AbcExplorationLib: Starting an open source project

A couple of months ago I started working on a F# library to read and write ActionScript Byte Code (ABC) files based on the ActionScript Virtual Machine 2 (AVM2) Overview document. I though this was a great opportunity to learn more about both F# and ActionScript.

Although the library is still pretty incomplete, I'll continue the development as an open source project. The project is called AbcExplorationLib and is hosted in CodePlex .

Inspiration for this library comes from excellent bytecode manipulation libraries such as BCEL, ASM, Cecil or System.Reflection.Emit.

When completed this library could be used as part of a complied code analysis tool or as part of the back end of a experimental compiler.

An example of using this library to load a compiled script and print all the names of the opcodes is the following:

let loadedFile =
      using(new BinaryReader(new FileStream("Hello.abc",FileMode.Open))) 
           (fun aInput -> AbcFile.ReadFrom(aInput))


let loadedScript = 
    AvmScript.Create(loadedFile.Scripts.[0],
                     loadedFile.Methods,
                     loadedFile.MethodBodies,
                     loadedFile.ConstantPool);

Array.iter 
   (fun (x:AbcFileInstruction) -> printf "%s\n" x.Name)
   (loadedScript.InitMethod.Body.Value.BodyInfo.GetInstructions())

An example for generating a "Hello world" program:

let abcFileCreator = AbcFileCreator()
let cpCreator = abcFileCreator.ConstantPoolCreator

let instructions =
   [|  GetLocal0 ;
       PushScope ;
       FindPropertyStrict(cpCreator.GetMultiname([|""|],"print"));
       PushString(cpCreator.AddString( "Hola!"));
       CallProperty(cpCreator.GetMultiname([|""|],"print"),1) ;
       CoerceA  ;
       SetLocal_1 ;
       GetLocal1 ;
       ReturnValue ;
       Kill(1);
   |];

let code = ConvertToByteArray(instructions)

let script = 
   AvmScript(
      AvmMethod( "",
                SQualifiedName("*"),
                [||],
                Some (
                  AvmMethodBody(
                      AbcMethodBodyInfo(
                         0, 2, 2, 1, 2,
                         code,
                         [||],[||]
                      ))))); 

abcFileCreator.AddScript(script.ToLowerIr(abcFileCreator))

let fileRep = abcFileCreator.CreateFile() 

using (new BinaryWriter(new FileStream("Hello.abc",FileMode.Create))) (fun f -> fileRep.WriteTo(f))

As you can see this is the part that requires more work! :) .

Future posts will cover the progress of this library.