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1 <HTML>
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2 <HEAD>
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3 <TITLE>CLC-INTERCAL Reference</TITLE>
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4 </HEAD>
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5 <BODY>
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6 <H1>CLC-INTERCAL Reference</H1>
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7 <H2>... INTERcal NETworking</H2>
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8
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9 <P>
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10 Table of contents:
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11 <UL>
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12 <LI><A HREF="index.html">Parent directory</A>
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13 <LI><A HREF="#compiling">Compiling a program with INTERNET
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14 support</A>
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15 <LI><A HREF="#using">Using INTERNET</A>
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16 <LI><A HREF="#internals">Internals - or how you can interface
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17 to INTERNET enabled INTERCAL programs from other languages</A>
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18 </UL>
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19 </P>
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20
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21 <H2><A NAME="compiling">Compiling a program with INTERNET support</A></H2>
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22
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23 <P>
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24 Starting with CLC-INTERCAL 1.-94.-2, INTERNET is provided as a
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25 separate package, CLC-INTERCAL-INET. The rest of this chapter
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26 assumes that you have installed that package.
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27 </P>
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28
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29 <P>
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30 INTERNET is a standard compiler extension, so programs must include the
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31 appropriate compile option to use it.
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32 </P>
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33
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34 <P>
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35 The command-line compiler tool,
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36 <I>sick</I>, automatically enables the INTERNET extension if the program
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37 suffix includes the letter "r" (for remote - the letter "i"
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38 was already used to indicate that the program is an INTERCAL program).
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39 Alternatively, if you are not relying on <I>sick</I>'s guesses and
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40 are specifying a list of preloads yourself, just add <I>-pinternet</I>
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41 to your command line.
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42 </P>
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43
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44 <P>
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45 Using the INTERCAL Calculator, INTERCALC, you can easily add INTERNET
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46 support by selecting "internet" from the Options menu or by
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47 adding <I>-ointernet</I> to the command line.
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48 </P>
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49
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50 <P>
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51 The <I>internet</I> compiler object, which implements this extension,
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52 extends the compiler's syntax to include the STEAL, SMUGGLE and CASE
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53 statements; it also informs the runtime that the program should be
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54 listening for theft requests, and start a theft server if required:
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55 this is described below in the <A HREF="#internals">internals</A>
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56 section.
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57 </P>
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58
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59 <H2><A NAME="using">Using INTERNET</A></H2>
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60
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61 <P>
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62 Once you've enabled INTERNET support, using it is a simple matter of
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63 using STEAL, SMUGGLE or CASE statements as required; in this context,
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64 IGNORE and REMEMBER are also useful to allow/disallow access to
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65 your registers from other programs using STEAL and SMUGGLE. Details
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66 on these statements can be found in <A HREF="statements.html">the
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67 chapter about statements</A>.
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68 </P>
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69
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70 <P>
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71 Here is a simple example of an INTERNET program acting as a server:
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72 <PRE>
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73 DO IGNORE @1
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74 (1) PLEASE COME FROM (1)
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75 </PRE>
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76 It may seem rather pointless, but in fact this program will wait
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77 for network connections to SMUGGLE its standard write filehandle
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78 (normally stored in register @1). The filehandle can not be stolen,
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79 because it is ignored. The second statement is automatically caught
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80 by the runtime, which recognises an infinite loop when it sees one,
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81 and replaced with whatever is internally necessary to wait for a
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82 network connection: in other words, the busy wait specified by the
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83 COME FROM statement is replaced by an operating system specific
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84 wait for network connections, which does not consume any CPU until
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85 you try to SMUGGLE the standard write.
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86 </P>
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87
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88 <P>
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89 A client could do the following, after initialising the .1 register
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90 to contain the server's process ID, and the :1 register to contain
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91 the server's IP address:
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92 <PRE>
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93 DO SMUGGLE @1 ON .1 FROM :1
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94 DO WRITE IN .2
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95 </PRE>
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96 what happens here is that one line of input is obtained from the
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97 <I>server</I>'s standard read, and used in the <I>client</I> to
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98 assign a value to .2. The server and the client could be in completely
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99 different networks.
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100 </P>
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101
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102 <P>
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103 Note that this example would still work, once,
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104 if the server did not IGNORE @1 and the client used STEAL instead
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105 of SMUGGLE, however this would prevent a second client from using
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106 the same mechanism, because the server would no longer have the
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107 standard read filehandle available after the first client stole it.
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108 </P>
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109
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110 <P>
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111 We can develop this example a bit further. The server could use the
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112 system call interface to open a temporary file somewhere on the
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113 server, and make it available for smuggling to give other INTERCAL
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114 programs a chance to access the same file - even if they don't have
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115 access to the computer where the server runs. This program should
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116 be compiled with both the <I>internet</I> and <I>syscall</I>
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117 extensions, perhaps by giving it suffix <I>.rsi</I>:
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118 <PRE>
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119 PLEASE ,10 <- #18
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120 DO ,10 SUB #1 <- #95
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121 DO ,10 SUB #2 <- #91
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122 DO ,10 SUB #3 <- #93
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123 PLEASE ,10 SUB #4 <- #95
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124 DO ,10 SUB #5 <- #95
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125 DO ,10 SUB #6 <- #80
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126 DO ,10 SUB #7 <- #92
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127 PLEASE ,10 SUB #8 <- #86
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128 DO ,10 SUB #9 <- #91
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129 DO ,10 SUB #10 <- #93
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130 DO ,10 SUB #11 <- #95
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131 PLEASE ,10 SUB #12 <- #95
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132 DO ,10 SUB #13 <- #69
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133 DO ,10 SUB #14 <- #65
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134 DO ,10 SUB #15 <- #74
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135 PLEASE ,10 SUB #16 <- #94
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136 DO ,10 SUB #17 <- #65
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137 DO ,10 SUB #18 <- #74
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138 DO :10 <- #117
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139 (666) PLEASE .10 <- #3
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140 DO IGNORE @10
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141 (1) DO COME FROM (1)
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142 </PRE>
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143 The first part, from the start to the line with label (666),
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144 opens a file <CODE>/tmp/server</CODE> for reading and writing;
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145 the file name is stored in ,10 and the required access mode
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146 in :10, then system call #3 does the rest. The file will be
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147 associated with class variable @10. All the server has to do
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148 at this point is IGNORE @10 and wait for it to be smuggled.
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149 </P>
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150
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151 <P>
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152 A client could SMUGGLE @10 and just do normal file operations
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153 on it (using READ OUT, WRITE IN, and system call #4 and #5
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154 to perform seeks). Any changes made to the underlying file
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155 will be visible to other clients, as well as any user on the
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156 server computer who has access to the underlying file.
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157 The implementation of the client is left as an exercise to
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158 the reader.
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159 </P>
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160
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161 <H2><A NAME="internals">Internals</A></H2>
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162
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163 <P>
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164 This section will document the underlying protocol used to
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165 STEAL and SMUGGLE variables, as well as executing CASE statements;
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166 it will also show how programs written in other languages can
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167 communicate with INTERCAL programs using the INTERNET.
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168 </P>
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169
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170 <P>
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171 It's just unfortunate that this section hasn't been written yet.
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172 </P>
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173 </BODY>
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174 </HTML>
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175
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