openwebrx-clone/openwebrx.py

#!/usr/bin/python2
print "" # python2.7 is required to run OpenWebRX instead of python3. Please run me by: python2 openwebrx.py
"""

	This file is part of OpenWebRX, 
	an open-source SDR receiver software with a web UI.
	Copyright (c) 2013-2015 by Andras Retzler <randras@sdr.hu>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
sw_version="v0.12+"

import os
import code
import importlib
import plugins
import plugins.dsp
import thread
import time
import datetime
import subprocess
import os 
from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
from SocketServer import ThreadingMixIn
import fcntl
import time
import md5
import random
import threading
import sys
import traceback
from collections import namedtuple
import Queue
import ctypes

#import rtl_mus
import rxws
import uuid
import signal
import socket

try: import sdrhu
except: sdrhu=False
avatar_ctime=""

#pypy compatibility
try: import dl
except: pass
try: import __pypy__
except: pass
pypy="__pypy__" in globals()

def import_all_plugins(directory):
	for subdir in os.listdir(directory):
		if os.path.isdir(directory+subdir) and not subdir[0]=="_":
			exact_path=directory+subdir+"/plugin.py"
			if os.path.isfile(exact_path):
				importname=(directory+subdir+"/plugin").replace("/",".")
				print "[openwebrx-import] Found plugin:",importname
				importlib.import_module(importname)

class MultiThreadHTTPServer(ThreadingMixIn, HTTPServer):
    pass 

def handle_signal(signal, frame):
	global spectrum_dsp
	print "[openwebrx] Ctrl+C: aborting."
	cleanup_clients(True)
	spectrum_dsp.stop()
	os._exit(1) #not too graceful exit

def access_log(data):
	global logs
	logs.access_log.write("["+datetime.datetime.now().isoformat()+"] "+data+"\n")
	logs.access_log.flush()

receiver_failed=spectrum_thread_watchdog_last_tick=rtl_thread=spectrum_dsp=server_fail=None

def main():
	global clients, clients_mutex, pypy, lock_try_time, avatar_ctime, cfg, logs
	global serverfail, rtl_thread
	print
	print "OpenWebRX - Open Source SDR Web App for Everyone!  | for license see LICENSE file in the package"
	print "_________________________________________________________________________________________________"
	print 
	print "Author contact info:    Andras Retzler, HA7ILM <randras@sdr.hu>"
	print 

	no_arguments=len(sys.argv)==1
	if no_arguments: print "[openwebrx-main] Configuration script not specified. I will use: \"config_webrx.py\""
	cfg=__import__("config_webrx" if no_arguments else sys.argv[1])
	for option in ("access_log","csdr_dynamic_bufsize","csdr_print_bufsizes","csdr_through"): 
		if not option in dir(cfg): setattr(cfg, option, False) #initialize optional config parameters

	#Open log files
	logs = type("logs_class", (object,), {"access_log":open(cfg.access_log if cfg.access_log else "/dev/null","a"), "error_log":""})()
	
	#Set signal handler
	signal.signal(signal.SIGINT, handle_signal) #http://stackoverflow.com/questions/1112343/how-do-i-capture-sigint-in-python

	#Load plugins
	import_all_plugins("plugins/dsp/")

	#Pypy
	if pypy: print "pypy detected (and now something completely different: a c code is expected to run at a speed of 3*10^8 m/s?)"

	#Change process name to "openwebrx" (to be seen in ps)
	try:
		for libcpath in ["/lib/i386-linux-gnu/libc.so.6","/lib/libc.so.6"]:
			if os.path.exists(libcpath):
				libc = dl.open(libcpath)
				libc.call("prctl", 15, "openwebrx", 0, 0, 0)
				break
	except:
		pass

	#Start rtl thread
	if os.system("ncat --version > /dev/null") == 32512: #check for ncat
		print "[openwebrx-main] Error: ncat not detected, please install it! The ncat tool is a netcat alternative, used for distributing the I/Q data stream. It is usually available in the nmap package (sudo apt-get install nmap). For more explanation, look into the README.md"
		return 
	if cfg.start_rtl_thread:
		cfg.start_rtl_command += "| ncat -4l %d -k --send-only --allow 127.0.0.1" % cfg.iq_server_port
		rtl_thread=threading.Thread(target = lambda:subprocess.Popen(cfg.start_rtl_command, shell=True),  args=())
		rtl_thread.start()
		print "[openwebrx-main] Started rtl_thread: "+cfg.start_rtl_command
	time.sleep(1) #wait until it really starts	

