uLua

Lua compiler and iterpreter to run on microcontroller (AVR 8 bit)

About

uLua aimed to run Lua scripts on microcontrollers with very limited resources, like RAM. uLua should work on microcontrollers with RAM >= 1k. Second thing which uLua should achieve is fast code interpreter. Goal is 1 Million Lua instructions on 10 MIPS (10 MHz for AVR). Usage

luac.exe -s -o alltest.luc alltest.lua
ChunkSpy.lua alltest.luc alltest.lua -o alltest.lst
uLuaPC.exe alltest.luc

ChunkSpy.lua - optional. This script used to generate listing file from compiled luc file. Features

Currenly support:

function calls global consts global and local variables math operations for loops native functions (like print()) closures with upvalues garbage collector

Following code could be executed by uLua.

--load nil test
function loadtest()
        local a,b,c,d,e = nil,nil,0
        local aa,bb = true,false
        print(a,b,c)
        print(aa,bb)
end
loadtest()

-- for loop test
for i = 1, 3, 1 do
        print(i)
end 

for i = 3, 1, -1 do
        print(i)
end 

-- upvalue test
function newCounter ()
        local i = 0
        return function ()   -- anonymous function
                        i = i + 1
                        return i
                end
end
c1 = newCounter()
print(c1())  --> 1
print(c1())  --> 2
print(c1())  --> 3


-- function call test
function func1(par1,par2)
        local local1 = par1 + par2
        return local1
end

function func2(par1,par2,par3)
        local local1 = par1 + par2
        local local2 = par3 * par3
        local1 = local1 + local2
        return local1
end

a=1
b=3
c=3.5

result1 = func1(a,b)
result2 = func2(a,b,c)
print("Result1 = ", result1)
print("Result2 = ", result2)

--math test
local a,b = 2,4; a = a + 4 * b - a / 2 ^ b % 3
print("a + 4 * b - a / 2 ^ b % 3 = ", a)

--conditional jumps test
if a ~= b 
        then print("a != b")
end
if a > b 
        then print("a > b")
end
if a >= b 
        then print("a >= b")
end
if a < b 
        then print("a < b")
end
if a <= b 
        then print("a <= b")
end
if a == b 
        then print("a == b")
end

Upcoming features:

GC - garbage collector. Currenly implemented GC heap standard functions, like:

    //initialize garbage collector and memory management
    void gcInit();
    //create new variable and return its number
    gcvarpt* gcNew(vartype type);
    //create new variable with given size and return its number
    gcvarpt* gcNew(vartype type, u08 size);
    //delete variable
    void gcDelete(gcvarpt* variable);

Tables - widly used in lua variable type. Will be implemented as hash table. GC should be implemented first.

Supported Operands

OP_CODE	NAME	Description
0	MOVE	Copy a value between registers
1	LOADK	Load a constant into a register
2	LOADBOOL	Load a boolean into a register
3	LOADNIL	Load nil values into a range of registers
4	GETUPVAL	Read an upvalue into a register
5	GETGLOBAL	Read a global variable into a register
7	SETGLOBAL	Write a register value into a global variable
8	SETUPVAL	Write a register value into an upvalue
12	ADD	Addition operator
13	SUB	Subtraction operator
14	MUL	Multiplication operator
15	DIV	Division operator
16	MOD	Modulus (remainder) operator
17	POW	Exponentiation operator
22	JMP	Unconditional jump
23	EQ	Equality test
24	LT	Less than test
25	LE	Less than or equal to test
28	CALL	Call a closure
36	CLOSURE	Create a closure of a function prototype
30	RETURN	Return from function call
31	FORLOOP	Iterate a numeric for loop
32	FORPREP	Initialization for a numeric for loop

Not yet supported

OP_CODE	NAME	Description
6	GETTABLE	Read a table element into a register
9	SETTABLE	Write a register value into a table element
10	NEWTABLE	Create a new table
11	SELF	Prepare an object method for calling
18	UNM	Unary minus operator
19	NOT	Logical NOT operator
20	LEN	Length operator
21	CONCAT	Concatenate a range of registers
26	TEST	Boolean test, with conditional jump
27	TESTSET	Boolean test, with conditional jump and assignment
29	TAILCALL	Perform a tail call
33	TFORLOOP	Iterate a generic for loop
34	SETLIST	Set a range of array elements for a table
35	CLOSE	Close a range of locals being used as upvalues
37	VARARG	Assign vararg function arguments to registers

Known Issues

GC could leak, implemented simple reference counting logic. Reference cycling is not supported.