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.