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16 <p class="apache">Apache HTTP Server Version 2.1</p>
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21 <div id="page-content">
22 <div id="preamble"><h1>Apache Module mod_isapi</h1>
24 <p><span>Available Languages: </span><a href="../en/mod/mod_isapi.html" title="English"> en </a></p>
26 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>ISAPI Extensions within Apache for Windows</td></tr>
27 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
28 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>isapi_module</td></tr>
29 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_isapi.c</td></tr>
30 <tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Win32 only</td></tr></table>
33 <p>This module implements the Internet Server extension API. It
34 allows Internet Server extensions (<em>e.g.</em> ISAPI .dll
35 modules) to be served by Apache for Windows, subject to the
36 noted restrictions.</p>
38 <p>ISAPI extension modules (.dll files) are written by third
39 parties. The Apache Group does not author these modules, so we
40 provide no support for them. Please contact the ISAPI's author
41 directly if you are experiencing problems running their ISAPI
42 extension. <strong>Please <em>do not</em> post such problems to
43 Apache's lists or bug reporting pages.</strong></p>
45 <div id="quickview"><h3 class="directives">Directives</h3>
47 <li><img alt="" src="../images/down.gif" /> <a href="#isapiappendlogtoerrors">ISAPIAppendLogToErrors</a></li>
48 <li><img alt="" src="../images/down.gif" /> <a href="#isapiappendlogtoquery">ISAPIAppendLogToQuery</a></li>
49 <li><img alt="" src="../images/down.gif" /> <a href="#isapicachefile">ISAPICacheFile</a></li>
50 <li><img alt="" src="../images/down.gif" /> <a href="#isapifakeasync">ISAPIFakeAsync</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#isapilognotsupported">ISAPILogNotSupported</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#isapireadaheadbuffer">ISAPIReadAheadBuffer</a></li>
56 <li><img alt="" src="../images/down.gif" /> <a href="#usage">Usage</a></li>
57 <li><img alt="" src="../images/down.gif" /> <a href="#notes">Additional Notes</a></li>
58 <li><img alt="" src="../images/down.gif" /> <a href="#journal">Programmer's Journal</a></li>
60 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
62 <h2><a name="usage" id="usage">Usage</a></h2>
64 <p>In the server configuration file, use
65 the <code class="directive"><a href="../mod/mod_mime.html#addhandler">AddHandler</a></code> directive to
66 associate ISAPI files with the <code>isapi-isa</code> handler, and map
67 it to them with their file extensions. To enable any .dll file to be
68 processed as an ISAPI extension, edit the httpd.conf file and add the
70 <div class="example"><p><code>
71 AddHandler isapi-isa .dll
74 <p>There is no capability within the Apache server to leave a
75 requested module loaded. However, you may preload and keep a
76 specific module loaded by using the following syntax in your
78 <div class="example"><p><code>
79 ISAPICacheFile c:/WebWork/Scripts/ISAPI/mytest.dll
82 <p>Whether or not you have preloaded an ISAPI extension, all
83 ISAPI extensions are governed by the same permissions and
84 restrictions as CGI scripts. That is, <code class="directive"><a href="../mod/core.html#options">Options</a></code> <code>ExecCGI</code> must be set for the
85 directory that contains the ISAPI .dll file.</p>
87 <p>Review the <a href="#notes">Additional Notes</a> and the <a href="#journal">Programmer's Journal</a> for additional details
88 and clarification of the specific ISAPI support offered by
89 <code class="module"><a href="../mod/mod_isapi.html">mod_isapi</a></code>.</p>
90 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
92 <h2><a name="notes" id="notes">Additional Notes</a></h2>
94 <p>Apache's ISAPI implementation conforms to all of the ISAPI
95 2.0 specification, except for some "Microsoft-specific"
96 extensions dealing with asynchronous I/O. Apache's I/O model
97 does not allow asynchronous reading and writing in a manner
98 that the ISAPI could access. If an ISA tries to access
99 unsupported features, including async I/O, a message is placed
100 in the error log to help with debugging. Since these messages
101 can become a flood, the directive <code>ISAPILogNotSupported
102 Off</code> exists to quiet this noise.</p>
104 <p>Some servers, like Microsoft IIS, load the ISAPI extension
105 into the server and keep it loaded until memory usage is too
106 high, or unless configuration options are specified. Apache
107 currently loads and unloads the ISAPI extension each time it is
108 requested, unless the <code class="directive"><a href="#isapicachefile">ISAPICacheFile</a></code> directive is specified.