	#Initialize clients
	clients=[]
	clients_mutex=threading.Lock()
	lock_try_time=0

	#Start watchdog thread
	print "[openwebrx-main] Starting watchdog threads."
	mutex_test_thread=threading.Thread(target = mutex_test_thread_function, args = ())
	mutex_test_thread.start()
	mutex_watchdog_thread=threading.Thread(target = mutex_watchdog_thread_function, args = ())
	mutex_watchdog_thread.start()
	

	#Start spectrum thread
	print "[openwebrx-main] Starting spectrum thread."
	spectrum_thread=threading.Thread(target = spectrum_thread_function, args = ())
	spectrum_thread.start()
	spectrum_watchdog_thread=threading.Thread(target = spectrum_watchdog_thread_function, args = ())
	spectrum_watchdog_thread.start()

	get_cpu_usage()
	bcastmsg_thread=threading.Thread(target = bcastmsg_thread_function, args = ())
	bcastmsg_thread.start()
	
	#threading.Thread(target = measure_thread_function, args = ()).start()

	#Start sdr.hu update thread
	if sdrhu and cfg.sdrhu_key and cfg.sdrhu_public_listing: 
		print "[openwebrx-main] Starting sdr.hu update thread..."
		avatar_ctime=str(os.path.getctime("htdocs/gfx/openwebrx-avatar.png"))
		sdrhu_thread=threading.Thread(target = sdrhu.run, args = ())
		sdrhu_thread.start()
	
	#Start HTTP thread
	httpd = MultiThreadHTTPServer(('', cfg.web_port), WebRXHandler)
	print('[openwebrx-main] Starting HTTP server.')
	access_log("Starting OpenWebRX...")
	httpd.serve_forever()


# This is a debug function below:
measure_value=0
def measure_thread_function():
	global measure_value
	while True:	
		print "[openwebrx-measure] value is",measure_value
		measure_value=0
		time.sleep(1)

def bcastmsg_thread_function():
	global clients
	while True:
		time.sleep(3)
		try: cpu_usage=get_cpu_usage()
		except: cpu_usage=0
		cma("bcastmsg_thread")
		for i in range(0,len(clients)):
			clients[i].bcastmsg="MSG cpu_usage={0} clients={1}".format(int(cpu_usage*100),len(clients))
		cmr()

def mutex_test_thread_function():
	global clients_mutex, lock_try_time
	while True:
		time.sleep(0.5)
		lock_try_time=time.time()
		clients_mutex.acquire()
		clients_mutex.release()
		lock_try_time=0

def cma(what): #clients_mutex acquire
	global clients_mutex
	global clients_mutex_locker
	if not clients_mutex.locked(): clients_mutex_locker = what
	clients_mutex.acquire()

def cmr():
	global clients_mutex
	global clients_mutex_locker
	clients_mutex_locker = None
	clients_mutex.release()

def mutex_watchdog_thread_function():
	global lock_try_time
	global clients_mutex_locker
	global clients_mutex
	while True:
		if lock_try_time != 0 and time.time()-lock_try_time > 3.0: 
			#if 3 seconds pass without unlock
			print "[openwebrx-mutex-watchdog] Mutex unlock timeout. Locker: \""+str(clients_mutex_locker)+"\" Now unlocking..." 
			clients_mutex.release()
		time.sleep(0.5)	

def spectrum_watchdog_thread_function():
	global spectrum_thread_watchdog_last_tick, receiver_failed
	while True:
		time.sleep(60)
		if spectrum_thread_watchdog_last_tick and time.time()-spectrum_thread_watchdog_last_tick > 60.0: 
			print "[openwebrx-spectrum-watchdog] Spectrum timeout. Seems like no I/Q data is coming from the receiver.\nIf you're using RTL-SDR, the receiver hardware may randomly fail under some circumstances:\n1) high temperature,\n2) insufficient current available from the USB port."
			print "[openwebrx-spectrum-watchdog] Deactivating receiver."
			receiver_failed="spectrum"
			return

