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472N/A<title>Converting Modules from Apache 1.3 to Apache 2.0 - Apache HTTP Server</title>
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472N/A<p class="apache">Apache HTTP Server Version 2.5</p>
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472N/A<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.5</a> &gt; <a href="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Converting Modules from Apache 1.3 to Apache 2.0</h1>
472N/A<div class="toplang">
472N/A<p><span>Available Languages: </span><a href="/en/developer/modules.html" title="English">&nbsp;en&nbsp;</a> |
472N/A<a href="/ja/developer/modules.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
472N/A</div>
472N/A
472N/A <p>This is a first attempt at writing the lessons I learned
472N/A when trying to convert the <code>mod_mmap_static</code> module to Apache
472N/A 2.0. It's by no means definitive and probably won't even be
472N/A correct in some ways, but it's a start.</p>
472N/A</div>
472N/A<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#easy">The easier changes ...</a></li>
472N/A<li><img alt="" src="/images/down.gif" /> <a href="#messy">The messier changes...</a></li>
472N/A</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
472N/A<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
472N/A<div class="section">
472N/A<h2><a name="easy" id="easy">The easier changes ...</a></h2>
472N/A
472N/A <h3><a name="cleanup" id="cleanup">Cleanup Routines</a></h3>
472N/A <p>These now need to be of type <code>apr_status_t</code> and return a
472N/A value of that type. Normally the return value will be
472N/A <code>APR_SUCCESS</code> unless there is some need to signal an error in
472N/A the cleanup. Be aware that even though you signal an error not all code
472N/A yet checks and acts upon the error.</p>
472N/A
472N/A
472N/A <h3><a name="init" id="init">Initialisation Routines</a></h3>
472N/A <p>These should now be renamed to better signify where they sit
472N/A in the overall process. So the name gets a small change from
472N/A <code>mmap_init</code> to <code>mmap_post_config</code>. The arguments
472N/A passed have undergone a radical change and now look like</p>
472N/A
472N/A <ul>
472N/A <li><code>apr_pool_t *p</code></li>
472N/A <li><code>apr_pool_t *plog</code></li>
472N/A <li><code>apr_pool_t *ptemp</code></li>
472N/A <li><code>server_rec *s</code></li>
472N/A </ul>
472N/A
472N/A
472N/A <h3><a name="datatypes" id="datatypes">Data Types</a></h3>
472N/A <p>A lot of the data types have been moved into the <a href="http://apr.apache.org/">APR</a>. This means that some have had
472N/A a name change, such as the one shown above. The following is a brief
472N/A list of some of the changes that you are likely to have to make.</p>
472N/A
472N/A <ul>
472N/A <li><code>pool</code> becomes <code>apr_pool_t</code></li>
472N/A <li><code>table</code> becomes <code>apr_table_t</code></li>
472N/A </ul>
472N/A
</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
<div class="section">
<h2><a name="messy" id="messy">The messier changes...</a></h2>
<h3><a name="register-hooks" id="register-hooks">Register Hooks</a></h3>
<p>The new architecture uses a series of hooks to provide for
calling your functions. These you'll need to add to your module
by way of a new function, <code>static void register_hooks(void)</code>.
The function is really reasonably straightforward once you
understand what needs to be done. Each function that needs
calling at some stage in the processing of a request needs to
be registered, handlers do not. There are a number of phases
where functions can be added, and for each you can specify with
a high degree of control the relative order that the function
will be called in.</p>
<p>This is the code that was added to <code>mod_mmap_static</code>:</p>
<div class="example"><pre>
static void register_hooks(void)
{
static const char * const aszPre[]={ "http_core.c",NULL };
ap_hook_post_config(mmap_post_config,NULL,NULL,HOOK_MIDDLE);
ap_hook_translate_name(mmap_static_xlat,aszPre,NULL,HOOK_LAST);
};</pre></div>
<p>This registers 2 functions that need to be called, one in
the <code>post_config</code> stage (virtually every module will need this
one) and one for the <code>translate_name</code> phase. note that while
there are different function names the format of each is
identical. So what is the format?</p>
<div class="example"><p><code>
ap_hook_<var>phase_name</var>(<var>function_name</var>,
<var>predecessors</var>, <var>successors</var>, <var>position</var>);
</code></p></div>
<p>There are 3 hook positions defined...</p>
<ul>
<li><code>HOOK_FIRST</code></li>
<li><code>HOOK_MIDDLE</code></li>
<li><code>HOOK_LAST</code></li>
</ul>
<p>To define the position you use the position and then modify
it with the predecessors and successors. Each of the modifiers
