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1 package suikwasha.distributedalgorithm.algorithms.peterson;
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2
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3 import java.nio.ByteBuffer;
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4 import java.util.Iterator;
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5
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6 import suikwasha.distributedalgorithm.framework.Algorithm;
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7 import suikwasha.distributedalgorithm.framework.Context;
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8 import suikwasha.distributedalgorithm.framework.Message;
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9 import suikwasha.distributedalgorithm.framework.Port;
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10
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11 public class PertersonAlgorithm implements Algorithm
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12 {
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13 private final long num;
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14 private long max;
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15
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16 public PertersonAlgorithm(long _num)
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17 {
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18 max = -1;
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19 num = _num;
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20 }
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21
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22 public static ByteBuffer toByteBuffer(boolean _max,long _value)
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23 {
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24 ByteBuffer b = ByteBuffer.allocate(9); // size of (flag + long)
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25 if(_max){
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26 b.put((byte)1);
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27 }else{
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28 b.put((byte)0);
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29 }
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30
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31 b.putLong(_value);
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32 b.rewind(); // do not forget rewind() after reading/writing
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33 return b.asReadOnlyBuffer(); // message is read-only
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34 }
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35
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36 public void execute(Context _c)
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37 {
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38 Iterator<Port> ports = _c.getPorts().iterator();
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39 Port in = ports.next();
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40 Port out = ports.next();
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41
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42 /*
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43 * Active
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44 */
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45
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46 long temp = num;
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47 out.send(new Message(toByteBuffer(false,temp)));
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48
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49 Message receivedMessage = null;
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50 try{
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51 receivedMessage = in.blockingReceive();
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52 }catch(InterruptedException _e){
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53 _e.printStackTrace();
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54 }
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55
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56 ByteBuffer b = receivedMessage.getMessage();
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57 long next = -1;
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58 if(b.get() == (byte)0){
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59 next = b.getLong();
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60 }else{
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61 System.out.println("b.get() != 0");
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62 }
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63
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64 Message newMessage;
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65 while(temp != next){
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66 newMessage = receivedMessage.newMessage(toByteBuffer(false,next));
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67 out.send(newMessage);
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68 try{
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69 receivedMessage = in.blockingReceive();
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70 }catch(InterruptedException _e){
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71 _e.printStackTrace();
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72 }
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73 long nnext = -1;
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74 b = receivedMessage.getMessage();
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75 if(b.get() == (byte)0){
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76 nnext = b.getLong();
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77 }
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78 if(next < Math.max(temp,nnext)){
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79 break;
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80 }
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81 if(next > Math.max(temp,nnext)){
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82 temp = next;
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83 }
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84 newMessage = receivedMessage.newMessage(toByteBuffer(false,temp));
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85 out.send(newMessage);
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86 newMessage = receivedMessage.newMessage(toByteBuffer(false,next));
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87 out.send(newMessage);
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88 }
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89
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90 if(temp == next){
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91 max = temp;
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92 newMessage = receivedMessage.newMessage(toByteBuffer(true,max));
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93 out.send(newMessage);
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94
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95 // stop
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96 return;
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97 }
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98
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99 /*
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100 * Passive
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101 */
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102 while(true){
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103 try{
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104 receivedMessage = in.blockingReceive();
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105 }catch(InterruptedException _e){
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106 _e.printStackTrace();
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107 }
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108 b = receivedMessage.getMessage();
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109 if(b.get() == (byte)1){
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110 max = b.getLong();
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111 newMessage = receivedMessage.newMessage(toByteBuffer(true,max));
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112 out.send(newMessage);
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113
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114 //stop
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115 return;
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116 }
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117
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118 long value = b.getLong();
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119 newMessage = receivedMessage.newMessage(toByteBuffer(false,value));
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120 out.send(newMessage);
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121 }
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122 }
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123 }
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