Mini-vm

A small, register-based virtual machine (bytecode interpreter) in C.

Project maintained by philipaconrad Hosted on GitHub Pages — Theme by mattgraham

A small vm for small projects

Mini-vm is a small (~300 SLOC) bytecode interpreter meant to be used as a starting point for home-made interpreted languages.

How it works:

Each instruction has to be of the same 3-address format.
The VM has a dispatch table of function pointers that all have the same signature.
When the instruction is processed, its Instruction ID serves as an index into that dispatch table.
The instruction runs on the provided data, changes state where required, etc.

How the virtual machine is built:

The interpreter is a register-based machine, with a static number of registers set at compile time. (can't exceed 255, due to bytecode format)
The compiler for the VM is provided by the programmer.
Semantics of instructions are also left up to the programmer.
The VM only covers handling registers and instruction execution. It doesn't even try to address concurrency, stack ops, etc.

Instruction Format:

Each instruction consists of 4 bytes, stored in little-endian byte order:

  0   1   2   3
+---+---+---+---+
| A | B | C | D |
+---+---+---+---+

A - Instruction ID. This is the index of the function in the function table you wish to call.
B - Register #1. (usually the destination register)
C - Register #2. (usually an argument source register)
D - Register #3. (usually an argument source register)

Get:

$ git clone https://github.com/philipaconrad/mini-vm.git

Build:

Linux-likes: If you're using a Linux-like platform (or Cygwin), just use make to build the Mini-vm example program. Use make test to generate sample bytecode and run the example program.
Windows: If you're on a modern Windows platform and have MSVC 2010 installed, just go to the /msvc directory and double click on the .vcxproj file. MSVC should generate a solution file for you, all set up and ready to build.

License

Mini-vm is under the liberal MIT License, so hack away!

Authors and Contributors

Currently, Mini-vm is maintained by @philipaconrad. If you'd like to contribute, just make a pull request.

Support or Contact

Having trouble with Mini-vm? Check out the issues page and we’ll help you sort it out.