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<h1 ALIGN="CENTER">Source Re-organisation</h1>
As of 1.3, the Apache source directories have been re-organisated. This
re-organisation is designed to simplify the directory structure,
make it easier to add additional modules, and to give module authors
a way of specifying compile time options or distribute binary
modules.
<h2>Summary of Changes</h2>
The source directory changes are:
<ul>
<li>The non-module source files have moved from <CODE>src</CODE> into
<CODE>src/core</CODE>
</li>
<li>The module source files previously in <CODE>src</CODE> have moved
to <CODE>src/modules/standard</CODE>
</li>
<li>The <CODE>support</CODE> directory is now in <CODE>src/support</CODE>
</li>
</ul>
In addition, the following enhancements have been made:
<ul>
<li>OS abstractions can be added in the <CODE>src/os</CODE> directory.
Currently this contains information for unix, OS/2 and Windows 32
platforms.
</li>
<li><CODE>Configuration</CODE> syntax has been simplified for adding new
modules. Users no longer need to enter the module's structure name.
In addition, new modules can be located anywhere on the
file system, or typically in new or existing directories under
<CODE>src/modules</CODE>.
</li>
<li>Module authors can give simpler instructions for adding their modules
to Apache compilation. They can also now provide compile time information
required by <CODE>Configure</CODE>, such as additional libraries
required.
</li>
<li>Module authors can distribute pre-compiled (.a or .o) versions of their
modules if required, along with a "module definition file" which
contains the information required by <CODE>Configure</CODE>.
</li>
</ul>
<h2>Adding Modules</h2>
Modules are added to Apache by adding a reference tp them in
<CODE>src/Configuration</CODE> then running <CODE>Configure</CODE> and
<CODE>make</CODE>. In earlier version of Apache before 1.3, the
line added to Configuration looked like this:
<PRE>
Module mod_status.o status_module
</PRE>
From 1.3 onwards, the <CODE>AddModule</CODE> line should be used
instead, and typically looks like this:
<PRE>
AddModule modules/standard/mod_status.c
</PRE>
The argument to AddModule is the path, relative to <CODE>src</CODE>, to
the module file's source or object file.
<h2>New Facilities for Module Authors</h2>
In previous releases of Apache, new modules were added to the
<CODE>src</CODE> directory, and if the module required any additional
compilation options (such as libaries) they would have to be added
to <CODE>Configuration</CODE>. Also the user would have to be
told the module's structure name to add on the Module line
of <CODE>Configuration</CODE>.
<P>
From Apache 1.3 onwards, module authors can make use of these new features:
<ul>
<li>Simplified <CODE>Configuration</CODE> command AddModule which only
requires a path to the module source or object file
</li>
<li>If the module requires compile time options (such as extra
libraries) these can be specified in the module file source
or an external "module definition file".
</li>
<li>If a module is distributed as binary (.o or .a) then an external
"module definition file" can also be distributed which gives
the information Configure needs to add the module, such as extra
libraries and the module's structure name.
<li>Module can be installed anyway on the file system, although a directory
under <CODE>src/modules</CODE> is recommended.
</li>
<li>If the module is in its own directory, Apache can automatically
create a Makefile to build the module given a file containing
the module's dependencies.
</li>
</ul>
The rest of this document shows how to package modules for Apache 1.3
and later and what to tell end-users of the module.
<h3>Building a simple source distibution</h3>
Consider a simple add-on module, distributed as a single file. For
example, say it is called mod_demo.c. The archive for this module
should consist of two files, in a suitable directory name. For
example:
<ul>
<li>mod_demo/mod_demo.c
<li>mod_demo/Makefile.tmpl
</ul>
(Of course end-user instructions, README's etc can also be supplied in
the archive). The end user should be told to extract this archive in
the <CODE>src/modules</CODE> directory of their Apache source
tree. This will create a new directory
<CODE>src/modules/mod_demo</CODE>. Then they need to add the following
line to the <CODE>Configuration</CODE> file:
<pre>
AddModule modules/mod_demo/mod_demo
</pre>
then run <CODE>Configure</CODE> and <CODE>make</CODE> as normal.
