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Saturday, April 21, 2012

User Modules

I've recently committed support for user modules in Qore; this will allow the language to be extended in an organized and predictable way with Qore-language code.

Before this was only possible with modules written in C++.

The current documentation for user modules is online here: http://qore.org/manual/current/lang/html/qore_modules.html#user_modules (note: edited to reflect a perma-link for the user module documentation in the latest qore docs)

User modules have the following features:
  • code embedding safety: modules work with Qore's functional domain permission/protection framework so that embedded code can only use modules that use authorized functionality
  • encapsulation: only symbols marked as public are exported; everything else is private to the module
  • uniqueness: multiple pieces (source files) can "require" a module safely - also when embedding Qore code, when multiple Programs use a module, there is only one copy of the module and of its private data (single global state)
Note that also there has been a nearly complete rewrite of the namespace code and handling to facilitate user modules - particularly to enable public and private symbols in modules. For example, now global variables are also contained in namespaces (hence it's possible to have more than 1 copy of a global variable with the same name in different namespaces).

The next step will be to integrate a separate program called "qdx" which converts Qore code to a c++-like format for doxygen parsing so that doxygen documentation can be generated from Qore modules and those can be integrated into Qore's reference documentation (at least for the modules that will be shipped with Qore - this will be the start of Qore's Qore-language runtime library).

I have already added a couple of user modules to the Qore source in svn (HttpServer.qm and Smtp.qm) and updated the build and packaging code accordingly.

The new directory location for the runtime library is the Qore version string as a subdirectory of "qore-modules" (where binary/c++ modules are installed). For example on UNIX this might be:

/usr/lib64/qore-modules/0.8.4

This directory is automatically added to the QORE_MODULE_DIR search path.

I hope this will enable more collaboration to be made on Qore and of course for the language to be more transparent and useful for more people.