From d805a4e0bf5ed6250d5dec6a48e951af364a860b Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@fri.uni-lj.si>
Date: Mon, 14 Dec 2015 20:26:23 +0100
Subject: Improve robot control script

---
 robot/main.py | 58 ++++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 42 insertions(+), 16 deletions(-)

diff --git a/robot/main.py b/robot/main.py
index b25f748..0b718b7 100755
--- a/robot/main.py
+++ b/robot/main.py
@@ -21,15 +21,17 @@
 
 PORT = 8000
 
+from fcntl import fcntl, F_GETFL, F_SETFL
+import io
 import json
-import multiprocessing
 import os
 import os.path
 import signal
+import subprocess
+import time
 
 import engineio
 import eventlet
-
 import ev3dev
 
 ev3_names = {
@@ -47,18 +49,32 @@ ev3_motors = [
 ]
 
 connections = set()
-process = None
-
-def _run_exec(program):
-    import ev3dev
-    from mindstorms_widgets import mindstorms_widgets
-    exec(program)
+running = False
+
+# Make a Python interpreter ready for running user program.
+def start_interpreter():
+    global running
+    process = subprocess.Popen(['python3', '-u'], bufsize=1, universal_newlines=True,
+                               stdin=subprocess.PIPE,
+                               stdout=subprocess.PIPE,
+                               stderr=subprocess.STDOUT)
+    # Set the non-blocking flag for stdout.
+    flags = fcntl(process.stdout.fileno(), F_GETFL)
+    fcntl(process.stdout.fileno(), F_SETFL, flags | os.O_NONBLOCK)
+    process.stdin.write("import ev3dev\n")
+    process.stdin.write("from mindstorms_widgets import mindstorms_widgets\n")
+    running = False
+    return process
+
+process = start_interpreter()
 
 def run(program):
-    global process
-    stop()
-    process = multiprocessing.Process(target=_run_exec, args=[program])
-    process.start()
+    global process, running
+    if running:
+        stop()
+    running = True
+    process.stdin.write("exec('''" + program + "''')\n")
+    process.stdin.close()
 
 def stop():
     global process
@@ -67,16 +83,16 @@ def stop():
             os.kill(process.pid, signal.SIGKILL)
         except:
             pass
-        process = None
-
     for motor in ev3_motors:
         if motor.connected:
             motor.stop(stop_command='brake')
+    process = start_interpreter()
 
 def notifier():
+    global process
+
     sensors_path = '/sys/class/lego-sensor'
     sensors = {}
-
     for sensor in os.listdir(sensors_path):
         path = os.path.join(sensors_path, sensor)
         with open(os.path.join(path, 'driver_name'), 'r') as f:
@@ -90,8 +106,17 @@ def notifier():
         sensors[path] = (friendly_name, multiplier, unit)
 
     while True:
-        eventlet.sleep(0.2)
         try:
+            if running:
+                text = process.stdout.readline()
+                if text:
+                    message = {'event': 'output', 'text': text}
+                    for sid in connections:
+                        eio.send(sid, json.dumps(message))
+                    continue
+                if process.poll() is not None:
+                    process = start_interpreter()
+
             message = {'event': 'update', 'sensors': {}}
             for path, (name, multiplier, unit) in sorted(sensors.items()):
                 with open(os.path.join(path, 'value0'), 'rb') as f:
@@ -105,6 +130,7 @@ def notifier():
                 eio.send(sid, text)
         except:
             pass
+        eventlet.sleep(0.2)
 
 eio = engineio.Server(async_mode='eventlet', cookie=None)
 app = engineio.Middleware(eio)
-- 
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