package jsre import ( "fmt" "io/ioutil" "sync" "time" "github.com/ethereum/go-ethereum/common" "github.com/robertkrimen/otto" ) /* JSRE is a generic JS runtime environment embedding the otto JS interpreter. It provides some helper functions to - load code from files - run code snippets - require libraries - bind native go objects */ type JSRE struct { assetPath string vm *otto.Otto evalQueue chan *evalReq stopEventLoop chan bool loopWg sync.WaitGroup } // jsTimer is a single timer instance with a callback function type jsTimer struct { timer *time.Timer duration time.Duration interval bool call otto.FunctionCall } // evalResult is a structure to store the result of any serialized vm execution type evalResult struct { result otto.Value err error } // evalReq is a serialized vm execution request put in evalQueue and processed by runEventLoop type evalReq struct { fn func(res *evalResult) done chan bool res evalResult } // runtime must be stopped with Stop() after use and cannot be used after stopping func New(assetPath string) *JSRE { re := &JSRE{ assetPath: assetPath, vm: otto.New(), } // load prettyprint func definition re.vm.Run(pp_js) re.vm.Set("loadScript", re.loadScript) re.evalQueue = make(chan *evalReq) re.stopEventLoop = make(chan bool) re.loopWg.Add(1) go re.runEventLoop() return re } // this function runs a piece of JS code either in a serialized way (when useEQ is true) or instantly, circumventing the evalQueue func (self *JSRE) run(src interface{}, useEQ bool) (value otto.Value, err error) { if useEQ { done := make(chan bool) req := &evalReq{ fn: func(res *evalResult) { res.result, res.err = self.vm.Run(src) }, done: done, } self.evalQueue <- req <-done return req.res.result, req.res.err } else { return self.vm.Run(src) } } /* This function runs the main event loop from a goroutine that is started when JSRE is created. Use Stop() before exiting to properly stop it. The event loop processes vm access requests from the evalQueue in a serialized way and calls timer callback functions at the appropriate time. Exported functions always access the vm through the event queue. You can call the functions of the otto vm directly to circumvent the queue. These functions should be used if and only if running a routine that was already called from JS through an RPC call. */ func (self *JSRE) runEventLoop() { registry := map[*jsTimer]*jsTimer{} ready := make(chan *jsTimer) newTimer := func(call otto.FunctionCall, interval bool) (*jsTimer, otto.Value) { delay, _ := call.Argument(1).ToInteger() if 0 >= delay { delay = 1 } timer := &jsTimer{ duration: time.Duration(delay) * time.Millisecond, call: call, interval: interval, } registry[timer] = timer timer.timer = time.AfterFunc(timer.duration, func() { ready <- timer }) value, err := call.Otto.ToValue(timer) if err != nil { panic(err) } return timer, value } setTimeout := func(call otto.FunctionCall) otto.Value { _, value := newTimer(call, false) return value } setInterval := func(call otto.FunctionCall) otto.Value { _, value := newTimer(call, true) return value } clearTimeout := func(call otto.FunctionCall) otto.Value { timer, _ := call.Argument(0).Export() if timer, ok := timer.(*jsTimer); ok { timer.timer.Stop() delete(registry, timer) } return otto.UndefinedValue() } self.vm.Set("setTimeout", setTimeout) self.vm.Set("setInterval", setInterval) self.vm.Set("clearTimeout", clearTimeout) self.vm.Set("clearInterval", clearTimeout) var waitForCallbacks bool loop: for { select { case timer := <-ready: // execute callback, remove/reschedule the timer var arguments []interface{} if len(timer.call.ArgumentList) > 2 { tmp := timer.call.ArgumentList[2:] arguments = make([]interface{}, 2+len(tmp)) for i, value := range tmp { arguments[i+2] = value } } else { arguments = make([]interface{}, 1) } arguments[0] = timer.call.ArgumentList[0] _, err := self.vm.Call(`Function.call.call`, nil, arguments...) if err != nil { fmt.Println("js error:", err, arguments) } if timer.interval { timer.timer.Reset(timer.duration) } else { delete(registry, timer) if waitForCallbacks && (len(registry) == 0) { break loop } } case evalReq := <-self.evalQueue: // run the code, send the result back evalReq.fn(&evalReq.res) close(evalReq.done) if waitForCallbacks && (len(registry) == 0) { break loop } case waitForCallbacks = <-self.stopEventLoop: if !waitForCallbacks || (len(registry) == 0) { break loop } } } for _, timer := range registry { timer.timer.Stop() delete(registry, timer) } self.loopWg.Done() } // stops the event loop before exit, optionally waits for all timers to expire func (self *JSRE) Stop(waitForCallbacks bool) { self.stopEventLoop <- waitForCallbacks self.loopWg.Wait() } // Exec(file) loads and runs the contents of a file // if a relative path is given, the jsre's assetPath is used func (self *JSRE) Exec(file string) error { return self.exec(common.AbsolutePath(self.assetPath, file), true) } // circumvents the eval queue, see runEventLoop func (self *JSRE) execWithoutEQ(file string) error { return self.exec(common.AbsolutePath(self.assetPath, file), false) } func (self *JSRE) exec(path string, useEQ bool) error { code, err := ioutil.ReadFile(path) if err != nil { return err } _, err = self.run(code, useEQ) return err } // assigns value v to a variable in the JS environment func (self *JSRE) Bind(name string, v interface{}) (err error) { self.Set(name, v) return } // runs a piece of JS code func (self *JSRE) Run(code string) (otto.Value, error) { return self.run(code, true) } // returns the value of a variable in the JS environment func (self *JSRE) Get(ns string) (otto.Value, error) { done := make(chan bool) req := &evalReq{ fn: func(res *evalResult) { res.result, res.err = self.vm.Get(ns) }, done: done, } self.evalQueue <- req <-done return req.res.result, req.res.err } // assigns value v to a variable in the JS environment func (self *JSRE) Set(ns string, v interface{}) error { done := make(chan bool) req := &evalReq{ fn: func(res *evalResult) { res.err = self.vm.Set(ns, v) }, done: done, } self.evalQueue <- req <-done return req.res.err } /* Executes a JS script from inside the currently executing JS code. Should only be called from inside an RPC routine. */ func (self *JSRE) loadScript(call otto.FunctionCall) otto.Value { file, err := call.Argument(0).ToString() if err != nil { return otto.FalseValue() } if err := self.execWithoutEQ(file); err != nil { // loadScript is only called from inside js fmt.Println("err:", err) return otto.FalseValue() } return otto.TrueValue() } // uses the "prettyPrint" JS function to format a value func (self *JSRE) PrettyPrint(v interface{}) (val otto.Value, err error) { var method otto.Value v, err = self.vm.ToValue(v) if err != nil { return } method, err = self.vm.Get("prettyPrint") if err != nil { return } return method.Call(method, v) } // creates an otto value from a go type func (self *JSRE) ToVal(v interface{}) otto.Value { result, err := self.vm.ToValue(v) if err != nil { fmt.Println("Value unknown:", err) return otto.UndefinedValue() } return result } // evaluates JS function and returns result in a pretty printed string format func (self *JSRE) Eval(code string) (s string, err error) { var val otto.Value val, err = self.Run(code) if err != nil { return } val, err = self.PrettyPrint(val) if err != nil { return } return fmt.Sprintf("%v", val), nil } // compiles and then runs a piece of JS code func (self *JSRE) Compile(fn string, src interface{}) error { script, err := self.vm.Compile(fn, src) if err != nil { return err } self.run(script, true) return nil }