Programming, Software and Code

A few days ago I started a new project that I am provisionally calling Parrot# (“Parrot-Sharp”). This new project provides bindings for Parrot in C# or other .NET code using Parrot’s new embedding API.

A while back I showed an example on this blog of a very short toy program, written in C#, which embedded Parrot and printed out a short “hello world” message. I knew, after having done that example, that I would be able to get this new project working without too much trouble. The big saving grace here is that the API works almost exclusively on PMC, STRING, and simple types, which makes wrapping the function calls very easy. I wrap the low-level pointers up in custom C# proxy types that include calls to the native functions in libparrot.

Tonight, I have an example program that runs. Here’s the C# code of the test executable:

using System;

namespace ParrotTest
{
    class MainClass
    {
        public static void Main (string[] args)
        {
            string exename = AppDomain.CurrentDomain.FriendlyName;
            if (args.Length <= 0) {
                Console.WriteLine("No PBC file specified");
                return;
            }
            string pbcfile = args[0];
            string[] pbcargs = new string[args.Length - 1];
            for (int i = 1; i < args.Length; i++)
                pbcargs[i - 1] = args[i];
            Parrot.Parrot parrot = new Parrot.Parrot(exename);
            Parrot.Parrot_PMC pbc = parrot.LoadBytecodeFile(pbcfile);
            Parrot.Parrot_PMC mainargs = parrot.PmcNull;
            parrot.RunBytecode(pbc, mainargs);
        }
    }
}

It’s a simple wrapper program that runs a PBC file. I write a simple PIR file:

$> cat test.pir
.sub main :main
    say "Hello from a PIR file!"
.end

Now, I compile it:

$> parrot -o test.pbc test.pir

…And run it with my new Program:

$> .ParrotSharp.exe test.pbc
Hello from a PIR file!

I actually have a lot more functionality written than what is exercised here, but I’m having a few problems with MonoDevelop and it’s not finding some of the classes and methods I have written. Once I get some of these thing working It will be a lot more functional.

I’ll write more about this project as it matures, but it is currently functional enough to execute Parrot bytecode, and I feel like that is a milestone worth reporting. I also have exceptions working more or less properly (I’ve even used my implementation of exceptions here to find a bug in the embed_api2 branch), and a few other things.

In order to completely replace the Parrot executable I would have to implement wrappers for IMCC, and frankly I just don’t want to do that. For now the ParrotSharp library is going to provide all other functionality for working with PMCs, STRINGs, and bytecode. Eventually I’m going to put together some unit tests too.

Parrot’s new embedding API has it’s first consumer, I’m excited to see what other kinds of things people can do with it.