Contents

• Design principle
• How about performance?
• Installation
• Usage
• Differences between Lua and GopherLua
• Standalone interpreter
• How to Contribute
• Libraries for GopherLua
• License
• Author

go get github.com/yuin/gopher-lua

import (
    "github.com/yuin/gopher-lua"
)

L := lua.NewState()
defer L.Close()
if err := L.DoString(`print("hello")`); err != nil {
    panic(err)
}

L := lua.NewState()
defer L.Close()
if err := L.DoFile("hello.lua"); err != nil {
    panic(err)
}

lv := L.Get(-1) // get the value at the top of the stack
if str, ok := lv.(lua.LString); ok {
    // lv is LString
    fmt.Println(string(str))
}
if lv.Type() != lua.LTString {
    panic("string required.")
}

lv := L.Get(-1) // get the value at the top of the stack
if tbl, ok := lv.(*lua.LTable); ok {
    // lv is LTable
    fmt.Println(L.ObjLen(tbl))
}

lv := L.Get(-1) // get the value at the top of the stack

if lv == LTrue { // correct
}

if bl, ok == lv.(lua.LBool); ok && bool(bl) { // wrong
}

lv := L.Get(-1) // get the value at the top of the stack
if LVIsFalse(lv) { // lv is nil or false
}

if LVAsBool(lv) { // lv is neither nil nor false
}

lua.RegistrySize = 1024 * 20
lua.CallStackSize = 1024
L := lua.NewState()
defer L.Close()

L := lua.NewState(lua.Options{
    CallStackSize: 120,
    RegistrySize:  120*20,
})

func Double(L *lua.LState) int {
    lv := L.ToInt(1)             /* get argument */
    L.Push(lua.LNumber(lv * 2)) /* push result */
    return 1                     /* number of results */
}

func main() {
    L := lua.NewState()
    defer L.Close()
    L.SetGlobal("double", L.NewFunction(Double)) /* Original lua_setglobal uses stack... */
}

print(double(20)) -- > "40"

type LGFunction func(*LState) int

co := L.NewThread() /* create a new thread */
fn := L.GetGlobal("coro").(*lua.LFunction) /* get function from lua */
for {
    st, err, values := L.Resume(co, fn)
    if st == lua.ResumeError {
        fmt.Println("yield break(error)")
        fmt.Println(err.Error())
        break
    }

    for i, lv := range values {
        fmt.Printf("%v : %v\n", i, lv)
    }

    if st == lua.ResumeOK {
        fmt.Println("yield break(ok)")
        break
    }
}

package mymodule

import (
    "github.com/yuin/gopher-lua"
)

func Loader(L *lua.LState) int {
    // register functions to the table
    mod := L.SetFuncs(L.NewTable(), exports)
    // register other stuff
    L.SetField(mod, "name", lua.LString("value"))

    // returns the module
    L.Push(mod)
    return 1
}

var exports = map[string]lua.LGFunction{
    "myfunc": myfunc,
}

func myfunc(L *lua.LState) int {
    return 0
}

package main

import (
    "./mymodule"
    "github.com/yuin/gopher-lua"
)

func main() {
    L := lua.NewState()
    defer L.Close()
    L.PreloadModule("mymodule", mymodule.Loader)
    if err := L.DoFile("main.lua"); err != nil {
        panic(err)
    }
}

local m = require("mymodule")
m.myfunc()
print(m.name)

L := lua.NewState()
defer L.Close()
if err := L.DoFile("double.lua"); err != nil {
    panic(err)
}
if err := L.CallByParam(lua.P{
    Fn: L.GetGlobal("double"),
    NRet: 1,
    Protect: true,
    }, lua.LNumber(10)); err != nil {
    panic(err)
}
ret := L.Get(-1) // returned value
L.Pop(1)  // remove received value

type Person struct {
    Name string
}

const luaPersonTypeName = "person"

// Registers my person type to given L.
func registerPersonType(L *lua.LState) {
    mt := L.NewTypeMetatable(luaPersonTypeName)
    L.SetGlobal("person", mt)
    // static attributes
    L.SetField(mt, "new", L.NewFunction(newPerson))
    // methods
    L.SetField(mt, "__index", L.SetFuncs(L.NewTable(), personMethods))
}

