Received: (qmail 79535 invoked by uid 501); 9 May 2001 09:32:21 -0000
Message-Id: <20010509093221.79525.qmail@apache.org>
Date: 9 May 2001 09:32:21 -0000
From: Jacob Rief <jacob.rief@tiscover.com>
Reply-To: jacob.rief@tiscover.com
To: submit@bugz.apache.org
Subject: additional RewriteMap: dso
X-Send-Pr-Version: 3.110

>Number:         7688
>Category:       mod_rewrite
>Synopsis:       additional RewriteMap: dso
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Quarter:
>Keywords:
>Date-Required:
>Class:          change-request
>Submitter-Id:   apache
>Arrival-Date:   Wed May 09 02:40:04 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     jacob.rief@tiscover.com
>Release:        1.3.19+
>Organization:
apache
>Environment:
Linux 2.2.17 #20 Mon Nov 20 10:20:51 CET 2000 i686 unknown
gcc version 2.96 20000731 (Red Hat Linux 7.0)
>Description:
I would like to release a patch for mod_rewrite to add support for 
an external rewrite-program which links dynamically instead of running
in a seperate process-space such as 
RewriteMap prg:/path/to/external/program

I named this additional RewriteMap "dso" (dynamic shared object). 
It may be used in the same way as an external mapping program. 

This patch is very useful if Your external rewrite-program may hang or may
crash, because it affects only the requesting http-child and not all of the
httpd-precesses inside the server-pool. 
Instead of having an external program communicating with all the
httpd-childs through a single pipe, an external rewrite-dynamic-shared-object
runs inside each httpd's-address space communicating through a singe function
call which I named 'rewrite_lookup_map'. This function takes three parameters,
a const char* for the key, a char* for the mapping result, and the string 
length of the result buffer, currently 2048. The function should return 
zero on failure and one on success. 

Have a look at this example, it just maps lowercase chars to upercase 
and vice versa. 

  ----- example.c ----- 
  int rewrite_lookup_map(const char* key, char* result, int size) 
  { 
          int i; 
          const char* c; 

          i = 0; 
          for (c = key; c; c++) { 
                  if (*c>='A' && *c<='Z') { 
                          result[i] = *c|32; 
                  } else if (*c>='a' && *c<='z') { 
                          result[i] = *c&223; 
                  } else { 
                          result[i] = *c; 
                  } 
                  i++; 
                  if (i==size-1) 
                          return 0; 
          } 
          result[i] = '\0'; 
          return 1; 
  } 
  ----- example.c ----- 

You may build this example program by compiling it as dso: 
> cc -c example -o example.o 
> ld -shared example.o -o example.so 

You may also put the functions _init() and _fini() into 
Your program to initialize it and to cleanup.

Put the following lines into Your httpd.conf: 
  ----- httpd.conf ----- 
  ... 
  RewriteEngine On 
  RewriteMap togglecase dso:/path/to/example.so 
  RewriteRule ^(.*)$ ${togglecase:$1} 
  ... 
  ----- httpd.conf ----- 

and restart the server. This will toggle the case of Your URL's.
This new RewriteMap also avoids the need for a RewriteLock directive 
needed for external rewrite programs.
Please note that apache must be compiled with dso-support enabled to activate
this feature.
>How-To-Repeat:

>Fix:
Download the patch from:
http://homes.tiscover.com/jrief/apache_1.3.19-rewrite-dso.patch
>Release-Note:
>Audit-Trail:
>Unformatted:
 [In order for any reply to be added to the PR database, you need]
 [to include <apbugs@Apache.Org> in the Cc line and make sure the]
 [subject line starts with the report component and number, with ]
 [or without any 'Re:' prefixes (such as "general/1098:" or      ]
 ["Re: general/1098:").  If the subject doesn't match this       ]
 [pattern, your message will be misfiled and ignored.  The       ]
 ["apbugs" address is not added to the Cc line of messages from  ]
 [the database automatically because of the potential for mail   ]
 [loops.  If you do not include this Cc, your reply may be ig-   ]
 [nored unless you are responding to an explicit request from a  ]
 [developer.  Reply only with text; DO NOT SEND ATTACHMENTS!     ]