XobotOS project

XobotOS is a Xamarin research project that explored porting Android 4.0 from Java/Dalvik to C# to explore the performance and memory footprint benefits of C#.

XobotOS is a semi-automated port of the Android 4.0 source code from Java to C#. The automated parts were ported using an improved version of Sharpen that can compile more advanced Java constructs and supports generics. Most of the manual bits of code fall in two categories (a) code to integrate with the host operating system and (b) replace the Java JNI code used to call into C, with the ECMA CLI P/Invoke functionality.

License

The various components of XobotOS are licensed under the same license as their upstream providers. The C# versions of Android is licensed under the terms of the Apache 2 license, while the improved version of Sharpen is licensed under the GPL.

XobotOS Source Code

XobotOS is made up of the following sources:

sharpen:

* Our updated version of Sharpen, see below for changes.

android/generated:

* Fully translated Java to C# code, classes that have been
  translated in this way contain the attribute [Sharpen.Sharpened]

* Empty C# stubs based on the Java declaration: these are
      needed as intermediate steps to get things to build in the
      new C# world.  Classes with empty stubs are decorated with
      the [Sharpen.NakedStub] attribute

android/extra-sources:

* Custom written code that either fine tunes the port,
      provides an alternative optimized version to a class or
      provides a runtime facility.

android/api:

* XML files that describe the translation process from Java to C#.

android/upstream:

* Google's Android 4.0 source code.

libxobotos:

* Glue code to integrate with various Android C++ libraries as
      well as the Linux X11 host that sets up the toplevel window
      and the optional OpenGL context.

* Mostly calls into Skia, Jpeg, OpenGL and ICU libraries.

binaries:

* Libraries to get you started without requiring you to build Skia,
  and other native Android tools.

* Screenshots, videos, and some basic precompiled samples.

monodevelop:

    * Add-in to build native XobotOS applications with MonoDevelop

samples:

* Ported samples to C# using XobotOS

external:

* Native libraries needed to build the unmanaged libxobotos C library

Sharpen

The outcome of this project is a vastly improved Sharpen tool that is able to port very sophisticated and advanced Java codebases from Java to C#. This code lives in the "sharpen" directory.

This modified version of Sharpen can cope with the following enhancements:

* Java generics

* XML-driven translation process

* Type remapping for native Java types to C# types, and supports
  for custom type mappings.

* Support for translating code that does native interop

* Support for generating C's .c and .h files for native glue
      (to assist in P/Invoke support)

* Add attribute-supported translations

* Improved incremental compilation

Documentation on the improved Sharpen engine will be posted in the future so other developers can more easily port Java code to C#.

Support

This code is provided as-is, and we do not offer support for any bits of code here, nor does Xamarin plan on continuing evolving XobotOS at this point.