109 This is inefficient, but Apache's memory model makes this the
110 most effective method. Many ISAPI modules are subtly
111 incompatible with the Apache server, and unloading these
112 modules helps to ensure the stability of the server.</p>
114 <p>Also, remember that while Apache supports ISAPI Extensions,
115 it <strong>does not support ISAPI Filters</strong>. Support for
116 filters may be added at a later date, but no support is planned
118 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
119 <div class="section">
120 <h2><a name="journal" id="journal">Programmer's Journal</a></h2>
122 <p>If you are programming Apache 2.0 <code class="module"><a href="../mod/mod_isapi.html">mod_isapi</a></code>
123 modules, you must limit your calls to <code>ServerSupportFunction</code>
124 to the following directives:</p>
127 <dt><code>HSE_REQ_SEND_URL_REDIRECT_RESP</code></dt>
128 <dd>Redirect the user to another location.<br />
129 This must be a fully qualified URL (<em>e.g.</em>
130 <code>http://server/location</code>).</dd>
132 <dt><code>HSE_REQ_SEND_URL</code></dt>
133 <dd>Redirect the user to another location.<br />
134 This cannot be a fully qualified URL, you are not allowed to
135 pass the protocol or a server name (<em>e.g.</em> simply
136 <code>/location</code>).<br />
137 This redirection is handled by the server, not the
139 <div class="warning"><h3>Warning</h3>
140 <p>In their recent documentation, Microsoft appears to have
141 abandoned the distinction between the two
142 <code>HSE_REQ_SEND_URL</code> functions. Apache continues to treat
143 them as two distinct functions with different requirements
147 <dt><code>HSE_REQ_SEND_RESPONSE_HEADER</code></dt>
148 <dd>Apache accepts a response body following the header if it
149 follows the blank line (two consecutive newlines) in the
150 headers string argument. This body cannot contain NULLs,
151 since the headers argument is NULL terminated.</dd>
153 <dt><code>HSE_REQ_DONE_WITH_SESSION</code></dt>
154 <dd>Apache considers this a no-op, since the session will be
155 finished when the ISAPI returns from processing.</dd>
157 <dt><code>HSE_REQ_MAP_URL_TO_PATH</code></dt>
158 <dd>Apache will translate a virtual name to a physical
161 <dt><code>HSE_APPEND_LOG_PARAMETER</code></dt>
163 This logged message may be captured in any of the following
167 <li>in the <code>\"%{isapi-parameter}n\"</code> component in a
168 <code class="directive"><a href="../mod/mod_log_config.html#customlog">CustomLog</a></code>
171 <li>in the <code>%q</code> log component with the
172 <code class="directive"><a href="#isapiappendlogtoquery">ISAPIAppendLogToQuery</a></code>
173 <code>On</code> directive</li>
175 <li>in the error log with the <code class="directive"><a href="#isapiappendlogtoerrors">ISAPIAppendLogToErrors</a></code> <code>On</code> directive</li>
178 <p>The first option, the <code>%{isapi-parameter}n</code> component,
179 is always available and preferred.</p>
182 <dt><code>HSE_REQ_IS_KEEP_CONN</code></dt>
183 <dd>Will return the negotiated Keep-Alive status.</dd>
185 <dt><code>HSE_REQ_SEND_RESPONSE_HEADER_EX</code></dt>
186 <dd>Will behave as documented, although the <code>fKeepConn</code>
187 flag is ignored.</dd>
189 <dt><code>HSE_REQ_IS_CONNECTED</code></dt>
190 <dd>Will report false if the request has been aborted.</dd>
193 <p>Apache returns <code>FALSE</code> to any unsupported call to
194 <code>ServerSupportFunction</code>, and sets the
195 <code>GetLastError</code> value to
196 <code>ERROR_INVALID_PARAMETER</code>.</p>
198 <p><code>ReadClient</code> retrieves the request body exceeding the
199 initial buffer (defined by <code class="directive"><a href="#isapireadaheadbuffer">ISAPIReadAheadBuffer</a></code>). Based on the
200 <code class="directive">ISAPIReadAheadBuffer</code> setting (number of bytes
201 to buffer prior to calling the ISAPI handler) shorter requests are sent
202 complete to the extension when it is invoked. If the request is
203 longer, the ISAPI extension must use <code>ReadClient</code> to
204 retrieve the remaining request body.</p>
206 <p><code>WriteClient</code> is supported, but only with the
207 <code>HSE_IO_SYNC</code> flag or no option flag (value of
208 <code>0</code>). Any other <code>WriteClient</code> request
209 will be rejected with a return value of <code>FALSE</code>, and a
210 <code>GetLastError</code> value of
211 <code>ERROR_INVALID_PARAMETER</code>.</p>
213 <p><code>GetServerVariable</code> is supported, although extended server
214 variables do not exist (as defined by other servers.) All the
215 usual Apache CGI environment variables are available from
216 <code>GetServerVariable</code>, as well as the <code>ALL_HTTP</code>
217 and <code>ALL_RAW</code> values.</p>
219 <p>Apache 2.0 <code class="module"><a href="../mod/mod_isapi.html">mod_isapi</a></code> supports additional
220 features introduced in later versions of the ISAPI specification,
221 as well as limited emulation of async I/O and the
222 <code>TransmitFile</code> semantics. Apache also supports preloading
223 ISAPI .dlls for performance, neither of which were not available under
224 Apache 1.3 <code>mod_isapi</code>.</p>
226 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
227 <div class="directive-section"><h2><a name="ISAPIAppendLogToErrors" id="ISAPIAppendLogToErrors">ISAPIAppendLogToErrors</a> <a name="isapiappendlogtoerrors" id="isapiappendlogtoerrors">Directive</a></h2>
228 <table class="directive">
229 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Record HSE_APPEND_LOG_PARAMETER requests from
230 ISAPI extensions to the error log</td></tr>
231 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPIAppendLogToErrors on|off</code></td></tr>
232 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ISAPIAppendLogToErrors off</code></td></tr>
233 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