def check_server():
	global spectrum_dsp, server_fail, rtl_thread
	if server_fail: return server_fail	
	#print spectrum_dsp.process.poll()
	if spectrum_dsp and spectrum_dsp.process.poll()!=None: server_fail = "spectrum_thread dsp subprocess failed"
	#if rtl_thread and not rtl_thread.is_alive(): server_fail = "rtl_thread failed"
	if server_fail: print "[openwebrx-check_server] >>>>>>> ERROR:", server_fail
	return server_fail

def apply_csdr_cfg_to_dsp(dsp):
	dsp.csdr_dynamic_bufsize = cfg.csdr_dynamic_bufsize
	dsp.csdr_print_bufsizes = cfg.csdr_print_bufsizes
	dsp.csdr_through = cfg.csdr_through	

def spectrum_thread_function():
	global clients, spectrum_dsp, spectrum_thread_watchdog_last_tick
	spectrum_dsp=dsp=getattr(plugins.dsp,cfg.dsp_plugin).plugin.dsp_plugin()
	dsp.nc_port=cfg.iq_server_port
	dsp.set_demodulator("fft")
	dsp.set_samp_rate(cfg.samp_rate)
	dsp.set_fft_size(cfg.fft_size)
	dsp.set_fft_fps(cfg.fft_fps)
	dsp.set_fft_compression(cfg.fft_compression)
	dsp.set_format_conversion(cfg.format_conversion)
	apply_csdr_cfg_to_dsp(dsp)
	sleep_sec=0.87/cfg.fft_fps
	print "[openwebrx-spectrum] Spectrum thread initialized successfully."
	dsp.start()
	if cfg.csdr_dynamic_bufsize: 
		dsp.read(8) #dummy read to skip bufsize & preamble
		print "[openwebrx-spectrum] Note: CSDR_DYNAMIC_BUFSIZE_ON = 1"
	print "[openwebrx-spectrum] Spectrum thread started." 
	bytes_to_read=int(dsp.get_fft_bytes_to_read())
	spectrum_thread_counter=0
	while True:
		data=dsp.read(bytes_to_read)
		#print "gotcha",len(data),"bytes of spectrum data via spectrum_thread_function()"
		if spectrum_thread_counter >= cfg.fft_fps: 
			spectrum_thread_counter=0
			spectrum_thread_watchdog_last_tick = time.time() #once every second
		else: spectrum_thread_counter+=1
		cma("spectrum_thread")
		correction=0
		for i in range(0,len(clients)):
			i-=correction
			if (clients[i].ws_started):
				if clients[i].spectrum_queue.full():
					print "[openwebrx-spectrum] client spectrum queue full, closing it."
					close_client(i, False)
					correction+=1
				else:
					clients[i].spectrum_queue.put([data]) # add new string by "reference" to all clients
		cmr()
	
def get_client_by_id(client_id, use_mutex=True):
	global clients
	output=-1
	if use_mutex: cma("get_client_by_id")
	for i in range(0,len(clients)):
		if(clients[i].id==client_id):
			output=i
			break
	if use_mutex: cmr()
	if output==-1:
		raise ClientNotFoundException
	else:
		return output

def log_client(client, what):
	print "[openwebrx-httpd] client {0}#{1} :: {2}".format(client.ip,client.id,what)

def cleanup_clients(end_all=False):
	# - if a client doesn't open websocket for too long time, we drop it
	# - or if end_all is true, we drop all clients
	global clients
	cma("cleanup_clients")
	correction=0
	for i in range(0,len(clients)):
		i-=correction
		#print "cleanup_clients:: len(clients)=", len(clients), "i=", i
		if end_all or ((not clients[i].ws_started) and (time.time()-clients[i].gen_time)>45):
			if not end_all: print "[openwebrx] cleanup_clients :: client timeout to open WebSocket"
			close_client(i, False)
			correction+=1
	cmr()

