fix(websocket): use the read part of the buffer instead of everything EE-5235 (#8685)

api/http/handler/websocket/stream.go

@@ -31,14 +31,14 @@ func streamFromReaderToWebsocket(websocketConn *websocket.Conn, reader io.Reader
 	out := make([]byte, readerBufferSize)
 
 	for {
-		_, err := reader.Read(out)
+		n, err := reader.Read(out)
 		if err != nil {
 			errorChan <- err
 
 			break
 		}
 
-		processedOutput := validString(string(out))
+		processedOutput := validString(string(out[:n]))
 		err = websocketConn.WriteMessage(websocket.TextMessage, []byte(processedOutput))
 		if err != nil {
 			errorChan <- err
@@ -49,7 +49,10 @@ func streamFromReaderToWebsocket(websocketConn *websocket.Conn, reader io.Reader
 }
 
 func validString(s string) string {
-	if !utf8.ValidString(s) {
+	if utf8.ValidString(s) {
+		return s
+	}
+
 	v := make([]rune, 0, len(s))
 
 	for i, r := range s {
@@ -63,8 +66,5 @@ func validString(s string) string {
 		v = append(v, r)
 	}
 
-		s = string(v)
-	}
-
-	return s
+	return string(v)
 }