// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package jsre provides execution environment for JavaScript.
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
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
}
// evalReq is a serialized vm execution request processed by runEventLoop.
type evalReq struct {
fn func(vm *otto.Otto)
done chan bool
}
// runtime must be stopped with Stop() after use and cannot be used after stopping
func New(assetPath string) *JSRE {
re := &JSRE{
assetPath: assetPath,
evalQueue: make(chan *evalReq),
stopEventLoop: make(chan bool),
}
re.loopWg.Add(1)
go re.runEventLoop()
re.Set("loadScript", re.loadScript)
re.Set("inspect", prettyPrintJS)
return re
}
// 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() {
vm := otto.New()
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()
}
vm.Set("_setTimeout", setTimeout)
vm.Set("_setInterval", setInterval)
vm.Run(`var setTimeout = function(args) {
if (arguments.length < 1) {
throw TypeError("Failed to execute 'setTimeout': 1 argument required, but only 0 present.");
}
return _setTimeout.apply(this, arguments);
}`)
vm.Run(`var setInterval = function(args) {
if (arguments.length < 1) {
throw TypeError("Failed to execute 'setInterval': 1 argument required, but only 0 present.");
}
return _setInterval.apply(this, arguments);
}`)
vm.Set("clearTimeout", clearTimeout)
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 := vm.Call(`Function.call.call`, nil, arguments...)
if err != nil {
fmt.Println("js error:", err, arguments)
}
_, inreg := registry[timer] // when clearInterval is called from within the callback don't reset it
if timer.interval && inreg {
timer.timer.Reset(timer.duration)
} else {
delete(registry, timer)
if waitForCallbacks && (len(registry) == 0) {
break loop
}
}
case req := <-self.evalQueue:
// run the code, send the result back
req.fn(vm)
close(req.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()
}
// do schedules the given function on the event loop.
func (self *JSRE) do(fn func(*otto.Otto)) {
done := make(chan bool)
req := &evalReq{fn, done}
self.evalQueue <- req
<-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 {
code, err := ioutil.ReadFile(common.AbsolutePath(self.assetPath, file))
if err != nil {
return err
}
self.do(func(vm *otto.Otto) { _, err = vm.Run(code) })
return err
}
// Bind assigns value v to a variable in the JS environment
// This method is deprecated, use Set.
func (self *JSRE) Bind(name string, v interface{}) error {
return self.Set(name, v)
}
// Run runs a piece of JS code.
func (self *JSRE) Run(code string) (v otto.Value, err error) {
self.do(func(vm *otto.Otto) { v, err = vm.Run(code) })
return v, err
}
// Get returns the value of a variable in the JS environment.
func (self *JSRE) Get(ns string) (v otto.Value, err error) {
self.do(func(vm *otto.Otto) { v, err = vm.Get(ns) })
return v, err
}
// Set assigns value v to a variable in the JS environment.
func (self *JSRE) Set(ns string, v interface{}) (err error) {
self.do(func(vm *otto.Otto) { err = vm.Set(ns, v) })
return err
}
// loadScript executes a JS script from inside the currently executing JS code.
func (self *JSRE) loadScript(call otto.FunctionCall) otto.Value {
file, err := call.Argument(0).ToString()
if err != nil {
// TODO: throw exception
return otto.FalseValue()
}
file = common.AbsolutePath(self.assetPath, file)
source, err := ioutil.ReadFile(file)
if err != nil {
// TODO: throw exception
return otto.FalseValue()
}
if _, err := compileAndRun(call.Otto, file, source); err != nil {
// TODO: throw exception
fmt.Println("err:", err)
return otto.FalseValue()
}
// TODO: return evaluation result
return otto.TrueValue()
}
// EvalAndPrettyPrint evaluates code and pretty prints the result to
// standard output.
func (self *JSRE) EvalAndPrettyPrint(code string) (err error) {
self.do(func(vm *otto.Otto) {
var val otto.Value
val, err = vm.Run(code)
if err != nil {
return
}
prettyPrint(vm, val)
fmt.Println()
})
return err
}
// Compile compiles and then runs a piece of JS code.
func (self *JSRE) Compile(filename string, src interface{}) (err error) {
self.do(func(vm *otto.Otto) { _, err = compileAndRun(vm, filename, src) })
return err
}
func compileAndRun(vm *otto.Otto, filename string, src interface{}) (otto.Value, error) {
script, err := vm.Compile(filename, src)
if err != nil {
return otto.Value{}, err
}
return vm.Run(script)
}
