Obzcure Virtual Machine

Java virtual machine made in Java

THIS IS NOT PRODUCTION SAFE - WORK IN PROGRESS!

• Use at your own risk.
• Requires Java 17 (with preview features)

java --enable-preview -jar ObzcureVM.jar
"path/to/java17" --enable-preview -jar ObzcureVM.jar -i in.jar -o out.jar -fp -rf -rm -sd
"C:\Program Files\Java\graalvm-ce-java17-21.3.0\bin\java.exe" --enable-preview -jar ObzcureVM.jar -i in.jar -o out.jar -fp -rf -rm -sd

The virtualized output jar also now requires Java 17 (with preview features)

Usage:
 -fp,--forcePublic      Make every field and method public (accessible
                        from everywhere)
 -i,--input <input>     Input jar file
 -o,--output <output>   Output jar file
 -rf,--removeFinal      Force virtualization of final fields (removes
                        final access)
 -rm,--rndMeow          Random cats.meow filename
 -sd,--skipDebug        Remove debugging information from all classes

Before

After

Example timings:

Virtualized output file:

• 5458 ms
• 5011 ms
• 4947 ms
• 4873 ms
• 4937 ms

Original input file:

• 53 ms
• 18 ms
• 21 ms
• 12 ms
• 9 ms

As you can see from these 5 test runs, the virtualized version of a jar is up to 606 times slower than the original jar.
This is a worst case scenario, where a huge jar was fully virtualized including lots of nested loops.
If you only virtualize a few specific methods, it shouldn't be much slower than the original.