11.1. Implementing Configuration Directives in C
The C-language API allows modules to install their own configuration directives. The directives' syntax and usage information are defined in a command_rec data structure and processed by directive handler callback routines defined within the module.
Whereas the configuration API is optional in Perl modules due to the catchall PerlSetVar directive, C-language programmers don't have this luxury. You'll have to create custom configuration directives in order to write any module that requires runtime configuration information.
Modules are responsible for managing their own configuration data. There are two general types of configuration data: data that apply to a particular server or virtual host and data that apply to a directory or URI. A module can maintain both server-specific and directory-specific configuration information or just one or the other, depending on its needs. Because there may be dozens of virtual hosts and hundreds of directories, the Apache API allows modules to juggle thousands of configuration records. During configuration file processing, Apache will call your module's configuration allocation and processing routines at the right time and in the right order to create the configuration data. Then, at request time, Apache will choose the correct configuration record to return to your handler when the handler requests it.
The work of creating and maintaining configuration records is done in several ...