;
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| 48 | this.wOffset = 0;
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| 49 | this.maxQueueDepth = QUEUE_DEPTH;
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| 50 | }
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| 51 |
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| 52 | public synchronized void setMaxDepth(int maxDepth) {
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| 53 | maxQueueDepth = maxDepth;
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| 54 | }
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| 55 |
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| 56 | public synchronized void putLast(Object obj) {
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| 57 | putFlowControl();
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| 58 | queue[wOffset++] = obj;
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| 59 | if(wOffset == (QUEUE_DEPTH + 1))
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| 60 | wOffset = 0;
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| 61 | if(isWaitGet)
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| 62 | this.notify();
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| 63 | }
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| 64 |
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| 65 | public synchronized void putFirst(Object obj) {
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| 66 | putFlowControl();
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| 67 | rOffset--;
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| 68 | if(rOffset == -1)
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| 69 | rOffset = QUEUE_DEPTH;
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| 70 | queue[rOffset] = obj;
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| 71 | if(isWaitGet)
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| 72 | this.notify();
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| 73 | }
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| 74 |
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| 75 | public synchronized void release() {
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| 76 | if(isWaitGet)
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| 77 | this.notify();
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| 78 | }
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| 79 |
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| 80 | public synchronized void disable() {
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| 81 | rOffsetCP = rOffset;
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| 82 | wOffsetCP = wOffset;
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| 83 | maxQueueDepthCP = maxQueueDepth;
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| 84 | rOffset = 0;
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| 85 | wOffset = 0;
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| 86 | maxQueueDepth = 0;
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| 87 | }
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| 88 |
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| 89 | public synchronized void enable() {
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| 90 | rOffset = rOffsetCP;
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| 91 | wOffset = wOffsetCP;
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| 92 | maxQueueDepth = maxQueueDepthCP;
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| 93 | if(!isEmpty()) {
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| 94 | this.release();
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| 95 | }
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| 96 | if(isWaitPut && (freeSpace() > (QUEUE_DEPTH - QUEUE_HIWATER))) {
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| 97 | this.notifyAll();
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| 98 | isWaitPut = false;
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| 99 | }
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| 100 | }
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| 101 |
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| 102 | public synchronized void setBlocking(boolean block) {
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| 103 | isBlocking = block;
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| 104 | release();
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| 105 | }
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| 106 |
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| 107 | public synchronized boolean isEmpty() {
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| 108 | return (rOffset == wOffset);
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| 109 | }
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| 110 |
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| 111 | private final void putFlowControl() {
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| 112 | int fs = freeSpace();
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| 113 | if(fs == (QUEUE_DEPTH - maxQueueDepth)) {
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| 114 | isWaitPut = true;
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| 115 | }
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| 116 | if(isWaitPut) {
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| 117 | try {
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| 118 | this.wait();
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| 119 | } catch (InterruptedException e) {
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| 120 | // !!!
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| 121 | }
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| 122 | }
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| 123 | }
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| 124 |
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| 125 | private final int freeSpace() {
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| 126 | int fSpc = rOffset - wOffset;
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| 127 | if(fSpc <= 0)
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| 128 | fSpc += (QUEUE_DEPTH + 1);
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| 129 | fSpc--;
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| 130 | return fSpc;
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| 131 | }
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| 132 |
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| 133 | public synchronized Object getFirst() {
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| 134 | Object obj = null;
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| 135 | if(isEmpty()) {
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| 136 | if(!isBlocking) {
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| 137 | return null;
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| 138 | }
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| 139 | isWaitGet = true;
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| 140 | try {
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| 141 | this.wait();
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| 142 | } catch (InterruptedException e) {
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| 143 | // !!!
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| 144 | }
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| 145 | }
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| 146 | isWaitGet = false;
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| 147 | obj = queue[rOffset];
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| 148 | queue[rOffset++] = null;
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| 149 | if(rOffset == (QUEUE_DEPTH + 1))
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| 150 | rOffset = 0;
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| 151 | if(isWaitPut && (freeSpace() > (QUEUE_DEPTH - QUEUE_HIWATER))) {
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| 152 | this.notifyAll();
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| 153 | isWaitPut = false;
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| 154 | }
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| 155 | return obj;
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| 156 | }
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| 157 | }
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