portainer/api/http/handler/websocket/stream.go

package websocket

import (
	"io"
	"unicode/utf8"

	"github.com/gorilla/websocket"
)

const readerBufferSize = 2048

func streamFromWebsocketToWriter(websocketConn *websocket.Conn, writer io.Writer, errorChan chan error) {
	for {
		_, in, err := websocketConn.ReadMessage()
		if err != nil {
			errorChan <- err

			break
		}

		_, err = writer.Write(in)
		if err != nil {
			errorChan <- err

			break
		}
	}
}

func streamFromReaderToWebsocket(websocketConn *websocket.Conn, reader io.Reader, errorChan chan error) {
	out := make([]byte, readerBufferSize)

	for {
		n, err := reader.Read(out)
		if err != nil {
			errorChan <- err

			break
		}

		processedOutput := validString(string(out[:n]))
		err = websocketConn.WriteMessage(websocket.TextMessage, []byte(processedOutput))
		if err != nil {
			errorChan <- err

			break
		}
	}
}

func validString(s string) string {
	if utf8.ValidString(s) {
		return s
	}

	v := make([]rune, 0, len(s))

	for i, r := range s {
		if r == utf8.RuneError {
			_, size := utf8.DecodeRuneInString(s[i:])
			if size == 1 {
				continue
			}
		}

		v = append(v, r)
	}

	return string(v)
}