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Date: Sat, 11 May 2013 09:41:13 +0200
From: Sorin Manolache <sorinm@gmail.com>
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To: modules-dev@httpd.apache.org
Subject: Re: Setting and accessing module specific directory
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On 2013-05-11 08:22, Sindhi Sindhi wrote:
> Thankyou.
> Had one more question. What is the right way of handling this - in which
> location in Apache server directory should I be keeping my filter specific
> files?
>
> As of now the XML and other files that are read by my filter are placed in
> a new folder say "MyFilter" inside "httpd-2.4.4-win64\Apache24\htdocs". Is
> this the right way of doing it?

I think a more "elegant" solution would be to have the location 
configurable.

For that, you define a module-specific configuration directive. (I am 
not familiar with apache 2.4, all my advice is based on apache 2.2, but 
I suppose there is a sufficient degree of backwards compatibility.)

For defining configuration directives, you have to take the following steps:

1. You define one or two callback functions, create_dir_config and/or 
create_server_config. You put their addresses in the corresponing places 
in your module structure. These callback functions are called when 
apache starts up and they should create and return an 
application-specific configuration object that is opaque for apache; it 
sees it as a void pointer.

The server-wide configuration object (created by create_server_config) 
contains configuration data that apply to the whole virtual host.

The directory-wide configuration object (created by create_dir_config) 
contains configuration data that apply to a <Location> or <Directory>.

So, if you have a server with 3 virtual hosts, you have 3 server 
configuration objects per module. However you may have many more 
directory configuration objects, depending on your Locations and 
Directories.

2. You add one entry to the cmds array of your module structure for each 
configuration directive that you want to define. Each cmds array entry 
has a placeholder for your configuration directive-specific callback. 
The callback function is invoked by apache when it parses the 
configuration and it encounters the configuration directive specified by 
your module.

3. You define the configuration directive callback. The callback gets 
the arguments of the configuration directive. What the callback should 
do is to retrieve somehow the configuration object created by the 
callback in step 1 and initialise it with the arguments passed by apache 
(the configuration values).

The directory-wide configuration object is passed in the second argument 
of the configuration callback. You just have to cast the void pointer to 
a pointer to the type of your configuration object.

The server-wide configuration object is retrieved as follows:

ap_get_module_config(params->server->module_config, &my_module)

where params is the cmd_parms argument of the configuration directive 
callback and my_module is the name of your module structure object.

Note that you don't need to use both a server-wide and a directory-wide 
configuration object. The simplest is to use a server-wide. However, a 
directory-wide gives you more configuration flexibility.

The callbacks in steps 1-3 are not called as part of request processing. 
It's more an apache startup and configuration thing. Once apache starts 
processing the requests, it is properly configured and the values of 
your configuration directives are stored in the configuration objects. 
During request processing you'll just have to retrieve these values from 
the configuration objects. This is done is step 4:

4. You retrieve the configuration object of your module from the 
request_rec stucture.

For the server-wide:
MyConf *cnf = (MyConf *)ap_get_module_config(r->server->module_config, 
&my_module);

For the directory-wide:
MyConf *cnf = (MyConf *)ap_get_module_config(r->per_dir_config, &my_module);


> Also, I have downloaded the 64-bit HTTP server from -
>
> http://www.apachelounge.com/download/win64/httpd-2.4.4-win64.zip<http://www.apachelounge.com/download/win64/>
> Is this the right official website to download Apache server?

I think the official builds are downloaded from here:
http://httpd.apache.org/download.cgi

>
>
> On Wed, May 8, 2013 at 11:04 PM, Sorin Manolache <sorinm@gmail.com> wrote:
>
>> On 2013-05-08 17:02, Sindhi Sindhi wrote:
>>
>>> Hi,
>>>
>>> I have written a C++ Apache module that performs filtering of HTML
>>> content.
>>>
>>> There are some XML files which are read by this filter when it does the
>>> filtering. During run-time when this filter is invoked, I'd want the
>>> filter
>>> pick up these XML files and read them. I was thinking these XML files can
>>> be placed in the server location "C:\Program
>>> Files\httpd-2.4.4-win64\**Apache24\htdocs\MyFilter\". where MyFilter
>>> folder
>>> will contain all the XML files needed by my filter. How do I access this
>>> location programatically during run-time when the filter is invoked?
>>>
>>> How can I get the absolute path of the server installation loacation
>>> (C:\Program Files\httpd-2.4.4-win64\**Apache24\htdocs\) so that I can
>>> append
>>> "MyFilter\" to the same to get the location of the XML files?
>>>
>>> I have specified the below in httpd.conf file:
>>> DocumentRoot "C:/Program Files/httpd-2.4.4-win64/**Apache24/htdocs"
>>> ServerRoot "C:/Program Files/httpd-2.4.4-win64/**Apache24"
>>>
>>> The signature of my filter looks like this -
>>> static apr_status_t myHtmlFilter(ap_filter_t *f, apr_bucket_brigade
>>> *pbbIn)
>>>
>>> I will need the document root or server root or any other path variable
>>> that I can access from my filter that will give me the absolute path
>>> "C:/Program Files/httpd-2.4.4-win64/**Apache24"
>>>
>>
>> const char *ap_server_root in http_main.h (apache 2.2. It could be similar
>> in 2.4) contains the ServerRoot.
>>
>> ap_server_root_relative in http_config.h allows you to compose paths
>> relative to the ServerRoot.
>>
>> Sorin
>>
>>
>>> Thanks.
>>>
>>>
>>
>