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1 /*******************************************************************************
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2
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3 copyright: Copyright (c) 2004 Kris Bell. All rights reserved
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4
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5 license: BSD style: $(LICENSE)
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6
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7 version: July 2004: Initial release
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8
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9 author: Kris
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10
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11 *******************************************************************************/
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12
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13 module tango.net.cluster.tina.ProtocolReader;
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14
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15 private import tango.io.protocol.Reader,
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16 tango.io.protocol.Allocator,
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17 tango.io.protocol.PickleProtocol;
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18
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19 private import tango.net.cluster.model.IMessage;
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20
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21 private import tango.net.cluster.NetworkRegistry;
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22
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23 private import tango.net.cluster.tina.ClusterTypes;
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24
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25 /*******************************************************************************
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26
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27 Objects passed around a cluster are prefixed with a header, so the
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28 receiver can pick them apart correctly. This header consists of:
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29 ---
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30 * the packet size, including the header (16 bits)
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31 * a command code (8 bits)
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32 * a version id (8 bits)
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33 * a timestamp (64 bits)
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34 * length of the channel name (32 bits)
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35 * the channel name
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36 * length of the key (32 bits)
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37 * the key
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38 * an optional payload (an IMessage instance)
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39 ---
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40
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41 Everything is written in Network order (big endian).
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42
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43 *******************************************************************************/
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44
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45 class ProtocolReader : Reader
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46 {
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47 /***********************************************************************
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48
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49 Construct a ProtocolReader upon the given buffer. As
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50 Objects are serialized their content is written to this
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51 buffer. The buffer content is then typically flushed to
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52 some external conduit, such as a file or socket.
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53
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54 Note that arrays (such as text) are *always* sliced from
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55 the buffer -- there's no heap activity involved. Thus it
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56 may be necessary to .dup content where appropriate
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57
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58 ***********************************************************************/
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59
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60 this (IBuffer buffer)
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61 {
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62 super (new BufferSlice (new PickleProtocol (buffer)));
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63 }
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64
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65 /***********************************************************************
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66
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67 deserialize a payload into a provided host, or via
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68 the registered instance of the incoming payload
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69
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70 ***********************************************************************/
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71
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72 IMessage thaw (IMessage host = null)
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73 {
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74 return thaw (NetworkRegistry.shared, host);
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75 }
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76
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77 /***********************************************************************
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78
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79 deserialize a payload into a provided host, or via
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80 the registered instance of the incoming payload
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81
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82 ***********************************************************************/
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83
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84 IMessage thaw (NetworkRegistry registry, IMessage host = null)
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85 {
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86 return registry.thaw (this, host);
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87 }
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88
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89 /***********************************************************************
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90
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91 Read the protocol header and return true if there's a
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92 payload available
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93
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94 ***********************************************************************/
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95
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96 bool getHeader (inout ubyte cmd, inout char[] channel, inout char[] element)
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97 {
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98 auto position = buffer.position;
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99
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100 long time;
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101 ushort size;
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102 ubyte versn;
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103
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104 get (size) (cmd) (versn) (time);
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105
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106 // avoid allocation for these two strings
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107 get (channel) (element);
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108
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109 // is there a payload attached?
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110 if (size > (buffer.position - position))
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111 return true;
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112
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113 return false;
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114 }
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115
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116 /***********************************************************************
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117
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118 Return an aliased slice of the buffer representing the
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119 recieved payload. This is a bit of a hack, but eliminates
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120 a reasonable amount of overhead. Note that the channel/key
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121 text is retained right at the start of the returned content,
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122 enabling the host to toss the whole thing back without any
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123 further munging.
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124
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125 ***********************************************************************/
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126
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127 ClusterContent getPacket (inout ubyte cmd, inout char[] channel, inout char[] element, inout long time)
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128 {
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129 ushort size;
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130 ubyte versn;
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131
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132 // load up the header
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133 get (size) (cmd) (versn) (time);
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134
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135 //printf ("size: %d\n", cast(int) size);
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136
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137 // subtract header size
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138 size -= buffer.position;
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139
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140 // may throw an exception if the payload is too large to fit
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141 // completely inside the buffer!
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142 buffer.slice (size, false);
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143
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144 // slice the remaining packet (with channel/key text)
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145 auto content = cast(ClusterContent) buffer.slice;
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146
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147 // get a slice upon the channel name
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148 get (channel);
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149
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150 // get a slice upon the element name
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151 get (element);
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152
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153 // return the aliased payload (including channel/key text)
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154 return content;
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155 }
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156 }
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157
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