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      <holder>Ericsson AB. All Rights Reserved.</holder>
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      The contents of this file are subject to the Erlang Public License,
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    <title>Using the IC Compiler</title>
    <prepared></prepared>
    <docno></docno>
    <date>2002-08-02</date>
    <rev>PB1</rev>
    <file>ch_introduction.xml</file>
  </header>

  <section>
    <title>Introduction</title>
    <p>The IC application is an IDL compiler implemented in Erlang.
      The IDL compiler generates client stubs and server skeletons.
      Several back-ends are supported, and they fall into three main
      groups.</p>
    <p>The first group consists of a CORBA back-end:</p>
    <taglist>
      <tag>IDL to Erlang CORBA</tag>
      <item>
        <p>This back-end is for CORBA communication and implementation,
          and the generated code uses the CORBA specific protocol for
          communication between clients and servers. See the
          <em>Orber</em> application User's Guide and manuals for
          further details.</p>
      </item>
    </taglist>
    <p>The second group consists of a simple Erlang back-end:</p>
    <taglist>
      <tag>IDL to plain Erlang</tag>
      <item>
        <p>This back-end provides a very simple Erlang client
          interface. It can only be used within an Erlang node,
          and the communication between client and "server" is
          therefore in terms of ordinary function calls. </p>
        <p>This back-end can be considered a short-circuit version of
          the IDL to Erlang gen_server back-end (see further below).</p>
      </item>
    </taglist>
    <p>The third group consists of backends for Erlang, C, and
      Java. The communication between clients and servers is by the
      Erlang distribution protocol, facilitated by
      <em>erl_interface</em> and <em>jinterface</em> for C and Java,
      respectively.</p>
    <p>All back-ends of the third group generate code compatible with
      the Erlang gen_server behavior protocol. Thus generated client
      code corresponds to <c>call()</c> or <c>cast()</c> of an Erlang
      <c>gen_server</c>. Similarly, generated server code corresponds
      to <c>handle_call()</c> or <c>handle_cast()</c> of an Erlang
      <c>gen_server</c>.</p>
    <p>The back-ends of the third group are:
      </p>
    <taglist>
      <tag>IDL to Erlang gen_server</tag>
      <item>
        <p>Client stubs and server skeletons are generated. Data types
          are mapped according to the IDL to Erlang mapping described
          in the <em>Orber User's Guide</em>.</p>
        <p></p>
      </item>
      <tag>IDL to C client</tag>
      <item>
        <p>Client stubs are generated. The mapping of data types is
          described further on in the C client part of this guide.</p>
      </item>
      <tag>IDL to C server</tag>
      <item>
        <p>Server skeletons are generated. The mapping of data types is
          described further on in the C server part of this guide.</p>
      </item>
      <tag>IDL to Java</tag>
      <item>
        <p>Client stubs and server skeletons are generated. The mapping
          of data types is described further on in the Java part of
          this guide.</p>
      </item>
    </taglist>
  </section>

  <section>
    <title>Compilation of IDL Files</title>
    <p>The IC compiler is invoked by executing the generic <c>erlc</c>
      compiler from a shell:</p>
    <code type="none">
%> erlc +'{be,BackEnd}' File.idl
    </code>
    <p>where <c>BackEnd</c> is according to the table below, and
      <c>File.idl</c> is the IDL file to be compiled.</p>
    <table>
      <row>
        <cell align="left" valign="middle"><em>Back-end</em></cell>
        <cell align="left" valign="middle"><c>BackEnd</c>option</cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to CORBA</cell>
        <cell align="left" valign="middle"><c>erl_corba</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to CORBA template</cell>
        <cell align="left" valign="middle"><c>erl_template</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to plain Erlang</cell>
        <cell align="left" valign="middle"><c>erl_plain</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to Erlang gen_server</cell>
        <cell align="left" valign="middle"><c>erl_genserv</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to C client</cell>
        <cell align="left" valign="middle"><c>c_client</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to C server</cell>
        <cell align="left" valign="middle"><c>c_server</c></cell>
      </row>
      <row>
        <cell align="left" valign="middle">IDL to Java</cell>
        <cell align="left" valign="middle"><c>java</c></cell>
      </row>
      <tcaption>Compiler back-ends and options</tcaption>
    </table>
    <p>For more details on IC compiler options consult the ic(3) manual page.</p>
  </section>
</chapter>

