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#!/usr/bin/python
# Copyright (c) 2012 The Native Client Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Hashing related operations.
Provides for hashing files or directory trees.
Timestamps, archive order, and dot files/directories are ignored to keep
hashes stable.
"""
import hashlib
import os
def HashFileContents(filename):
"""Return the hash (sha1) of tthe contents of a file.
Args:
filename: Filename to read.
Returns:
The sha1 of a file.
"""
hasher = hashlib.sha1()
fh = open(filename, 'rb')
try:
while True:
data = fh.read(4096)
if not data:
break
hasher.update(data)
finally:
fh.close()
return hasher.hexdigest()
def StableHashPath(path):
"""Hash (sha1) everything in a path in a stable (reproducible) way.
Dot files and timestamps are ignored.
Args:
path: Path to hash.
Returns:
The sha1 of the file/directory.
"""
hasher = hashlib.sha1()
if os.path.isfile(path):
hasher.update('singlefile:' + HashFileContents(path))
return hasher.hexdigest()
def RemoveExcludedPaths(paths):
for p in [p for p in paths if p.startswith('.')]:
paths.remove(p)
for root, dirs, files in os.walk(path):
dirs.sort()
files.sort()
RemoveExcludedPaths(dirs)
RemoveExcludedPaths(files)
# Including directory names in the hash so that
# empty directories do count.
# Also, as a side effect, all of the relative path components
# are incorporated.
# Terminating with \x00 to avoid injection attacks.
for d in dirs:
hasher.update('dir:' + d + '\x00')
for f in files:
hasher.update('filename:' + f + '\x00')
hasher.update('contents:' + HashFileContents(
os.path.join(root, f)))
return hasher.hexdigest()
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