234 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
235 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
236 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
238 <p>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from ISAPI
239 extensions to the server error log.</p>
242 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
243 <div class="directive-section"><h2><a name="ISAPIAppendLogToQuery" id="ISAPIAppendLogToQuery">ISAPIAppendLogToQuery</a> <a name="isapiappendlogtoquery" id="isapiappendlogtoquery">Directive</a></h2>
244 <table class="directive">
245 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Record HSE_APPEND_LOG_PARAMETER requests from
246 ISAPI extensions to the query field</td></tr>
247 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPIAppendLogToQuery on|off</code></td></tr>
248 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ISAPIAppendLogToQuery on</code></td></tr>
249 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
250 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
251 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
252 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
254 <p>Record <code>HSE_APPEND_LOG_PARAMETER</code> requests from ISAPI
255 extensions to the query field (appended to the <code class="directive"><a href="../mod/mod_log_config.html#customlog">CustomLog</a></code> <code>%q</code>
259 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
260 <div class="directive-section"><h2><a name="ISAPICacheFile" id="ISAPICacheFile">ISAPICacheFile</a> <a name="isapicachefile" id="isapicachefile">Directive</a></h2>
261 <table class="directive">
262 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>ISAPI .dll files to be loaded at startup</td></tr>
263 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPICacheFile <var>file-path</var> [<var>file-path</var>]
265 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
266 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
267 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
269 <p>Specifies a space-separated list of file names to be loaded
270 when the Apache server is launched, and remain loaded until the
271 server is shut down. This directive may be repeated for every
272 ISAPI .dll file desired. The full path name of each file should
273 be specified. If the path name is not absolute, it will be treated
274 relative to <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
277 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
278 <div class="directive-section"><h2><a name="ISAPIFakeAsync" id="ISAPIFakeAsync">ISAPIFakeAsync</a> <a name="isapifakeasync" id="isapifakeasync">Directive</a></h2>
279 <table class="directive">
280 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Fake asynchronous support for ISAPI callbacks</td></tr>
281 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPIFakeAsync on|off</code></td></tr>
282 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ISAPIFakeAsync off</code></td></tr>
283 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
284 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
285 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
286 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
288 <p>While set to on, asynchronous support for ISAPI callbacks is
292 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
293 <div class="directive-section"><h2><a name="ISAPILogNotSupported" id="ISAPILogNotSupported">ISAPILogNotSupported</a> <a name="isapilognotsupported" id="isapilognotsupported">Directive</a></h2>
294 <table class="directive">
295 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Log unsupported feature requests from ISAPI
297 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPILogNotSupported on|off</code></td></tr>
298 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ISAPILogNotSupported off</code></td></tr>
299 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
300 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
301 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
302 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
304 <p>Logs all requests for unsupported features from ISAPI
305 extensions in the server error log. This may help administrators
306 to track down problems. Once set to on and all desired ISAPI modules
307 are functioning, it should be set back to off.</p>
310 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
311 <div class="directive-section"><h2><a name="ISAPIReadAheadBuffer" id="ISAPIReadAheadBuffer">ISAPIReadAheadBuffer</a> <a name="isapireadaheadbuffer" id="isapireadaheadbuffer">Directive</a></h2>
312 <table class="directive">
313 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Size of the Read Ahead Buffer sent to ISAPI
315 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ISAPIReadAheadBuffer <var>size</var></code></td></tr>
316 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ISAPIReadAheadBuffer 49152</code></td></tr>
317 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
318 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
319 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
320 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_isapi</td></tr>
322 <p>Defines the maximum size of the Read Ahead Buffer sent to
323 ISAPI extensions when they are initially invoked. All remaining
324 data must be retrieved using the <code>ReadClient</code> callback; some
325 ISAPI extensions may not support the <code>ReadClient</code> function.
326 Refer questions to the ISAPI extension's author.</p>
330 <div class="bottomlang">
331 <p><span>Available Languages: </span><a href="../en/mod/mod_isapi.html" title="English"> en </a></p>
332 </div><div id="footer">
333 <p class="apache">Copyright 1999-2004 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>
334 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>