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| <modulesynopsis metafile="mod_mime_magic.xml.meta"> |
| |
| <name>mod_mime_magic</name> |
| <description>Determines the MIME type of a file |
| by looking at a few bytes of its contents</description> |
| <status>Extension</status> |
| <sourcefile>mod_mime_magic.c</sourcefile> |
| <identifier>mime_magic_module</identifier> |
| |
| <summary> |
| <p>This module determines the <glossary ref="mime-type">MIME |
| type</glossary> of files in the same way the Unix |
| <code>file(1)</code> command works: it looks at the first few |
| bytes of the file. It is intended as a "second line of defense" |
| for cases that <module>mod_mime</module> can't resolve.</p> |
| |
| <p>This module is derived from a free version of the |
| <code>file(1)</code> command for Unix, which uses "magic |
| numbers" and other hints from a file's contents to figure out |
| what the contents are. This module is active only if the magic |
| file is specified by the <directive module="mod_mime_magic" |
| >MimeMagicFile</directive> directive.</p> |
| </summary> |
| |
| <section id="format"><title>Format of the Magic File</title> |
| |
| <p>The contents of the file are plain ASCII text in 4-5 |
| columns. Blank lines are allowed but ignored. Commented lines |
| use a hash mark (<code>#</code>). The remaining lines are parsed for |
| the following columns:</p> |
| |
| <table style="zebra" border="1"> |
| <columnspec><column width=".15"/><column width=".8"/></columnspec> |
| <tr><th>Column</th><th>Description</th></tr> |
| <tr><td>1</td> |
| <td>byte number to begin checking from<br /> |
| "<code>></code>" indicates a dependency upon the previous |
| non-"<code>></code>" line</td></tr> |
| |
| <tr><td>2</td> |
| <td><p>type of data to match</p> |
| <table border="1"> |
| <columnspec><column width=".2"/><column width=".7"/></columnspec> |
| <tr><td><code>byte</code></td> |
| <td>single character</td></tr> |
| <tr><td><code>short</code></td> |
| <td>machine-order 16-bit integer</td></tr> |
| <tr><td><code>long</code></td> |
| <td>machine-order 32-bit integer</td></tr> |
| <tr><td><code>string</code></td> |
| <td>arbitrary-length string</td></tr> |
| <tr><td><code>date</code></td> |
| <td>long integer date (seconds since Unix epoch/1970)</td></tr> |
| <tr><td><code>beshort</code></td> |
| <td>big-endian 16-bit integer</td></tr> |
| <tr><td><code>belong</code></td> |
| <td>big-endian 32-bit integer</td></tr> |
| <tr><td><code>bedate</code></td> |
| <td>big-endian 32-bit integer date</td></tr> |
| <tr><td><code>leshort</code></td> |
| <td>little-endian 16-bit integer</td></tr> |
| <tr><td><code>lelong</code></td> |
| <td>little-endian 32-bit integer</td></tr> |
| <tr><td><code>ledate</code></td> |
| <td>little-endian 32-bit integer date</td></tr> |
| </table></td></tr> |
| |
| <tr><td>3</td> |
| <td>contents of data to match</td></tr> |
| |
| <tr><td>4</td> |
| <td>MIME type if matched</td></tr> |
| |
| <tr><td>5</td> |
| <td>MIME encoding if matched (optional)</td></tr> |
| </table> |
| |
| <p>For example, the following magic file lines would recognize |
| some audio formats:</p> |
| |
| <example> |
| <pre># Sun/NeXT audio data |
| 0 string .snd |
| >12 belong 1 audio/basic |
| >12 belong 2 audio/basic |
| >12 belong 3 audio/basic |
| >12 belong 4 audio/basic |
| >12 belong 5 audio/basic |
| >12 belong 6 audio/basic |
| >12 belong 7 audio/basic |
| >12 belong 23 audio/x-adpcm</pre> |
| </example> |
| |
| <p>Or these would recognize the difference between <code>*.doc</code> |
| files containing Microsoft Word or FrameMaker documents. (These are |
| incompatible file formats which use the same file suffix.)</p> |
| |
| <example> |
| <pre># Frame |
| 0 string \<MakerFile application/x-frame |
| 0 string \<MIFFile application/x-frame |
| 0 string \<MakerDictionary application/x-frame |
| 0 string \<MakerScreenFon application/x-frame |
| 0 string \<MML application/x-frame |
| 0 string \<Book application/x-frame |
| 0 string \<Maker application/x-frame |
| |
| # MS-Word |
| 0 string \376\067\0\043 application/msword |
| 0 string \320\317\021\340\241\261 application/msword |
| 0 string \333\245-\0\0\0 application/msword</pre> |
| </example> |
| |
| <p>An optional MIME encoding can be included as a fifth column. |
| For example, this can recognize gzipped files and set the |
| encoding for them.</p> |
| |
| <example> |
| <pre># gzip (GNU zip, not to be confused with |
| # [Info-ZIP/PKWARE] zip archiver) |
| |
| 0 string \037\213 application/octet-stream x-gzip</pre> |
| </example> |
| </section> |
| |
| <section id="performance"><title>Performance Issues</title> |
| <p>This module is not for every system. If your system is barely |
| keeping up with its load or if you're performing a web server |
| benchmark, you may not want to enable this because the |
| processing is not free.</p> |
| |