<P>
The <CODE>mod_demo/Makefile.tmpl</CODE> should contain the dependencies
of the module source. For example, a simple module which just interfaces to
some standard Apache module API functions might look this this:
<PRE>
mod_demo.o: mod_demo.c $(INCDIR)/httpd.h $(INCDIR)/http_protocol.h
</PRE>
When the user runs <CODE>Configure</CODE> Apache will create a full
makefile to build this module. If this module also requires
some additional built-time options to be given, such as libaries,
see the next section.
<P>
If the module also comes with header files, these can be added to the
archive. If the module consists of multiple source files it can be
built into a library file using a supplied makefile. In this case,
distribute the makefile as <CODE>mod_demo/Makefile</CODE> and <b>do
not</b> include a <CODE>mod_demo/Makefile.tmpl</CODE>. If
<CODE>Configure</CODE> see a <CODE>Makefile.tmpl</CODE> it assmes it
is safe to overwrite any existing<CODE>Makefile</CODE>.
<P>
See the Apache <CODE>src/modules/standard</CODE> for an example of a
module directory where the makeifle is create automatically from a
Makefile.tmpl file (note also that this directory also shows how to
distributed multiple modules in a single directory). See
<CODE>src/modules/proxy</CODE> and <CODE>src/modules/example</CODE>
for examples of modules build using custom makefiles (to build a
library and an object file, respectively).
<h3>Adding Compile time Information</h3>
Apache source files (or module definition files, see below) can
contain information used by <CODE>Configure</CODE> to add compile-time
options such as additional libraries. For example, if mod_demo in the
example above also requires that Apache be linked against a DBM
library, then the following text could be inserted into the mod_demo.c
source:
<PRE>
/*
* Module definition information - the part between the -START and -END
* lines below is used by Configure. This could be stored in a separate
* instead.
*
* MODULE-DEFINITION-START
* Name: demo_module
* ConfigStart
LIBS="$LIBS $DBM_LIB"
if [ "X$DBM_LIB" != "X" ]; then
echo " + using $DBM_LIB for mod_demo"
fi
* ConfigEnd
* MODULE-DEFINITION-END
*/
</PRE>
Note that this is contained inside a C language comment to hide it
from the compiler. Anything between the lines which contains
<CODE>MODULE-DEFINITION-START</CODE> and
<CODE>MODULE-DEFINITION-END</CODE> is used by <CODE>Configure</CODE>.
The <CODE>Name:</CODE> line gives the module's structure name. This is
not really necessary in this case since if not present
<CODE>Configure</CODE> will guess at a name based on the filename
(e.g. given "mod_demo" it will remove the leading "mod_" and append
"_module" to get a structure name. This works with all modules
distributed with Apache).
<P>
The lines between <CODE>ConfigStart</CODE> and <CODE>ConfigEnd</CODE>
as executed by <CODE>Configure</CODE> and can be used to add
compile-time options and libraries. In this case it adds the DBM
library (from $DBM_LIB) to the standard compilation libraries ($LIB)
and displays a message.
<P>
See the default distribution's mod_auth_dbm.c for an example of
an embedded module definition.
<h3>Module Definition Information for Binary Distribitions</h3>
If the module is to be distributed as binary (object or libary) rather
than source, it is not possible to add the module definition
information to the source file. In this case it can be placed in a
separate file which has the same base name as the object or libary
file, but with a <CODE>.module</CODE> extension. So, for example, if
the distributed module object file is mod_demo.o, the module
definition file should be called mod_demo.module. It contains the same
information as above, but does not need to be inside a C comment or
delimited with <CODE>MODULE-DEFINITION-START</CODE> etc. For example:
<PRE>
Name: demo_module
ConfigStart
LIBS="$LIBS $DBM_LIB"
if [ "X$DBM_LIB" != "X" ]; then
echo " + using $DBM_LIB for mod_demo"
fi
ConfigEnd
</PRE>
See the default distribution's mod_auth_db.module for an example of
an separate module definition file.
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