can be a list of functions that should be called, either before
the function is run (predecessors) or after the function has
run (successors).</p>
<p>In the <code>mod_mmap_static</code> case I didn't care about the
<code>post_config</code> stage, but the <code>mmap_static_xlat</code>
<strong>must</strong> be called after the core module had done it's name
translation, hence the use of the aszPre to define a modifier to the
position <code>HOOK_LAST</code>.</p>
<h3><a name="moddef" id="moddef">Module Definition</a></h3>
<p>There are now a lot fewer stages to worry about when
creating your module definition. The old definition looked
like</p>
<div class="example"><pre>
module MODULE_VAR_EXPORT <var>module_name</var>_module =
{
STANDARD_MODULE_STUFF,
/* initializer */
/* dir config creater */
/* dir merger --- default is to override */
/* server config */
/* merge server config */
/* command handlers */
/* handlers */
/* filename translation */
/* check_user_id */
/* check auth */
/* check access */
/* type_checker */
/* fixups */
/* logger */
/* header parser */
/* child_init */
/* child_exit */
/* post read-request */
};</pre></div>
<p>The new structure is a great deal simpler...</p>
<div class="example"><pre>
module MODULE_VAR_EXPORT <var>module_name</var>_module =
{
STANDARD20_MODULE_STUFF,
/* create per-directory config structures */
/* merge per-directory config structures */
/* create per-server config structures */
/* merge per-server config structures */
/* command handlers */
/* handlers */
/* register hooks */
};</pre></div>
<p>Some of these read directly across, some don't. I'll try to
summarise what should be done below.</p>
<p>The stages that read directly across :</p>
<dl>
<dt><code>/* dir config creater */</code></dt>
<dd><code>/* create per-directory config structures */</code></dd>
<dt><code>/* server config */</code></dt>
<dd><code>/* create per-server config structures */</code></dd>
<dt><code>/* dir merger */</code></dt>
<dd><code>/* merge per-directory config structures */</code></dd>
<dt><code>/* merge server config */</code></dt>
<dd><code>/* merge per-server config structures */</code></dd>
<dt><code>/* command table */</code></dt>
<dd><code>/* command apr_table_t */</code></dd>
<dt><code>/* handlers */</code></dt>
<dd><code>/* handlers */</code></dd>
</dl>
<p>The remainder of the old functions should be registered as
hooks. There are the following hook stages defined so
far...</p>
<dl>
<dt><code>ap_hook_pre_config</code></dt>
<dd>do any setup required prior to processing configuration
directives</dd>
<dt><code>ap_hook_check_config</code></dt>
<dd>review configuration directive interdependencies</dd>
<dt><code>ap_hook_test_config</code></dt>
<dd>executes only with <code>-t</code> option</dd>
<dt><code>ap_hook_open_logs</code></dt>
<dd>open any specified logs</dd>
<dt><code>ap_hook_post_config</code></dt>
<dd>this is where the old <code>_init</code> routines get
registered</dd>
<dt><code>ap_hook_http_method</code></dt>
<dd>retrieve the http method from a request. (legacy)</dd>
<dt><code>ap_hook_auth_checker</code></dt>
<dd>check if the resource requires authorization</dd>
<dt><code>ap_hook_access_checker</code></dt>
<dd>check for module-specific restrictions</dd>
<dt><code>ap_hook_check_user_id</code></dt>
<dd>check the user-id and password</dd>
<dt><code>ap_hook_default_port</code></dt>
<dd>retrieve the default port for the server</dd>
<dt><code>ap_hook_pre_connection</code></dt>
<dd>do any setup required just before processing, but after
accepting</dd>
<dt><code>ap_hook_process_connection</code></dt>
<dd>run the correct protocol</dd>
<dt><code>ap_hook_child_init</code></dt>
<dd>call as soon as the child is started</dd>
<dt><code>ap_hook_create_request</code></dt>
<dd>??</dd>
<dt><code>ap_hook_fixups</code></dt>
<dd>last chance to modify things before generating content</dd>
<dt><code>ap_hook_handler</code></dt>
<dd>generate the content</dd>
<dt><code>ap_hook_header_parser</code></dt>
<dd>lets modules look at the headers, not used by most modules, because
they use <code>post_read_request</code> for this</dd>
<dt><code>ap_hook_insert_filter</code></dt>
<dd>to insert filters into the filter chain</dd>
<dt><code>ap_hook_log_transaction</code></dt>
<dd>log information about the request</dd>
<dt><code>ap_hook_optional_fn_retrieve</code></dt>
<dd>retrieve any functions registered as optional</dd>
<dt><code>ap_hook_post_read_request</code></dt>
<dd>called after reading the request, before any other phase</dd>
<dt><code>ap_hook_quick_handler</code></dt>
<dd>called before any request processing, used by cache modules.</dd>
<dt><code>ap_hook_translate_name</code></dt>
<dd>translate the URI into a filename</dd>
<dt><code>ap_hook_type_checker</code></dt>
<dd>determine and/or set the doc type</dd>
</dl>
</div></div>
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