def generate_client_id(ip):
	#add a client
	global clients
	new_client=namedtuple("ClientStruct", "id gen_time ws_started sprectum_queue ip closed bcastmsg dsp")	
	new_client.id=md5.md5(str(random.random())).hexdigest()
	new_client.gen_time=time.time()
	new_client.ws_started=False # to check whether client has ever tried to open the websocket
	new_client.spectrum_queue=Queue.Queue(1000)
	new_client.ip=ip
	new_client.bcastmsg=""
	new_client.closed=[False] #byref, not exactly sure if required
	new_client.dsp=None
	cma("generate_client_id")
	clients.append(new_client)
	log_client(new_client,"client added. Clients now: {0}".format(len(clients)))
	cmr()
	cleanup_clients()
	return new_client.id

def close_client(i, use_mutex=True):
	global clients
	log_client(clients[i],"client being closed.")
	if use_mutex: cma("close_client")
	try:
		clients[i].dsp.stop()
	except:
		exc_type, exc_value, exc_traceback = sys.exc_info()
		print "[openwebrx] close_client dsp.stop() :: error -",exc_type,exc_value
		traceback.print_tb(exc_traceback)
	clients[i].closed[0]=True
	access_log("Stopped streaming to client: "+clients[i].ip+"#"+str(clients[i].id)+" (users now: "+str(len(clients)-1)+")")
	del clients[i]
	if use_mutex: cmr()

# http://www.codeproject.com/Articles/462525/Simple-HTTP-Server-and-Client-in-Python
# some ideas are used from the artice above

class WebRXHandler(BaseHTTPRequestHandler):    
	def proc_read_thread():
		pass

	def send_302(self,what):
		self.send_response(302)
		self.send_header('Content-type','text/html')
		self.send_header("Location", "http://{0}:{1}/{2}".format(cfg.server_hostname,cfg.web_port,what))
		self.end_headers()
		self.wfile.write("<html><body><h1>Object moved</h1>Please <a href=\"/{0}\">click here</a> to continue.</body></html>".format(what))


	def do_GET(self):
		self.connection.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
		global dsp_plugin, clients_mutex, clients, avatar_ctime, sw_version, receiver_failed
		rootdir = 'htdocs' 
		self.path=self.path.replace("..","")
		path_temp_parts=self.path.split("?")
		self.path=path_temp_parts[0]
		request_param=path_temp_parts[1] if(len(path_temp_parts)>1) else "" 
		access_log("GET "+self.path+" from "+self.client_address[0])
		try:
			if self.path=="/":
				self.path="/index.wrx"
			# there's even another cool tip at http://stackoverflow.com/questions/4419650/how-to-implement-timeout-in-basehttpserver-basehttprequesthandler-python
			#if self.path[:5]=="/lock": cma("do_GET /lock/") # to test mutex_watchdog_thread. Do not uncomment in production environment!
			if self.path[:4]=="/ws/":
				if receiver_failed: self.send_error(500,"Internal server error")
				try:
					# ========= WebSocket handshake  =========
					ws_success=True
					try:				
						rxws.handshake(self)
						cma("do_GET /ws/")				
						client_i=get_client_by_id(self.path[4:], False)
						myclient=clients[client_i]
					except rxws.WebSocketException: ws_success=False
					except ClientNotFoundException: ws_success=False
					finally:
						if clients_mutex.locked(): cmr()
					if not ws_success:
						self.send_error(400, 'Bad request.')
						return

					# ========= Client handshake =========
					if myclient.ws_started:
						print "[openwebrx-httpd] error: second WS connection with the same client id, throwing it."
						self.send_error(400, 'Bad request.') #client already started
						return
					rxws.send(self, "CLIENT DE SERVER openwebrx.py")
					client_ans=rxws.recv(self, True)
					if client_ans[:16]!="SERVER DE CLIENT":
						rxws.send("ERR Bad answer.")
						return
					myclient.ws_started=True
					#send default parameters
					rxws.send(self, "MSG center_freq={0} bandwidth={1} fft_size={2} fft_fps={3} audio_compression={4} fft_compression={5} max_clients={6} setup".format(str(cfg.shown_center_freq),str(cfg.samp_rate),cfg.fft_size,cfg.fft_fps,cfg.audio_compression,cfg.fft_compression,cfg.max_clients))

