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| <modulesynopsis> |
| |
| <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 MIME type of files in the same |
| way the Unix file(1) 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. To assure that mod_mime gets first try at determining |
| a file's MIME type, be sure to list mod_mime_magic |
| <strong>before</strong> mod_mime in the configuration.</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><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 "#". The remaining lines are parsed for the |
| following columns:</p> |
| |
| <table border="1"> |
| <tr valign="top"> |
| <th>Column</th> |
| |
| <th>Description</th> |
| </tr> |
| |
| <tr valign="top"> |
| <td>1</td> |
| |
| <td>byte number to begin checking from<br /> |
| ">" indicates a dependency upon the previous non-">" |
| line</td> |
| </tr> |
| |
| <tr valign="top"> |
| <td>2</td> |
| |
| <td> |
| type of data to match |
| |
| <table border="1"> |
| <tr> |
| <td>byte</td> |
| |
| <td>single character</td> |
| </tr> |
| |
| <tr> |
| <td>short</td> |
| |
| <td>machine-order 16-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>long</td> |
| |
| <td>machine-order 32-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>string</td> |
| |
| <td>arbitrary-length string</td> |
| </tr> |
| |
| <tr> |
| <td>date</td> |
| |
| <td>long integer date (seconds since Unix |
| epoch/1970)</td> |
| </tr> |
| |
| <tr> |
| <td>beshort</td> |
| |
| <td>big-endian 16-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>belong</td> |
| |
| <td>big-endian 32-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>bedate</td> |
| |
| <td>big-endian 32-bit integer date</td> |
| </tr> |
| |
| <tr> |
| <td>leshort</td> |
| |
| <td>little-endian 16-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>lelong</td> |
| |
| <td>little-endian 32-bit integer</td> |
| </tr> |
| |
| <tr> |
| <td>ledate</td> |
| |
| <td>little-endian 32-bit integer date</td> |
| </tr> |
| </table> |
| </td> |
| </tr> |
| |
| <tr valign="top"> |
| <td>3</td> |
| |
| <td>contents of data to match</td> |
| </tr> |
| |
| <tr valign="top"> |
| <td>4</td> |
| |
| <td>MIME type if matched</td> |
| </tr> |
| |
| <tr valign="top"> |
| <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 "*.doc" 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><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 file(1) 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> |
| |
| <p>When compiling an Apache server, this module should be at or |
| near the top of the list of modules in the Configuration file. |
| The modules are listed in increasing priority so that will mean |
| this one is used only as a last resort, just like it was |
| designed to.</p> |
| |
| </section> |
| |
| <section id="notes"><title>Notes</title> |
| |
| <p>The following notes apply to the mod_mime_magic module and are |
| included here for compliance with contributors' copyright |
| restrictions that require their acknowledgment. </p> |
| <pre> |
| /* |
| * mod_mime_magic: MIME type lookup via file magic numbers |
| * Copyright (c) 1996-1997 Cisco Systems, Inc. |
| * |
| * 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. |
| * |
| * 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. |
| * --------------------------------------------------------------------------- |
| * - Copyright (c) Ian F. Darwin, 1987. Written by Ian F. Darwin. |
| * |
| * This software is not subject to any license of the American Telephone and |
| * Telegraph Company or of the Regents of the University of California. |
| * |
| * 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: |
| * |
| * 1. 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. |
| * |
| * 2. 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. |
| * |
| * 3. 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. |
| * |
| * 4. This notice may not be removed or altered. |
| * ------------------------------------------------------------------------- |
| * |
| * For compliance with Mr Darwin's terms: this has been very significantly |
| * modified from the free "file" command. |
| * - all-in-one file for compilation convenience when moving from one |
| * version of Apache to the next. |
| * - Memory allocation is done through the Apache API's pool structure. |
| * - 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.) |
| * - 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 realloc(). |
| * - 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.) |
| * - 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. |
| * - Command-line flags have been removed since they will never be used here. |
| * |
| */ |
| </pre> |
| </section> |
| |
| <directivesynopsis> |
| <name>MimeMagicFile</name> |
| <description>Enable MIME-type determination based on file contents |
| using the specified magic file</description> |
| <syntax>MimeMagicFile <em>file-path</em></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 |
| ServerRoot. 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> |
| </usage> |
| </directivesynopsis> |
| </modulesynopsis> |
| |