// Constructor
func newPerson(L *lua.LState) int {
    person := &Person{L.CheckString(1)}
    ud := L.NewUserData()
    ud.Value = person
    L.SetMetatable(ud, L.GetTypeMetatable(luaPersonTypeName))
    L.Push(ud)
    return 1
}

// Checks whether the first lua argument is a *LUserData with *Person and returns this *Person.
func checkPerson(L *lua.LState) *Person {
    ud := L.CheckUserData(1)
    if v, ok := ud.Value.(*Person); ok {
        return v
    }
    L.ArgError(1, "person expected")
    return nil
}

var personMethods = map[string]lua.LGFunction{
    "name": personGetSetName,
}

// Getter and setter for the Person#Name
func personGetSetName(L *lua.LState) int {
    p := checkPerson(L)
    if L.GetTop() == 2 {
        p.Name = L.CheckString(2)
        return 0
    }
    L.Push(lua.LString(p.Name))
    return 1
}

func main() {
    L := lua.NewState()
    defer L.Close()
    registerPersonType(L)
    if err := L.DoString(`
        p = person.new("Steeve")
        print(p:name()) -- "Steeve"
        p:name("Alice")
        print(p:name()) -- "Alice"
    `); err != nil {
        panic(err)
    }
}

func receiver(ch, quit chan lua.LValue) {
    L := lua.NewState()
    defer L.Close()
    L.SetGlobal("ch", lua.LChannel(ch))
    L.SetGlobal("quit", lua.LChannel(quit))
    if err := L.DoString(`
    local exit = false
    while not exit do
      channel.select(
        {"|<-", ch, function(ok, v)
          if not ok then
            print("channel closed")
            exit = true
          else
            print("received:", v)
          end
        end},
        {"|<-", quit, function(ok, v)
            print("quit")
            exit = true
        end}
      )
    end
  `); err != nil {
        panic(err)
    }
}

func sender(ch, quit chan lua.LValue) {
    L := lua.NewState()
    defer L.Close()
    L.SetGlobal("ch", lua.LChannel(ch))
    L.SetGlobal("quit", lua.LChannel(quit))
    if err := L.DoString(`
    ch:send("1")
    ch:send("2")
  `); err != nil {
        panic(err)
    }
    ch <- lua.LString("3")
    quit <- lua.LTrue
}

func main() {
    ch := make(chan lua.LValue)
    quit := make(chan lua.LValue)
    go receiver(ch, quit)
    go sender(ch, quit)
    time.Sleep(3 * time.Second)
}

local idx, recv, ok = channel.select(
  {"|<-", ch1},
  {"|<-", ch2}
)
if not ok then
    print("closed")
elseif idx == 1 then -- received from ch1
    print(recv)
elseif idx == 2 then -- received from ch2
    print(recv)
end

channel.select(
  {"|<-", ch1, function(ok, data)
    print(ok, data)
  end},
  {"<-|", ch2, "value", function(data)
    print(data)
  end},
  {"default", function()
    print("default action")
  end}
)

type lStatePool struct {
    m     sync.Mutex
    saved []*lua.LState
}

func (pl *lStatePool) Get() *lua.LState {
    pl.m.Lock()
    defer pl.m.Unlock()
    n := len(pl.saved)
    if n == 0 {
        return pl.New()
    }
    x := pl.saved[n-1]
    pl.saved = pl.saved[0 : n-1]
    return x
}

func (pl *lStatePool) New() *lua.LState {
    L := lua.NewState()
    // setting the L up here.
    // load scripts, set global variables, share channels, etc...
    return L
}

func (pl *lStatePool) Put(L *lua.LState) {
    pl.m.Lock()
    defer pl.m.Unlock()
    pl.saved = append(pl.saved, L)
}

func (pl *lStatePool) Shutdown() {
    for _, L := range pl.saved {
        L.Close()
    }
}

// Global LState pool
var luaPool = &lStatePool{
    saved: make([]*lua.LState, 0, 4),
}

func MyWorker() {
   L := luaPool.Get()
   defer luaPool.Put(L)
   /* your code here */
}

func main() {
    defer luaPool.Shutdown()
    go MyWorker()
    go MyWorker()
    /* etc... */
}

go get github.com/yuin/gopher-lua/cmd/glua

make build
make glua
make test