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package engine
import (
"bytes"
"errors"
"fmt"
"image"
"image/png"
"io"
"net/http"
"os/exec"
"sync/atomic"
"github.com/mumax/3/httpfs"
)
var nPlots int32 // counts number of active gnuplot processes
const MAX_GNUPLOTS = 5 // maximum allowed number of gnuplot processes
func (g *guistate) servePlot(w http.ResponseWriter, r *http.Request) {
out := []byte{}
// handle error and return wheter err != nil.
handle := func(err error) bool {
if err != nil {
w.Write(emptyIMG())
g.Set("plotErr", err.Error()+string(out))
return true
} else {
return false
}
}
// limit max processes
atomic.AddInt32(&nPlots, 1)
defer atomic.AddInt32(&nPlots, -1)
if atomic.LoadInt32(&nPlots) > MAX_GNUPLOTS {
handle(errors.New("too many gnuplot processes"))
return
}
a := g.StringValue("usingx")
b := g.StringValue("usingy")
cmd := "gnuplot"
args := []string{"-e", fmt.Sprintf(`set format x "%%g"; set key off; set format y "%%g"; set term svg size 480,320 font 'Arial,10'; plot "-" u %v:%v w li; set output;exit;`, a, b)}
excmd := exec.Command(cmd, args...)
stdin, err := excmd.StdinPipe()
if handle(err) {
return
}
stdout, err := excmd.StdoutPipe()
if handle(err) {
return
}
data, err := httpfs.Read(fmt.Sprintf(`%vtable.txt`, OD()))
if handle(err) {
return
}
err = excmd.Start()
if handle(err) {
return
}
defer excmd.Wait()
_, err = stdin.Write(data)
if handle(err) {
return
}
err = stdin.Close()
if handle(err) {
return
}
out, err = io.ReadAll(stdout)
if handle(err) {
return
}
w.Header().Set("Content-Type", "image/svg+xml")
w.Write(out)
g.Set("plotErr", "")
}
var empty_img []byte
// empty image to show if there's no plot...
func emptyIMG() []byte {
if empty_img == nil {
o := bytes.NewBuffer(nil)
png.Encode(o, image.NewNRGBA(image.Rect(0, 0, 4, 4)))
empty_img = o.Bytes()
}
return empty_img
}
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