annotate py/utils.py @ 143:0895f5ad7731

copied fridge logic from main.c
author Matt Johnston <matt@ucc.asn.au>
date Tue, 20 Nov 2012 22:03:10 +0800
parents 4755e6f9a5b8
children 482d7852b511
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141
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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 import logging
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7
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8 L = logging.info
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9 W = logging.warning
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10 E = logging.error
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11
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12 DEFAULT_TRIES = 3
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13 READLINE_SELECT_TIMEOUT = 1
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14
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15 clock_gettime = None
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16 no_clock_gettime = True
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17 def monotonic_time():
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18 global clock_gettime
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19 global no_clock_gettime
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20 if no_clock_gettime:
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21 return time.time()
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22
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23 class timespec(ctypes.Structure):
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24 _fields_ = [
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25 ('tv_sec', ctypes.c_long),
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26 ('tv_nsec', ctypes.c_long)
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27 ]
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28 if not clock_gettime:
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29 try:
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30 librt = ctypes.CDLL('librt.so.0', use_errno=True)
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31 clock_gettime = librt.clock_gettime
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32 clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
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33 except:
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34 W("No clock_gettime(), using fake fallback.")
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35 no_clock_gettime = True
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36 return time.time()
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37
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38 t = timespec()
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39 CLOCK_MONOTONIC = 1 # see <linux/time.h>
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40
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41 if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(t)) != 0:
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42 errno_ = ctypes.get_errno()
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43 raise OSError(errno_, os.strerror(errno_))
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44 return t.tv_sec + t.tv_nsec * 1e-9
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45
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46 # decorator, tries a number of times, returns None on failure, sleeps between
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47 # Must be used as "@retry()" if arguments are defaulted
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48 def retry(retries=DEFAULT_TRIES, try_time = 1):
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49 def inner(func):
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50 def new_f(*args, **kwargs):
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51 for i in range(retries):
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52 d = func(*args, **kwargs)
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53 if d is not None:
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54 return d
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55 time.sleep(try_time)
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56 return None
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57
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58 new_f.func_name = func.func_name
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59 return new_f
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60 return inner
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61
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62 def readline(sock):
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63 timeout = READLINE_SELECT_TIMEOUT
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64 buf = ''
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65 while True:
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66 (rlist, wlist, xlist) = select.select([sock], [], [], timeout)
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67 if sock not in rlist:
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68 # hit timeout
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69 return None
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70
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71 c = sock.recv(1)
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72 if c == '':
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73 # lightblue timeout
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74 return None
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75 if c == '\r':
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76 continue
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77
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78 buf += c
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79 if c == '\n':
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80 return buf
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81
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82 # from http://blog.stalkr.net/2011/04/pctf-2011-32-thats-no-bluetooth.html
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83 def crc16(buff, crc = 0, poly = 0x8408):
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84 l = len(buff)
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85 i = 0
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86 while i < l:
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87 ch = ord(buff[i])
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88 uc = 0
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89 while uc < 8:
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90 if (crc & 1) ^ (ch & 1):
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91 crc = (crc >> 1) ^ poly
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92 else:
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93 crc >>= 1
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94 ch >>= 1
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95 uc += 1
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96 i += 1
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97 return crc
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98
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99 def cheap_daemon():
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100 L("Daemonising.")
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101 sys.stdout.flush()
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102 sys.stderr.flush()
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103 out = file('/dev/null', 'a+')
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104 os.dup2(out.fileno(), sys.stdout.fileno())
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105 os.dup2(out.fileno(), sys.stderr.fileno())
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106
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107 try:
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108 pid = os.fork()
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109 if pid > 0:
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110 sys.exit(0)
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111 except OSError, e:
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112 E("Bad fork()")
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113 sys.exit(1)
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114
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115 os.setsid()
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116
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117 try:
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118 pid = os.fork()
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119 if pid > 0:
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120 sys.exit(0)
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121 except OSError, e:
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122 E("Bad fork()")
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123 sys.exit(1)
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124
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125