					# ========= Initialize DSP =========
					dsp=getattr(plugins.dsp,cfg.dsp_plugin).plugin.dsp_plugin()
					dsp_initialized=False
					dsp.set_audio_compression(cfg.audio_compression)
					dsp.set_format_conversion(cfg.format_conversion)
					dsp.set_offset_freq(0)
					dsp.set_bpf(-4000,4000)
					dsp.nc_port=cfg.iq_server_port
					apply_csdr_cfg_to_dsp(dsp)
					myclient.dsp=dsp
					
					access_log("Started streaming to client: "+self.client_address[0]+"#"+myclient.id+" (users now: "+str(len(clients))+")")

					while True:
						if myclient.closed[0]: 
							print "[openwebrx-httpd:ws] client closed by other thread"
							break

						# ========= send audio =========
						if dsp_initialized:
							temp_audio_data=dsp.read(256)
							rxws.send(self, temp_audio_data, "AUD ")

						# ========= send spectrum =========
						while not myclient.spectrum_queue.empty():
							spectrum_data=myclient.spectrum_queue.get()
							#spectrum_data_mid=len(spectrum_data[0])/2
							#rxws.send(self, spectrum_data[0][spectrum_data_mid:]+spectrum_data[0][:spectrum_data_mid], "FFT ") 
							# (it seems GNU Radio exchanges the first and second part of the FFT output, we correct it)
							rxws.send(self, spectrum_data[0],"FFT ")

						# ========= send bcastmsg =========
						if myclient.bcastmsg!="":
							rxws.send(self,myclient.bcastmsg)
							myclient.bcastmsg=""

						# ========= process commands =========
						while True:
							rdata=rxws.recv(self, False)
							if not rdata: break
							#try:
							elif rdata[:3]=="SET":
								print "[openwebrx-httpd:ws,%d] command: %s"%(client_i,rdata)
								pairs=rdata[4:].split(" ")
								bpf_set=False
								new_bpf=dsp.get_bpf()
								filter_limit=dsp.get_output_rate()/2
								for pair in pairs:
									param_name, param_value = pair.split("=")
									if param_name == "low_cut" and -filter_limit <= float(param_value) <= filter_limit:
										bpf_set=True
										new_bpf[0]=int(param_value)
									elif param_name == "high_cut" and -filter_limit <= float(param_value) <= filter_limit:
										bpf_set=True
										new_bpf[1]=int(param_value)
									elif param_name == "offset_freq" and -cfg.samp_rate/2 <= float(param_value) <= cfg.samp_rate/2:
										dsp.set_offset_freq(int(param_value))
									elif param_name=="mod":
										if (dsp.get_demodulator()!=param_value):
											if dsp_initialized: dsp.stop()
											dsp.set_demodulator(param_value)
											if dsp_initialized: dsp.start()
									elif param_name == "output_rate":
										if not dsp_initialized: 
											dsp.set_output_rate(int(param_value))
											dsp.set_samp_rate(cfg.samp_rate)
									elif param_name=="action" and param_value=="start":
										if not dsp_initialized: 
											dsp.start()
											dsp_initialized=True
									else:
										print "[openwebrx-httpd:ws] invalid parameter"
								if bpf_set:
									dsp.set_bpf(*new_bpf)
								#code.interact(local=locals())
				except:
					exc_type, exc_value, exc_traceback = sys.exc_info()
					if exc_value[0]==32: #"broken pipe", client disconnected
						pass
					elif exc_value[0]==11: #"resource unavailable" on recv, client disconnected	
						pass
					else:	
						print "[openwebrx-httpd] error in /ws/ handler: ",exc_type,exc_value
						traceback.print_tb(exc_traceback)

				#stop dsp for the disconnected client				
				try:
					dsp.stop()
					del dsp
				except:
					print "[openwebrx-httpd] error in dsp.stop()"

