dgaudet 97/09/11 11:50:35
Modified: src Configuration.tmpl
Added: htdocs/manual/mod mod_speling.html
src/modules/standard mod_speling.c
Log:
Add in mod_speling.
Submitted by: Martin Kraemer, Alexei Kosut
Reviewed by: various
Revision Changes Path
1.1 apachen/htdocs/manual/mod/mod_speling.html
Index: mod_speling.html
===================================================================
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<TITLE>Apache module mod_speling</TITLE>
</HEAD>
<!-- Background white, links blue (unvisited), navy (visited), red (active)
-->
<BODY
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#000080"
ALINK="#FF0000"
>
<!--#include virtual="header.html" -->
<H1 ALIGN="CENTER">Module mod_speling</H1>
<P>
This module is contained in the <code>mod_speling.c</code> file,
and is <strong>not</strong> compiled in by default.
It attemps to correct mispellings of
URLs that users might have entered, by ignoring capitalization
and by allowing up to one misspelling.<br>
This catches the majority of misspelled requests. An automatic
"spelling corrected" redirection is returned if only one matching
document was found, and a list of matches is returned if more than
one document with a sufficiently similar name is found.
</P>
<h2>Summary</h2>
<p>
Requests to documents sometimes cannot be served by the core apache
server because the request was misspelled or miscapitalized. This
module addresses this problem by trying to find a matching document,
even after all other modules gave up. It does its work by comparing
each document name in the requested directory against the requested
document name <STRONG>without regard to case</STRONG>, and allowing
<STRONG>up to one misspelling</STRONG> (character insertion / omission
/ transposition or wrong character). A list is built with all document
names which were matched using this strategy.
</p>
<p>
If, after scanning the directory,
<ul>
<li>no matching document was found, Apache will proceed as usual
and return a "document not found" error.
<li>only one document is found that "almost" matches the request,
then it is returned in the form of a redirection response.
<li>more than one document with a close match was found, then
the list of the matches is returned to the client, and the client
can select the correct candidate.
</ul>
</p>
<h2>Directives</h2>
<menu>
<li><A HREF="#checkspelling">CheckSpelling</A>
</menu>
<HR> <!-- the HR is part of the directive description -->
<A name="checkspelling"><h2>CheckSpelling</h2></A>
<!--%plaintext <?INDEX {\tt CheckSpelling} directive> -->
<strong>Syntax:</strong> CheckSpelling <em>on/off</em><br>
<strong>Default:</strong> <code>CheckSpelling Off</code><br>
<Strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_speling<br>
<strong>Compatibility:</strong> CheckSpelling was available as a separately
available module for Apache 1.1, but was limited to miscapitalizations.
As of Apache 1.3, it is part of the apache distribution<!-- or:
available as a separate module-->.<p>
This directive enables or disables the spelling module. When enabled,
keep in mind that
<UL>
<LI>the directory scan which is necessary for the spelling
correction will have an impact on the server's performance
when many spelling corrections have to be performed at the same time.
<LI>the document trees should not contain sensitive files which could
be matched inadvertedly, by a spelling "correction".
<LI>the module is unable to correct misspelled user names
(as in <code>http://my.host/~apahce/</code>), just file names or
directory names.
</UL>
<!--#include virtual="footer.html" -->
</BODY>
</HTML>
1.76 +9 -0 apachen/src/Configuration.tmpl
Index: Configuration.tmpl
===================================================================
RCS file: /export/home/cvs/apachen/src/Configuration.tmpl,v
retrieving revision 1.75
retrieving revision 1.76
diff -u -r1.75 -r1.76
--- Configuration.tmpl 1997/08/31 22:36:22 1.75
+++ Configuration.tmpl 1997/09/11 18:50:31 1.76
@@ -211,6 +211,15 @@
##
## URL translation modules.
##
+
+## The Speling module attemps to correct mispellings of URLs that
+## users might have entered, namely by checking capitalizations
+## or by allowing up to one misspelling (character insertion / omission /
+## transposition/typo). This catches the majority of misspelled requests.
+## If it finds a match, a "spelling corrected" redirection is returned.
+
+# AddModule modules/standard/mod_speling.o
+
## The UserDir module for selecting resource directories by user name
## and a common prefix, e.g., /~<user> , /usr/web/<user> , etc.
1.1 apachen/src/modules/standard/mod_speling.c
Index: mod_speling.c
===================================================================
#define WANT_BASENAME_MATCH
/* ====================================================================
* Copyright (c) 1996,1997 The Apache Group. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the Apache Group
* for use in the Apache HTTP server project (http://www.apache.org/)."
