| 1 | /******************************************************************************
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| 2 | *
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| 3 | * Copyright (c) 1998,99 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: 2000/03/14 18:38:19 $
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| 19 | * $Name: rel1-2-1 $
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| 20 | *****************************************************************************/
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| 21 | package mindbright.ssh;
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| 22 |
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| 23 | public final class SSHPduQueue {
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| 24 |
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| 25 | final static int SSH_QUEUE_DEPTH = 512;
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| 26 | final static int SSH_QUEUE_HIWATER = 384;
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| 27 |
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| 28 | Object[] queue;
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| 29 | Object queueLock;
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| 30 | boolean isWaitGet;
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| 31 | boolean isWaitPut;
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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 | public SSHPduQueue() {
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| 37 | this.queue = new Object[SSH_QUEUE_DEPTH + 1];
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| 38 | this.queueLock = new Object();
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| 39 | this.isWaitGet = false;
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| 40 | this.isWaitPut = false;
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| 41 | this.rOffset = 0;
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| 42 | this.wOffset = 0;
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| 43 | this.maxQueueDepth = SSH_QUEUE_DEPTH;
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| 44 | }
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| 45 |
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| 46 | public void setMaxDepth(int maxDepth) {
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| 47 | synchronized(queueLock) {
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| 48 | maxQueueDepth = maxDepth;
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| 49 | }
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| 50 | }
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| 51 |
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| 52 | public void putLast(SSHPdu pdu) {
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| 53 | synchronized(queueLock) {
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| 54 | putFlowControl();
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| 55 | queue[wOffset++] = pdu;
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| 56 | if(wOffset == (SSH_QUEUE_DEPTH + 1))
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| 57 | wOffset = 0;
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| 58 | if(isWaitGet)
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| 59 | queueLock.notify();
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| 60 | }
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| 61 | }
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| 62 |
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| 63 | public void putFirst(SSHPdu pdu) {
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| 64 | synchronized(queueLock) {
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| 65 | putFlowControl();
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| 66 | rOffset--;
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| 67 | if(rOffset == -1)
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| 68 | rOffset = SSH_QUEUE_DEPTH;
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| 69 | queue[rOffset] = pdu;
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| 70 | if(isWaitGet)
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| 71 | queueLock.notify();
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| 72 | }
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| 73 | }
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| 74 |
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| 75 | public void release() {
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| 76 | synchronized(queueLock) {
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| 77 | if(isWaitGet)
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| 78 | queueLock.notify();
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| 79 | }
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| 80 | }
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| 81 |
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| 82 | public boolean isEmpty() {
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| 83 | boolean isEmpty;
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| 84 | synchronized(queueLock) {
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| 85 | isEmpty = (rOffset == wOffset);
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| 86 | }
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| 87 | return isEmpty;
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| 88 | }
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| 89 |
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| 90 | private final void putFlowControl() {
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| 91 | int fs = freeSpace();
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| 92 | if(fs == (SSH_QUEUE_DEPTH - maxQueueDepth)) {
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| 93 | isWaitPut = true;
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| 94 | }
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| 95 | if(isWaitPut) {
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| 96 | try {
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| 97 | queueLock.wait();
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| 98 | } catch (InterruptedException e) {
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| 99 | // !!!
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| 100 | }
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| 101 | }
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| 102 | }
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| 103 |
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| 104 | private final int freeSpace() {
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| 105 | int fSpc = rOffset - wOffset;
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| 106 | if(fSpc <= 0)
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| 107 | fSpc += (SSH_QUEUE_DEPTH + 1);
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| 108 | fSpc--;
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| 109 | return fSpc;
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| 110 | }
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| 111 |
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| 112 | public SSHPdu getFirst() {
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| 113 | SSHPdu pdu = null;
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| 114 |
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| 115 | synchronized(queueLock) {
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| 116 | if(isEmpty()) {
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| 117 | isWaitGet = true;
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| 118 | try {
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| 119 | queueLock.wait();
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| 120 | } catch (InterruptedException e) {
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| 121 | // !!!
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| 122 | }
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| 123 | }
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| 124 | isWaitGet = false;
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| 125 | pdu = (SSHPdu) queue[rOffset];
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| 126 | queue[rOffset++] = null;
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| 127 | if(rOffset == (SSH_QUEUE_DEPTH + 1))
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| 128 | rOffset = 0;
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| 129 | if(isWaitPut && (freeSpace() > (SSH_QUEUE_DEPTH - SSH_QUEUE_HIWATER))) {
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| 130 | queueLock.notifyAll();
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| 131 | isWaitPut = false;
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| 132 | }
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| 133 | }
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| 134 |
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| 135 | return pdu;
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| 136 | }
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| 137 |
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| 138 | }
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