				#delete disconnected client
				try:
					cma("do_GET /ws/ delete disconnected")
					id_to_close=get_client_by_id(myclient.id,False)
					close_client(id_to_close,False)
				except:
					exc_type, exc_value, exc_traceback = sys.exc_info()
					print "[openwebrx-httpd] client cannot be closed: ",exc_type,exc_value
					traceback.print_tb(exc_traceback)
				finally:
					cmr()
				return
			elif self.path in ("/status", "/status/"):
				#self.send_header('Content-type','text/plain')
				getbands=lambda: str(int(cfg.shown_center_freq-cfg.samp_rate/2))+"-"+str(int(cfg.shown_center_freq+cfg.samp_rate/2))
				self.wfile.write("status="+("inactive" if receiver_failed else "active")+"\nname="+cfg.receiver_name+"\nsdr_hw="+cfg.receiver_device+"\nop_email="+cfg.receiver_admin+"\nbands="+getbands()+"\nusers="+str(len(clients))+"\nusers_max="+str(cfg.max_clients)+"\navatar_ctime="+avatar_ctime+"\ngps="+str(cfg.receiver_gps)+"\nasl="+str(cfg.receiver_asl)+"\nloc="+cfg.receiver_location+"\nsw_version="+sw_version+"\nantenna="+cfg.receiver_ant+"\n")
				print "[openwebrx-httpd] GET /status/ from",self.client_address[0]			
			else:
				f=open(rootdir+self.path)
				data=f.read()
				extension=self.path[(len(self.path)-4):len(self.path)]
				extension=extension[2:] if extension[1]=='.' else extension[1:]
				checkresult=check_server()
				if extension == "wrx" and (checkresult or receiver_failed):
					self.send_302("inactive.html")
					return
				if extension == "wrx" and ((self.headers['user-agent'].count("Chrome")==0 and self.headers['user-agent'].count("Firefox")==0 and (not "Googlebot" in self.headers['user-agent'])) if 'user-agent' in self.headers.keys() else True) and (not request_param.count("unsupported")):
					self.send_302("upgrade.html")
					return
				if extension == "wrx" and cfg.max_clients<=len(clients):
					self.send_302("retry.html")
					return
				self.send_response(200)
				if(("wrx","html","htm").count(extension)):
					self.send_header('Content-type','text/html')
				elif(extension=="js"):
					self.send_header('Content-type','text/javascript')
				elif(extension=="css"):
					self.send_header('Content-type','text/css')
				self.end_headers()		
				if extension == "wrx":
					replace_dictionary=(
						("%[RX_PHOTO_DESC]",cfg.photo_desc),
						("%[CLIENT_ID]", generate_client_id(self.client_address[0])) if "%[CLIENT_ID]" in data else "",
						("%[WS_URL]","ws://"+cfg.server_hostname+":"+str(cfg.web_port)+"/ws/"),
						("%[RX_TITLE]",cfg.receiver_name),
						("%[RX_LOC]",cfg.receiver_location),
						("%[RX_QRA]",cfg.receiver_qra),
						("%[RX_ASL]",str(cfg.receiver_asl)),
						("%[RX_GPS]",str(cfg.receiver_gps[0])+","+str(cfg.receiver_gps[1])),
						("%[RX_PHOTO_HEIGHT]",str(cfg.photo_height)),("%[RX_PHOTO_TITLE]",cfg.photo_title),
						("%[RX_ADMIN]",cfg.receiver_admin),
						("%[RX_ANT]",cfg.receiver_ant),
						("%[RX_DEVICE]",cfg.receiver_device),
						("%[AUDIO_BUFSIZE]",str(cfg.client_audio_buffer_size)),
						("%[START_OFFSET_FREQ]",str(cfg.start_freq-cfg.center_freq)),
						("%[START_MOD]",cfg.start_mod)
					)
					for rule in replace_dictionary:
						while data.find(rule[0])!=-1:
							data=data.replace(rule[0],rule[1])
				self.wfile.write(data)
				f.close()
			return
		except IOError:
			self.send_error(404, 'Invalid path.')
		except:
			exc_type, exc_value, exc_traceback = sys.exc_info()
			print "[openwebrx-httpd] error (@outside):", exc_type, exc_value
			traceback.print_tb(exc_traceback)
			

class ClientNotFoundException(Exception):
	pass

last_worktime=0
last_idletime=0

def get_cpu_usage():
	global last_worktime, last_idletime
	f=open("/proc/stat","r")
	line=""
	while not "cpu " in line: line=f.readline()
	f.close()
	spl=line.split(" ")
	worktime=int(spl[2])+int(spl[3])+int(spl[4])
	idletime=int(spl[5])
	dworktime=(worktime-last_worktime)
	didletime=(idletime-last_idletime)
	rate=float(dworktime)/(didletime+dworktime)
	last_worktime=worktime
	last_idletime=idletime
	if(last_worktime==0): return 0
	return rate


if __name__=="__main__":
	main()