77 lines
2.1 KiB
Python
77 lines
2.1 KiB
Python
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# Copyright 2013 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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import hashlib
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import os
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def CallAndRecordIfStale(
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function, record_path=None, input_paths=[], input_strings=[], force=False):
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"""Calls function if the md5sum of the input paths/strings has changed.
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The md5sum of the inputs is compared with the one stored in record_path. If
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this has changed (or the record doesn't exist), function will be called and
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the new md5sum will be recorded.
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If force is True, the function will be called regardless of whether the
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md5sum is out of date.
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"""
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md5_checker = _Md5Checker(
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record_path=record_path,
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input_paths=input_paths,
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input_strings=input_strings)
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if force or md5_checker.IsStale():
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function()
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md5_checker.Write()
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def _UpdateMd5ForFile(md5, path, block_size=2**16):
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with open(path, 'rb') as infile:
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while True:
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data = infile.read(block_size)
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if not data:
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break
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md5.update(data)
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def _UpdateMd5ForDirectory(md5, dir_path):
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for root, _, files in os.walk(dir_path):
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for f in files:
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_UpdateMd5ForFile(md5, os.path.join(root, f))
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def _UpdateMd5ForPath(md5, path):
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if os.path.isdir(path):
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_UpdateMd5ForDirectory(md5, path)
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else:
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_UpdateMd5ForFile(md5, path)
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class _Md5Checker(object):
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def __init__(self, record_path=None, input_paths=[], input_strings=[]):
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assert record_path.endswith('.stamp'), (
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'record paths must end in \'.stamp\' so that they are easy to find '
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'and delete')
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self.record_path = record_path
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md5 = hashlib.md5()
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for i in sorted(input_paths):
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_UpdateMd5ForPath(md5, i)
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for s in input_strings:
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md5.update(s)
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self.new_digest = md5.hexdigest()
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self.old_digest = ''
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if os.path.exists(self.record_path):
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with open(self.record_path, 'r') as old_record:
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self.old_digest = old_record.read()
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def IsStale(self):
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return self.old_digest != self.new_digest
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def Write(self):
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with open(self.record_path, 'w') as new_record:
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new_record.write(self.new_digest)
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