LuaDecompy/README.md

# LuaDecompy

An experimental Lua 5.1 dump decompiler (typically dumped using `luac -o <out.luac> <script.lua>`).

You will quickly find that only **extremely** simple scripts are decompiled successfully right now. This is an experimental project and not all opcodes are properly handled for now. If you need a real decompiler I would recommend any of the handful of ones that exist already.

## Why?

Lua has a relatively small instruction set (only 38 different opcodes!). This makes it pretty feasible for a weekend decompiler project. (real) Decompilers are extremely complex pieces of software, so being able to write a simpler one helps show the theory without *much* of the headache.

## Example usage

```sh
> cat example.lua && luac5.1 -o example.luac example.lua
local i, x = 10, 2

repeat
    print(i + x)
    i = i - 1
until i < 0
> python main.py example.luac
example.luac

==== [[example.lua's constants]] ====

0: [NUMBER] 10.0
1: [NUMBER] 2.0
2: [STRING] print
3: [NUMBER] 1.0
4: [NUMBER] 0.0

==== [[example.lua's locals]] ====

R[0]: i
R[1]: x

==== [[example.lua's dissassembly]] ====

[  0]      LOADK :   R[0]   K[0]               ; load 10.0 into R[0]
[  1]      LOADK :   R[1]   K[1]               ; load 2.0 into R[1]
[  2]  GETGLOBAL :   R[2]   K[2]               ; move _G["print"] into R[2]
[  3]        ADD :   R[3]   R[0]   R[1]        ; add R[1] to R[0], place into R[3]
[  4]       CALL :      2      2      1        ; 
[  5]        SUB :   R[0]   R[0]   K[3]        ; sub K[3] from R[0], place into R[0]
[  6]         LT :   R[0]   R[0]   K[4]        ; 
[  7]        JMP :   R[0]     -6               ; 
[  8]     RETURN :      0      1      0        ; 

==== [[example.lua's decompiled source]] ====

local i = 10.0
local x = 2.0
repeat
    print((i + x))
    i = (i - 1.0)
until i < 0.0 

```