Conquering DBus

I haven't written in a while because I've been pretty heads down on a project I'm working on. Hopefully, it will be in a shape where it makes sense to share with everyone before too long.

In this project, I needed an RPC system that could have multiple transport and be fully asynchronous (with GAsyncResult, etc). So I took a little time and wrote a crappy little python program that generates the following peices in GObject/C from a simple input format.

• Transport agnostic (currently has DBus backend).
• A client library with lowlevel RPC calls and an object model built on top of the lowlevel calls. Consumer can choose which best fits their use case. (Object model not finished).
• A server implementation (also transport agnostic).
• Fully Asynchronous. Synchronous implementation is built on top of the asynchronous implementation.
• Unit tests (for testing RPC round trips, etc).
• Generated code should be clean to read and debug.
• Tracing support for debugging. (Use -DDISABLE_TRACING to turn off).
• Generate DBus Introspection XML.

Anyway, code is here[1]. There is a sample video below where I generate a mockup service for getting information on "Books" and "Authors". See the Makefile in the outdir directory for how to build things. Keep in mind I have absolutely NO INTENTION of maintaining this. But at minimum, I figured it might serve useful for someone.

So a quick example of the imput format would be like the following. I've removed the header lines for succinctness.

object Book {
    # books are identified by a unique int (string also supported).
    id int

    """
    Document your rpc's with python style docs.  Comments persist into
    the generated code's gtkdoc.
    """
    rpc get_name (out string name)

    """
    Retrieves the book's author.
    """
    rpc get_author (out Author author)
}

object Author {
    id int  
    """
    Retrieves the books by this author.
    """
    rpc get_books (out Book[] books)
}

object Manager {
    # only one of these per application (/org/blah/Project/Manager).
    # might consider this later to simply be the default servce such as
    # (/org/blah/Project).
    singleton

    rpc get_books (out Book[] books)
    rpc get_authors (out Author[] authors)
}

Thats pretty much it. The code is uglier than anything you've ever seen, but at least the generated C is pretty. The code parser/generator is not super resilient or anything. I pretty much hack it to have what I need as I go.

[1] http://github.com/chergert/yosemite

-- Christian Hergert 2010-05-13

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