LUJE v0.2
=========
Copyright (C) 2013 David Given
2013-10-08
INTRODUCTION
============
Luje is a toy Java virtual machine written in pure Lua. It works by translating
Java bytecode into Lua on-the-fly, and then using Mike Pall's LuaJIT to run the
result. It will run some carefully chosen non-representative microbenchmarks
faster than the OpenJDK will. That's not bad given the whole thing is under
3000 lines of code.
It comes with a rather massacred copy of the Apache Harmony standard library
(some of the things that don't work have been stubbed out).
Right now luje is very, very new and many things don't work --- for example,
not all the Java bytecodes have been implemented (I've been doing them on as
as-needed basis). Plus the native bindings are very immature. However adding
these is really easy; let me know if you need anything.
SETUP
=====
To use Luje you will need:
- an installation of LuaJIT 2, any reasonably recent version; this is
available here:
http://luajit.org/
- a JDK and ant (for building the Java side of things).
I wrote Luje on a Linux machine. I don't see any reason why it wouldn't work on
Windows, given a bit of fiddling, but I'm afraid you're on your own there.
(Let me know if you get it to work.)
Luje itself doesn't need compiling, as it's just a set of Lua scripts, but the
supplied Java library and sample programs do. Build them with:
ant
You may also need to edit the luje shell script and point it at your Lua
package installation, if you keep it somewhere odd. (It's currently set up for
Debian.)
USAGE
=====
To use luje, ensure that the Java main class you want to run is in the bin
directory (the easiest way is to add the Java source file to the lib directory
and run ant), and then invoke it with (for example):
./luje com.cowlark.luje.LocalBench
If all goes according to plan the program will run.
There are some potentially useful command line options, useful for debugging;
try --help.
BUGS
====
Ho ho ho.
- lots of things are barely tested, if at all
- not all bytecodes are implemented, including 'wide'
- Java native bindings are rather minimal
- can't pass arguments into a main function yet
- exceptions don't get stack traces
- no test suite
- conversion from Lua to Java strings and back assume ASCII
- Strings are deadly slow
...and many, many, *many* more.
There's a public bug tracker at http://cowlark.com/luje. Please file bugs. (You
can either do this anonymously or create an account.)
MORE INFORMATION
================
Luje's home is at http://cowlark.com/luje.
Alternatively, you will find a copy of the website (in easier-to-read more-or-
less plain text format) in the doc directory.
THE AUTHOR
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Luje was written by me, David Given. You may contact me at dg@cowlark.com,
or visit my website at http://www.cowlark.com. There may or may not be
anything interesting there.
LICENSING
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Luje is licensed under the Simplified BSD license. See COPYING.luje for the
full text. It also includes big chunks of the Apache Harmony Java run time
library. This is licensed under the Apache 2.0 license; see COPYING.harmony for
the full text.