*
* 4. The names "Apache Server" and "Apache Group" must not be used to
* endorse or promote products derived from this software without
* prior written permission.
*
* 5. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the Apache Group
* for use in the Apache HTTP server project (http://www.apache.org/)."
*
* THIS SOFTWARE IS PROVIDED BY THE APACHE GROUP ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE APACHE GROUP OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Group and was originally based
* on public domain software written at the National Center for
* Supercomputing Applications, University of Illinois, Urbana-Champaign.
* For more information on the Apache Group and the Apache HTTP server
* project, please see <http://www.apache.org/>.
*
*/
#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
/* mod_speling.c - by Alexei Kosut <[EMAIL PROTECTED]> June, 1996
*
* This module is transparent, and simple. It attemps to correct
* mispellings of URLs that users might have entered, namely by checking
* capitalizations. If it finds a match, it sends a redirect.
*
* 08-Aug-1997 <[EMAIL PROTECTED]>
* o Upgraded module interface to apache_1.3a2-dev API (more NULL's in
speling_module).
* o Integrated tcsh's "spelling correction" routine which allows one
* misspelling (character insertion/omission/typo/transposition).
* Rewrote it to ignore case as well. This ought to catch the majority
* of misspelled requests.
* o Commented out the second pass where files' suffixes are stripped.
* Given the better hit rate of the first pass, this rather ugly
* (request index.html, receive index.db ?!?!) solution can be
* omitted.
* o wrote a "kind of" html page for mod_speling
*
* Activate it with "CheckSpelling On"
*/
module speling_module;
/* We use the "unconventional" mod_userdir approach here. And heck,
* here it's just one int!
*/
static void *create_speling_config(pool * dummy, server_rec * s)
{
return (void *) 0;
}
static const char *set_speling(cmd_parms * cmd, void *dummy, int arg)
{
void *server_conf = cmd->server->module_config;
set_module_config(server_conf, &speling_module, (void *) arg);
return NULL;
}
command_rec speling_cmds[] =
{
{"CheckSpelling", set_speling, NULL, RSRC_CONF, FLAG,
"whether or not to fix miscapitalized/misspelled requests"},
{NULL}
};
typedef enum {
SP_IDENTICAL = 0,
SP_MISCAPITALIZED = 1,
SP_TRANSPOSITION = 2,
SP_MISSINGCHAR = 3,
SP_EXTRACHAR = 4,
SP_SIMPLETYPO = 5,
SP_VERYDIFFERENT = 6
} sp_reason;
static const char *sp_reason_str[] =
{
"identical",
"miscapitalized",
"transposed characters",
"character missing",
"extra character",
"mistyped character",
"common basename",
};
typedef struct {
const char *name;
sp_reason quality;
} misspelled_file;
/*
* spdist() is taken from Kernighan & Pike,
* _The_UNIX_Programming_Environment_
* and adapted somewhat to correspond better to psychological reality.
* (Note the changes to the return values)
*
* According to Pollock and Zamora, CACM April 1984 (V. 27, No. 4),
* page 363, the correct order for this is:
* OMISSION = TRANSPOSITION > INSERTION > SUBSTITUTION
* thus, it was exactly backwards in the old version. -- PWP
*
* This routine was taken out of tcsh's spelling correction code
* (tcsh-6.07.04) and re-converted to apache data types ("char" type
* instead of tcsh's NLS'ed "Char"). Plus it now ignores the case
* during comparisons, so is a "approximate strcasecmp()".
* NOTE that is still allows only _one_ real "typo",
* it does NOT try to correct multiple errors.
