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#!/usr/bin/python
# Copyright 2011 Google Inc. All Rights Reserved.
import threading
from utils import logger
from utils.file_utils import FileUtils
class ImageChecksummer(object):
class PerImageChecksummer(object):
def __init__(self, filename):
self._lock = threading.Lock()
self.filename = filename
self._checksum = None
def Checksum(self):
with self._lock:
if not self._checksum:
logger.GetLogger().LogOutput("Computing checksum for '%s'." %
self.filename)
self._checksum = FileUtils().Md5File(self.filename)
logger.GetLogger().LogOutput("Checksum is: %s" % self._checksum)
return self._checksum
_instance = None
_lock = threading.Lock()
_per_image_checksummers = {}
def __new__(cls, *args, **kwargs):
with cls._lock:
if not cls._instance:
cls._instance = super(ImageChecksummer, cls).__new__(cls,
*args, **kwargs)
return cls._instance
def Checksum(self, filename):
with self._lock:
if filename not in self._per_image_checksummers:
self._per_image_checksummers[filename] = (ImageChecksummer.
PerImageChecksummer(filename))
checksummer = self._per_image_checksummers[filename]
try:
return checksummer.Checksum()
except Exception, e:
logger.GetLogger().LogError("Could not compute checksum of file '%s'."
% filename)
raise e
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