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annotate server/utils.py @ 385:a827f1c5ddbe

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don't stay awake for any command - chews battery if server goes down
author Matt Johnston <matt@ucc.asn.au>
date Mon, 09 Jul 2012 00:39:07 +0800
parents dae8eb26eaa3
children 51d889ad39a3
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1 import os
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2 import sys
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3 #import ctypes
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4 import time
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5 import select
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6
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7 lightblue = None
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8 try:
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9 import lightblue
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10 except ImportError:
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11 pass
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12
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13 DEFAULT_TRIES = 3
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14 READLINE_SELECT_TIMEOUT = 4
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15
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16 __all__ = ('monotonic_time', 'retry')
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17
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18 clock_gettime = None
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19 no_clock_gettime = True
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20 def monotonic_time():
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21 global clock_gettime
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22 global no_clock_gettime
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23 if no_clock_gettime:
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24 return time.time()
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25
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26 class timespec(ctypes.Structure):
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27 _fields_ = [
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28 ('tv_sec', ctypes.c_long),
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29 ('tv_nsec', ctypes.c_long)
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30 ]
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31 if not clock_gettime:
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32 try:
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33 librt = ctypes.CDLL('librt.so.0', use_errno=True)
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34 clock_gettime = librt.clock_gettime
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35 clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
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36 except:
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37 print>>sys.stderr, "No clock_gettime(), using fake fallback."
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38 no_clock_gettime = True
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39 return time.time()
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40
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41 t = timespec()
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42 CLOCK_MONOTONIC = 1 # see <linux/time.h>
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43
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44 if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(t)) != 0:
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45 errno_ = ctypes.get_errno()
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46 raise OSError(errno_, os.strerror(errno_))
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47 return t.tv_sec + t.tv_nsec * 1e-9
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48
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49 # decorator, tries a number of times, returns None on failure, sleeps between
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50 # Must be used as "@retry()" if arguments are defaulted
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51 def retry(retries=DEFAULT_TRIES, try_time = 1):
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52 def inner(func):
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53 def new_f(*args, **kwargs):
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54 for i in range(retries):
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55 d = func(*args, **kwargs)
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56 if d:
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57 return d
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58 time.sleep(try_time)
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59 new_f.func_name = func.func_name
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60 return new_f
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61 return inner
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62
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63 def readline(sock):
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64 timeout = READLINE_SELECT_TIMEOUT
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65 buf = ''
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66 while True:
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67 if not lightblue:
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68 (rlist, wlist, xlist) = select.select([sock], [], [], timeout)
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69 if sock not in rlist:
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70 # hit timeout
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71 return None
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72
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73 c = sock.recv(1)
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74 if c == '':
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75 # lightblue timeout
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76 return None
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77 if c == '\r':
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78 continue
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79
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80 buf += c
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81 if c == '\n':
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82 return buf
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83
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84 # from http://blog.stalkr.net/2011/04/pctf-2011-32-thats-no-bluetooth.html
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85 def crc16(buff, crc = 0, poly = 0x8408):
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86 l = len(buff)
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87 i = 0
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88 while i < l:
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89 ch = ord(buff[i])
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90 uc = 0
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91 while uc < 8:
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92 if (crc & 1) ^ (ch & 1):
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93 crc = (crc >> 1) ^ poly
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94 else:
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95 crc >>= 1
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96 ch >>= 1
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97 uc += 1
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98 i += 1
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99 return crc
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100
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101 def cheap_daemon():
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102 print "Daemonising."
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103 sys.stdout.flush()
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104 sys.stderr.flush()
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105 out = file('/dev/null', 'a+')
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106 os.dup2(out.fileno(), sys.stdout.fileno())
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107 os.dup2(out.fileno(), sys.stderr.fileno())
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108
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109 try:
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110 pid = os.fork()
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111 if pid > 0:
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112 sys.exit(0)
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113 except OSError, e:
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114 print>>sys.stderr, "Bad fork()"
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115 sys.exit(1)
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116
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117 os.setsid()
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118
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119 try:
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120 pid = os.fork()
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121 if pid > 0:
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122 sys.exit(0)
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123 except OSError, e:
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124 print>>sys.stderr, "Bad fork()"
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125 sys.exit(1)
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126
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127