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1 import os |
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2 import time |
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3 import fcntl |
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4 import sys |
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5 |
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6 class AtomicFile(object): |
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7 DELAY = 0.5 |
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8 def __init__(self, name): |
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9 self.name = name |
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10 |
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11 def write(self, data, timeout = 5): |
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12 try: |
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13 end = time.time() + timeout |
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14 with open(self.name, "r+") as f: |
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15 while timeout == 0 or time.time() < end: |
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16 try: |
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17 fcntl.lockf(f, fcntl.LOCK_EX | fcntl.LOCK_NB) |
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18 except IOError: |
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19 time.sleep(DELAY) |
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20 continue |
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21 |
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22 f.write(data) |
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23 return True |
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24 |
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25 except IOError, e: |
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26 print>>sys.stderr, e |
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27 |
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28 return False |
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29 |
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30 def read(self, timeout = 5): |
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31 try: |
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32 end = time.time() + timeout |
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33 with open(self.name, "r") as f: |
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34 while timeout == 0 or time.time() < end: |
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35 try: |
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36 fcntl.lockf(f, fcntl.LOCK_SH | fcntl.LOCK_NB) |
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37 except IOError: |
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38 time.sleep(DELAY) |
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39 continue |
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40 |
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41 return f.read() |
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42 |
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43 except IOError, e: |
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44 print>>sys.stderr, e |
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45 |
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46 return None |