| <p>However, an effort was made to improve the performance of |
| the original <code>file(1)</code> code to make it fit in a busy web |
| server. It was designed for a server where there are thousands of users |
| who publish their own documents. This is probably very common |
| on intranets. Many times, it's helpful if the server can make |
| more intelligent decisions about a file's contents than the |
| file name allows ...even if just to reduce the "why doesn't my |
| page work" calls when users improperly name their own files. |
| You have to decide if the extra work suits your |
| environment.</p> |
| </section> |
| |
| <section id="notes"><title>Notes</title> |
| <p>The following notes apply to the <module>mod_mime_magic</module> |
| module and are included here for compliance with contributors' |
| copyright restrictions that require their acknowledgment.</p> |
| |
| <note> |
| <p>mod_mime_magic: MIME type lookup via file magic numbers<br /> |
| Copyright (c) 1996-1997 Cisco Systems, Inc.</p> |
| |
| <p>This software was submitted by Cisco Systems to the Apache Group |
| in July 1997. Future revisions and derivatives of this source code |
| must acknowledge Cisco Systems as the original contributor of this |
| module. All other licensing and usage conditions are those of the |
| Apache Group.</p> |
| |
| <p>Some of this code is derived from the free version of the file |
| command originally posted to comp.sources.unix. Copyright info for |
| that program is included below as required.</p> |
| </note> |
| |
| <note> |
| <p> - Copyright (c) Ian F. Darwin, 1987. Written by Ian F. Darwin.</p> |
| |
| <p>This software is not subject to any license of the American |
| Telephone and Telegraph Company or of the Regents of the University |
| of California.</p> |
| |
| <p>Permission is granted to anyone to use this software for any |
| purpose on any computer system, and to alter it and redistribute it |
| freely, subject to the following restrictions:</p> |
| |
| <ol> |
| <li>The author is not responsible for the consequences of use of |
| this software, no matter how awful, even if they arise from flaws |
| in it.</li> |
| |
| <li>The origin of this software must not be misrepresented, either |
| by explicit claim or by omission. Since few users ever read |
| sources, credits must appear in the documentation.</li> |
| |
| <li>Altered versions must be plainly marked as such, and must not |
| be misrepresented as being the original software. Since few users |
| ever read sources, credits must appear in the documentation.</li> |
| |
| <li>This notice may not be removed or altered.</li> |
| </ol> |
| </note> |
| |
| <note> |
| <p>For compliance with Mr Darwin's terms: this has been very |
| significantly modified from the free "file" command.</p> |
| |
| <ul> |
| <li>all-in-one file for compilation convenience when moving from |
| one version of Apache to the next.</li> |
| |
| <li>Memory allocation is done through the Apache API's pool |
| structure.</li> |
| |
| <li>All functions have had necessary Apache API request or server |
| structures passed to them where necessary to call other Apache API |
| routines. (<em>i.e.</em>, usually for logging, files, or memory |
| allocation in itself or a called function.)</li> |
| |
| <li>struct magic has been converted from an array to a single-ended |
| linked list because it only grows one record at a time, it's only |
| accessed sequentially, and the Apache API has no equivalent of |
| <code>realloc()</code>.</li> |
| |
| <li>Functions have been changed to get their parameters from the |
| server configuration instead of globals. (It should be reentrant |
| now but has not been tested in a threaded environment.)</li> |
| |
| <li>Places where it used to print results to stdout now saves them |
| in a list where they're used to set the MIME type in the Apache |
| request record.</li> |
| |
| <li>Command-line flags have been removed since they will never be |
| used here.</li> |
| </ul> |
| </note> |
| </section> |
| |
| <directivesynopsis> |
| <name>MimeMagicFile</name> |
| <description>Enable MIME-type determination based on file contents |
| using the specified magic file</description> |
| <syntax>MimeMagicFile <var>file-path</var></syntax> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| |
| <usage> |
| <p>The <directive>MimeMagicFile</directive> directive can be used to |
| enable this module, the default file is distributed at |
| <code>conf/magic</code>. Non-rooted paths are relative to the |
| <directive module="core">ServerRoot</directive>. Virtual hosts will use |
| the same file as the main server unless a more specific setting is |
| used, in which case the more specific setting overrides the main |
| server's file.</p> |
| |
| <example><title>Example</title> |
| MimeMagicFile conf/magic |
| </example> |
| </usage> |
| </directivesynopsis> |
| |
| </modulesynopsis> |
