// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"flag"
"io"
"io/ioutil"
"log"
"net/http"
"os"
"os/exec"
"runtime"
"strconv"
"text/template"
)
var (
httpListen = flag.String("http", "127.0.0.1:3999", "host:port to listen on")
htmlOutput = flag.Bool("html", false, "render program output as HTML")
)
var (
// a source of numbers, for naming temporary files
uniq = make(chan int)
// the architecture-identifying character of the tool chain, 5, 6, or 8
archChar string
)
func main() {
flag.Parse()
// set archChar
switch runtime.GOARCH {
case "arm":
archChar = "5"
case "amd64":
archChar = "6"
case "386":
archChar = "8"
default:
log.Fatalln("unrecognized GOARCH:", runtime.GOARCH)
}
// source of unique numbers
go func() {
for i := 0; ; i++ {
uniq <- i
}
}()
http.HandleFunc("/", FrontPage)
http.HandleFunc("/compile", Compile)
log.Fatal(http.ListenAndServe(*httpListen, nil))
}
// FrontPage is an HTTP handler that renders the goplay interface.
// If a filename is supplied in the path component of the URI,
// its contents will be put in the interface's text area.
// Otherwise, the default "hello, world" program is displayed.
func FrontPage(w http.ResponseWriter, req *http.Request) {
data, err := ioutil.ReadFile(req.URL.Path[1:])
if err != nil {
data = helloWorld
}
frontPage.Execute(w, data)
}
// Compile is an HTTP handler that reads Go source code from the request,
// compiles and links the code (returning any errors), runs the program,
// and sends the program's output as the HTTP response.
func Compile(w http.ResponseWriter, req *http.Request) {
// x is the base name for .go, .6, executable files
x := os.TempDir() + "/compile" + strconv.Itoa(<-uniq)
src := x + ".go"
obj := x + "." + archChar
bin := x
if runtime.GOOS == "windows" {
bin += ".exe"
}
// write request Body to x.go
f, err := os.Create(src)
if err != nil {
error_(w, nil, err)
return
}
defer os.Remove(src)
defer f.Close()
_, err = io.Copy(f, req.Body)
if err != nil {
error_(w, nil, err)
return
}
f.Close()
// build x.go, creating x.6
out, err := run(archChar+"g", "-o", obj, src)
defer os.Remove(obj)
if err != nil {
error_(w, out, err)
return
}
// link x.6, creating x (the program binary)
out, err = run(archChar+"l", "-o", bin, obj)
defer os.Remove(bin)
if err != nil {
error_(w, out, err)
return
}
// run x
out, err = run(bin)
if err != nil {
error_(w, out, err)
}
// write the output of x as the http response
if *htmlOutput {
w.Write(out)
} else {
output.Execute(w, out)
}
}
// error writes compile, link, or runtime errors to the HTTP connection.
// The JavaScript interface uses the 404 status code to identify the error.
func error_(w http.ResponseWriter, out []byte, err error) {
w.WriteHeader(404)
if out != nil {
output.Execute(w, out)
} else {
output.Execute(w, err.Error())
}
}
// run executes the specified command and returns its output and an error.
func run(cmd ...string) ([]byte, error) {
return exec.Command(cmd[0], cmd[1:]...).CombinedOutput()
}
var frontPage = template.Must(template.New("frontPage").Parse(frontPageText)) // HTML template
var output = template.Must(template.New("output").Parse(outputText)) // HTML template
var outputText = `
{{printf "%s" . |html}}
`
var frontPageText = `
(Shift-Enter to compile and run.)
Compile and run after each keystroke
`
var helloWorld = []byte(`package main
import "fmt"
func main() {
fmt.Println("hello, world")
}
`)