*/
static sp_reason spdist(const char *s, const char *t)
{
for (; tolower(*s) == tolower(*t); t++, s++)
if (*t == '\0')
return SP_MISCAPITALIZED; /* exact match (sans case) */
if (*s) {
if (*t) {
if (s[1] && t[1] && tolower(*s) == tolower(t[1]) &&
tolower(*t) == tolower(s[1]) && strcasecmp(s + 2, t + 2) == 0)
return SP_TRANSPOSITION; /* transposition */
if (strcasecmp(s + 1, t + 1) == 0)
return SP_SIMPLETYPO; /* 1 char mismatch */
}
if (strcasecmp(s + 1, t) == 0)
return SP_EXTRACHAR; /* extra character */
}
if (*t && strcasecmp(s, t + 1) == 0)
return SP_MISSINGCHAR; /* missing character */
return SP_VERYDIFFERENT; /* distance too large to fix. */
}
static int sort_by_quality(const void *left, const void *rite)
{
return (int) (((misspelled_file *) left)->quality)
- (int) (((misspelled_file *) rite)->quality);
}
static int check_speling(request_rec * r)
{
void *server_conf = r->server->module_config;
char *good, *bad, *postgood, *url;
int filoc, dotloc, urlen, pglen;
DIR *dirp;
struct DIR_TYPE *dir_entry;
array_header *candidates = NULL;
if (!(int) get_module_config(server_conf, &speling_module))
return DECLINED;
/* We only want to worry about GETs */
if (r->method_number != M_GET)
return DECLINED;
/* We've already got a file of some kind or another */
if (r->proxyreq || (r->finfo.st_mode != 0))
return DECLINED;
/* This is a sub request - don't mess with it */
if (r->main)
return DECLINED;
/* The request should end up looking like this:
* r->uri: /correct-url/mispelling/more
* r->filename: /correct-file/mispelling r->path_info: /more
*
* So we do this in steps. First break r->filename into two peices
*/
filoc = rind(r->filename, '/');
if (filoc == -1)
return DECLINED;
/* good = /correct-file */
good = pstrndup(r->pool, r->filename, filoc);
/* bad = mispelling */
bad = pstrdup(r->pool, r->filename + filoc + 1);
/* postgood = mispelling/more */
postgood = pstrcat(r->pool, bad, r->path_info, NULL);
urlen = strlen(r->uri);
pglen = strlen(postgood);
/* Check to see if the URL pieces add up */
if (strcmp(postgood, r->uri + (urlen - pglen)))
return DECLINED;
/* url = /correct-url */
url = pstrndup(r->pool, r->uri, (urlen - pglen));
/* Now open the directory and do ourselves a check... */
dirp = opendir(good);
if (dirp == NULL) /* Oops, not a directory... */
return DECLINED;
candidates = make_array(r->pool, 2, sizeof(misspelled_file));
dotloc = ind(bad, '.');
if (dotloc == -1)
dotloc = strlen(bad);
while ((dir_entry = readdir(dirp))) {
sp_reason q;
/* If we end up with a "fixed" URL which is identical to the
* requested one, we must have found a broken symlink or some such.
* Do _not_ try to redirect this, it causes a loop!
*/
if (strcmp(bad, dir_entry->d_name) == 0)
{
closedir(dirp);
return OK;
}
/*
* miscapitalization errors are checked first
* (like, e.g., lower case file, upper case request)
*/
else if (strcasecmp(bad, dir_entry->d_name) == 0) {
misspelled_file *sp_new = (misspelled_file *)
push_array(candidates);
sp_new->name = pstrdup(r->pool, dir_entry->d_name);
sp_new->quality = SP_MISCAPITALIZED;
}
/*
* simple typing errors are checked next
* (like, e.g., missing/extra/transposed char)
*/
else if ((q = spdist(bad, dir_entry->d_name)) != SP_VERYDIFFERENT) {
misspelled_file *sp_new = (misspelled_file *)
push_array(candidates);
sp_new->name = pstrdup(r->pool, dir_entry->d_name);
sp_new->quality = q;
}
/* The spdist() should have found the majority of the misspelled
requests.
* it is of questionable use to continue looking for files with the same
* base name, but potentially of totally wrong type (index.html <->
index.db)
* I would propose to not set the WANT_BASENAME_MATCH define.
* 08-Aug-1997 <[EMAIL PROTECTED]>
*
* However, Alexei replied giving some reasons to add it anyway:
* > Oh, by the way, I remembered why having the
* > extension-stripping-and-matching stuff is a good idea:
* >
* > If you're using MultiViews, and have a file named foobar.html,
which you
* > refer to as "foobar", and someone tried to access "Foobar",
mod_speling
* > won't find it, because it won't find anything matching that
* > spelling. With the extension-munging, it would locate
"foobar.html". Not
* > perfect, but I ran into that problem when I first wrote the module.
*/
else {
#ifdef WANT_BASENAME_MATCH
/* Okay... we didn't find anything. Now we take out the hard-core
* power tools. There are several cases here. Someone might have
* entered a wrong extension (.htm instead of .html or vice versa)
* or the document could be negotiated. At any rate, now we just
compare
* stuff before the first dot. If it matches, we figure we got us a
* match. This can result in wrong things if there are files of
* different content types but the same prefix (e.g. foo.gif and
foo.html)
* This code will pick the first one it finds. Better than a Not
Found,
* though.
