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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+  <header>
+    <copyright>
+      <year>1998</year><year>2009</year>
+      <holder>Ericsson AB. All Rights Reserved.</holder>
+    </copyright>
+    <legalnotice>
+      The contents of this file are subject to the Erlang Public License,
+      Version 1.1, (the "License"); you may not use this file except in
+      compliance with the License. You should have received a copy of the
+      Erlang Public License along with this software. If not, it can be
+      retrieved online at http://www.erlang.org/.
+    
+      Software distributed under the License is distributed on an "AS IS"
+      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+      the License for the specific language governing rights and limitations
+      under the License.
+    
+    </legalnotice>
+
+    <title>The C Server Back-end</title>
+    <prepared></prepared>
+    <docno></docno>
+    <date>2004-01-14</date>
+    <rev>C</rev>
+    <file>ch_c_server.xml</file>
+  </header>
+
+  <section>
+    <title>Introduction</title>
+    <p>With the option <c>{be, c_server}</c> the IDL Compiler generates
+      C server skeletons according to the IDL to C mapping, on top of
+      the Erlang distribution and gen_server protocols.</p>
+    <p>The developer has to write additional code, that together with
+      the generated C server skeletons, form a hidden Erlang
+      node. That additional code contains implementations of call-back
+      functions that implement the true server functionality, and also
+      code uses <c>erl_interface</c> functions for defining the hidden
+      node and for establishing connections to other Erlang nodes.</p>
+  </section>
+
+  <section>
+    <title>Generated Stub Files</title>
+    <p>The generated stub files are:</p>
+    <list type="bulleted">
+      <item>
+        <p>For each IDL interface, a C source file, the name of which
+          is <c><![CDATA[<Scoped Interface Name>__s.c]]></c>. Each operation of the
+          IDL interface is mapped to a C function (with scoped name)
+          in that file;</p>
+      </item>
+      <item>
+        <p>C source files that contain functions for type conversion,
+          memory allocation, and data encoding/decoding;</p>
+      </item>
+      <item>
+        <p>C header files that contain function prototypes and type
+          definitions.</p>
+      </item>
+    </list>
+    <p>All C functions are exported (i.e. not declared static).</p>
+  </section>
+
+  <section>
+    <title>C Skeleton Functions</title>
+    <p>For each IDL operation a C skeleton function is generated, the
+      prototype of which is <c><![CDATA[int <Scoped Function Name>__exec(<Interface Object> oe_obj, CORBA_Environment *oe_env)]]></c>, where <c><![CDATA[<Interface Object>]]></c>, and
+      <c>CORBA_Environment</c> are of the same type as for the
+      generated C client stubs code.</p>
+    <p>Each <c><![CDATA[<Scoped Function Name>__exec()]]></c> function calls the
+      call-back function</p>
+    <p><c><![CDATA[<Scoped Function Name>_rs* <Scoped Function Name>__cb(<Interface Object> oe_obj, <Parameters>, CORBA_Environment *oe_env)]]></c></p>
+    <p>where the arguments are of the same type as those generated for
+      C client stubs. </p>
+    <p>The return value <c><![CDATA[<Scoped Function Name>_rs* ]]></c> is a pointer
+      to a function with the same signature as the call-back function
+      <c><![CDATA[<Scoped Function Name>_cb]]></c>, and is called after the call-back
+      function has been evaluated (provided that the pointer is not equal
+      to <c>NULL</c>). </p>
+  </section>
+
+  <section>
+    <title>The Server Loop</title>
+    <p>The developer has to implement code for establishing connections
+      with other Erlang nodes, code for call-back functions and restore
+      functions. </p>
+    <p></p>
+    <p>In addition, the developer also has to implement code for a
+      server loop, that receives messages and calls the relevant
+      <c>__exec</c> function. For that purpose the IC library function
+      <c>oe_server_receive()</c> function can be used.</p>
+  </section>
+
+  <section>
+    <title>Generating, Compiling and Linking</title>
+    <p>To generate the C server skeletons type the following in an
+      appropriate shell:</p>
+    <p><c>erlc -I ICROOT/include "+{be, c_server}"  File.idl</c>,</p>
+    <p>where <c>ICROOT</c> is the root of the IC application. The
+      <c>-I ICROOT/include</c> is only needed if <c>File.idl</c>
+      refers to <c>erlang.idl</c>.</p>
+    <p>When compiling a generated C skeleton file, the directories
+      <c>ICROOT/include</c> and <c>EICROOT/include</c>, have to be
+      specified as include directories, where <c>EIROOT</c> is the
+      root directory of the Erl_interface application.</p>
+    <p>When linking object files the <c>EIROOT/lib</c> and
+      <c>ICROOT/priv/lib</c> directories have to be specified. </p>
+  </section>
+
+  <section>
+    <title>An Example</title>
+    <p>In this example the IDL specification file "random.idl" is used
+      for generating C server skeletons (the file is contained in the IC
+      <c>/examples/c-server</c> directory):</p>
+    <code type="none">
+module rmod {
+ 
+  interface random {
+ 
+    double produce();
+ 
+    oneway void init(in long seed1, in long seed2, in long seed3);
+ 
+  };
+ 
+};        </code>
+    <p>Generate the C server skeletons:</p>
+    <code type="none">
+erlc '+{be, c_server}' random.idl
+Erlang IDL compiler version X.Y.Z        </code>
+    <p>Six files are generated. </p>
+    <p>Compile the C server skeletons:</p>
+    <p>Please read the <c>ReadMe</c> file in the
+      <c>examples/c-server</c> directory.</p>
+    <p>In the same directory you can find all the code for this
+      example.  In particular you will find the <c>server.c</c> file
+      that contains all the additional code that must be written to
+      obtain a complete server.</p>
+    <p>In the <c>examples/c-server</c> directory you will also find
+      source code for an Erlang client, which can be used for testing
+      the C server.</p>
+  </section>
+</chapter>
+
+