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15 <p class="apache">Apache HTTP Server Version 2.3</p>
16 <img alt="" src="../images/feather.gif" /></div>
17 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
19 <a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <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>
21 <p><span>Available Languages: </span><a href="../en/developer/modules.html" title="English"> en </a> |
22 <a href="../ja/developer/modules.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
25 <p>This is a first attempt at writing the lessons I learned
26 when trying to convert the <code>mod_mmap_static</code> module to Apache
27 2.0. It's by no means definitive and probably won't even be
28 correct in some ways, but it's a start.</p>
30 <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#easy">The easier changes ...</a></li>
31 <li><img alt="" src="../images/down.gif" /> <a href="#messy">The messier changes...</a></li>
33 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
35 <h2><a name="easy" id="easy">The easier changes ...</a></h2>
37 <h3><a name="cleanup" id="cleanup">Cleanup Routines</a></h3>
38 <p>These now need to be of type <code>apr_status_t</code> and return a
39 value of that type. Normally the return value will be
40 <code>APR_SUCCESS</code> unless there is some need to signal an error in
41 the cleanup. Be aware that even though you signal an error not all code
42 yet checks and acts upon the error.</p>
45 <h3><a name="init" id="init">Initialisation Routines</a></h3>
46 <p>These should now be renamed to better signify where they sit
47 in the overall process. So the name gets a small change from
48 <code>mmap_init</code> to <code>mmap_post_config</code>. The arguments
49 passed have undergone a radical change and now look like</p>
52 <li><code>apr_pool_t *p</code></li>
53 <li><code>apr_pool_t *plog</code></li>
54 <li><code>apr_pool_t *ptemp</code></li>
55 <li><code>server_rec *s</code></li>
59 <h3><a name="datatypes" id="datatypes">Data Types</a></h3>
60 <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
61 a name change, such as the one shown above. The following is a brief
62 list of some of the changes that you are likely to have to make.</p>
65 <li><code>pool</code> becomes <code>apr_pool_t</code></li>
66 <li><code>table</code> becomes <code>apr_table_t</code></li>
69 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
71 <h2><a name="messy" id="messy">The messier changes...</a></h2>
73 <h3><a name="register-hooks" id="register-hooks">Register Hooks</a></h3>
74 <p>The new architecture uses a series of hooks to provide for
75 calling your functions. These you'll need to add to your module
76 by way of a new function, <code>static void register_hooks(void)</code>.
77 The function is really reasonably straightforward once you
78 understand what needs to be done. Each function that needs
79 calling at some stage in the processing of a request needs to
80 be registered, handlers do not. There are a number of phases
81 where functions can be added, and for each you can specify with
82 a high degree of control the relative order that the function
83 will be called in.</p>
85 <p>This is the code that was added to <code>mod_mmap_static</code>:</p>
86 <div class="example"><pre>
87 static void register_hooks(void)
89 static const char * const aszPre[]={ "http_core.c",NULL };
90 ap_hook_post_config(mmap_post_config,NULL,NULL,HOOK_MIDDLE);
91 ap_hook_translate_name(mmap_static_xlat,aszPre,NULL,HOOK_LAST);
94 <p>This registers 2 functions that need to be called, one in
95 the <code>post_config</code> stage (virtually every module will need this
96 one) and one for the <code>translate_name</code> phase. note that while
97 there are different function names the format of each is
98 identical. So what is the format?</p>
100 <div class="example"><p><code>
101 ap_hook_<var>phase_name</var>(<var>function_name</var>,
102 <var>predecessors</var>, <var>successors</var>, <var>position</var>);
105 <p>There are 3 hook positions defined...</p>
108 <li><code>HOOK_FIRST</code></li>
109 <li><code>HOOK_MIDDLE</code></li>
110 <li><code>HOOK_LAST</code></li>
113 <p>To define the position you use the position and then modify
114 it with the predecessors and successors. Each of the modifiers
115 can be a list of functions that should be called, either before
116 the function is run (predecessors) or after the function has
117 run (successors).</p>
119 <p>In the <code>mod_mmap_static</code> case I didn't care about the
120 <code>post_config</code> stage, but the <code>mmap_static_xlat</code>
