A small, register-based virtual machine (bytecode interpreter) in C.
Each bytecode instruction is 4 bytes long.
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)
Instead of the usual switch/case-based architecture most bytecode interpreters use, I chose to go with a table of function pointers whose indices correspond with particular instruction IDs.
An interpreter can be initialized by calling initVMContext() and supplying
the appropriate parameters.
The interpreter's state has to be advanced one instruction at a time by
by calling stepVMContext() repeatedly. In the example programs, this is
typically done with a simple while loop.
Termination is not accounted for by default. Adding a custom halt instruction or some sort of status register are both plausible solutions.
- On *nix platforms, just type
maketo build mini-vm as a static library. To build the examples, just typemake testin each example's directory. - For Windows: An MSVC 2010 Project file is provided under
/msvc. Double click on it to generate a solution file.
- Look under the
/examplesfolder to see examples of mini-vm in action. - Also worth reading: the project's site. The bytecode format and the structure of the VM are explained here.
Copyright (c) 2013 Philip Conrad. All rights reserved.
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