*/
int entloc = ind(dir_entry->d_name, '.');
if (entloc == -1)
entloc = strlen(dir_entry->d_name);
if ((dotloc == entloc)
&& !strncasecmp(bad, dir_entry->d_name, dotloc)) {
misspelled_file *sp_new = (misspelled_file *)
push_array(candidates);
sp_new->name = pstrdup(r->pool, dir_entry->d_name);
sp_new->quality = SP_VERYDIFFERENT;
}
#endif
}
}
closedir(dirp);
if (candidates->nelts != 0) {
/* Wow... we found us a mispelling. Construct a fixed url */
char *nuri, *ref;
misspelled_file *variant = (misspelled_file *) candidates->elts;
int i;
ref = table_get(r->headers_in, "Referer");
qsort((void *) candidates->elts, candidates->nelts,
sizeof(misspelled_file), sort_by_quality);
/*
* Conditions for immediate redirection:
* a) the first candidate was not found by stripping the suffix
* AND b) there exists only one candidate OR the best match is not
ambigous
*
* Otherwise, a "[300] Multiple Choices" list with the variants is
returned.
*/
if (variant[0].quality != SP_VERYDIFFERENT &&
(candidates->nelts == 1 || variant[0].quality !=
variant[1].quality)) {
nuri = pstrcat(r->pool, url, variant[0].name,
r->path_info, NULL);
table_set(r->headers_out, "Location",
construct_url(r->pool, nuri, r->server));
aplog_error(APLOG_MARK, APLOG_ERR, r->server,
ref ? "Fixed spelling: %s to %s from %s"
: "Fixed spelling: %s to %s",
r->uri, nuri, ref);
return HTTP_MOVED_PERMANENTLY;
}
/*
* Otherwise, a "[300] Multiple Choices" list with the variants is
returned.
*/
else {
char *t;
pool *pool;
table *notes;
if (r->main == NULL) {
pool = r->pool;
notes = r->notes;
}
else {
pool = r->main->pool;
notes = r->main->notes;
}
/* Generate the reponse text. */
t = pstrcat(pool, "The document name you requested (<code>",
r->uri, "</code>) could not be found on this server.\n"
"However, we found documents with names similar to the
one you requested.<p>"
"Available documents:\n<ul>\n", NULL);
for (i = 0; i < candidates->nelts; ++i) {
/* The format isn't very neat... */
t = pstrcat(pool, t, "<li><a href=\"", variant[i].name, "\">",
variant[i].name, "</a> (",
sp_reason_str[(int) (variant[i].quality)], ")\n",
NULL);
/* when we have printed the "close matches" and there
* are more "distant matches" (matched by stripping the
* suffix), then we insert an additional separator text
* to suggest that the user LOOK CLOSELY whether these
* are really the files she wanted.
*/
if (i > 0 && i < candidates->nelts - 1
&& variant[i].quality != SP_VERYDIFFERENT
&& variant[i + 1].quality == SP_VERYDIFFERENT) {
t = pstrcat(pool, t, "</ul>\nFurthermore, the following
related documents were found:\n<ul>\n", NULL);
}
}
t = pstrcat(pool, t, "</ul>\n", NULL);
/* If we know there was a referring page, add a note: */
if (ref != NULL)
t = pstrcat(pool, t, "Please consider informing the owner of
the <a href=\"",
ref, "\">referring page</a> about the broken link.\n", NULL);
/* Pass our table to http_protocol.c (see mod_negotiation): */
table_set(notes, "variant-list", t);
aplog_error(APLOG_MARK, APLOG_WARNING, r->server,
ref ? "Spelling fix: %s: %d candidates from %s"
: "Spelling fix: %s: %d candidates",
r->uri, candidates->nelts, ref);
return HTTP_MULTIPLE_CHOICES;
}
}
return OK;
}
module MODULE_VAR_EXPORT speling_module = {
STANDARD_MODULE_STUFF,
NULL, /* initializer */
NULL, /* create per-dir config */
NULL, /* merge per-dir config */
create_speling_config, /* server config */
NULL, /* merge server config */
speling_cmds, /* command table */
NULL, /* handlers */
NULL, /* filename translation */
NULL, /* check_user_id */
NULL, /* check auth */
NULL, /* check access */
NULL, /* type_checker */
check_speling, /* fixups */
NULL, /* logger */
NULL, /* header parser */
NULL, /* child_init */
NULL, /* child_exit */
NULL /* post read-request */
};