121 <strong>must</strong> be called after the core module had done it's name
122 translation, hence the use of the aszPre to define a modifier to the
123 position <code>HOOK_LAST</code>.</p>
126 <h3><a name="moddef" id="moddef">Module Definition</a></h3>
127 <p>There are now a lot fewer stages to worry about when
128 creating your module definition. The old defintion looked
131 <div class="example"><pre>
132 module MODULE_VAR_EXPORT <var>module_name</var>_module =
134 STANDARD_MODULE_STUFF,
136 /* dir config creater */
137 /* dir merger --- default is to override */
139 /* merge server config */
140 /* command handlers */
142 /* filename translation */
152 /* post read-request */
155 <p>The new structure is a great deal simpler...</p>
156 <div class="example"><pre>
157 module MODULE_VAR_EXPORT <var>module_name</var>_module =
159 STANDARD20_MODULE_STUFF,
160 /* create per-directory config structures */
161 /* merge per-directory config structures */
162 /* create per-server config structures */
163 /* merge per-server config structures */
164 /* command handlers */
169 <p>Some of these read directly across, some don't. I'll try to
170 summarise what should be done below.</p>
172 <p>The stages that read directly across :</p>
175 <dt><code>/* dir config creater */</code></dt>
176 <dd><code>/* create per-directory config structures */</code></dd>
178 <dt><code>/* server config */</code></dt>
179 <dd><code>/* create per-server config structures */</code></dd>
181 <dt><code>/* dir merger */</code></dt>
182 <dd><code>/* merge per-directory config structures */</code></dd>
184 <dt><code>/* merge server config */</code></dt>
185 <dd><code>/* merge per-server config structures */</code></dd>
187 <dt><code>/* command table */</code></dt>
188 <dd><code>/* command apr_table_t */</code></dd>
190 <dt><code>/* handlers */</code></dt>
191 <dd><code>/* handlers */</code></dd>
194 <p>The remainder of the old functions should be registered as
195 hooks. There are the following hook stages defined so
199 <dt><code>ap_hook_pre_config</code></dt>
200 <dd>do any setup required prior to processing configuration
203 <dt><code>ap_hook_check_config</code></dt>
204 <dd>review configuration directive interdependencies</dd>
206 <dt><code>ap_hook_test_config</code></dt>
207 <dd>executes only with <code>-t</code> option</dd>
209 <dt><code>ap_hook_open_logs</code></dt>
210 <dd>open any specified logs</dd>
212 <dt><code>ap_hook_post_config</code></dt>
213 <dd>this is where the old <code>_init</code> routines get
216 <dt><code>ap_hook_http_method</code></dt>
217 <dd>retrieve the http method from a request. (legacy)</dd>
219 <dt><code>ap_hook_auth_checker</code></dt>
220 <dd>check if the resource requires authorization</dd>
222 <dt><code>ap_hook_access_checker</code></dt>
223 <dd>check for module-specific restrictions</dd>
225 <dt><code>ap_hook_check_user_id</code></dt>
226 <dd>check the user-id and password</dd>
228 <dt><code>ap_hook_default_port</code></dt>
229 <dd>retrieve the default port for the server</dd>
231 <dt><code>ap_hook_pre_connection</code></dt>
232 <dd>do any setup required just before processing, but after
235 <dt><code>ap_hook_process_connection</code></dt>
236 <dd>run the correct protocol</dd>
238 <dt><code>ap_hook_child_init</code></dt>
239 <dd>call as soon as the child is started</dd>
241 <dt><code>ap_hook_create_request</code></dt>
244 <dt><code>ap_hook_fixups</code></dt>
245 <dd>last chance to modify things before generating content</dd>
247 <dt><code>ap_hook_handler</code></dt>
248 <dd>generate the content</dd>
250 <dt><code>ap_hook_header_parser</code></dt>
251 <dd>lets modules look at the headers, not used by most modules, because
252 they use <code>post_read_request</code> for this</dd>
254 <dt><code>ap_hook_insert_filter</code></dt>
255 <dd>to insert filters into the filter chain</dd>
257 <dt><code>ap_hook_log_transaction</code></dt>
258 <dd>log information about the request</dd>
260 <dt><code>ap_hook_optional_fn_retrieve</code></dt>
261 <dd>retrieve any functions registered as optional</dd>
263 <dt><code>ap_hook_post_read_request</code></dt>
264 <dd>called after reading the request, before any other phase</dd>
266 <dt><code>ap_hook_quick_handler</code></dt>
267 <dd>called before any request processing, used by cache modules.</dd>
269 <dt><code>ap_hook_translate_name</code></dt>
270 <dd>translate the URI into a filename</dd>
272 <dt><code>ap_hook_type_checker</code></dt>
273 <dd>determine and/or set the doc type</dd>
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281 <p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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