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import hashlib
def feed_file(h, f):
"""Feed data read from an open file into the hashlib instance."""
while True:
data = f.read(65536)
if len(data) == 0:
# end of file
break
h.update(data)
def feed_file_path(h, path):
"""Feed data read from a file (to be opened by this function) into the hashlib instance."""
with open(path, 'rb') as f:
feed_file(h, f)
def file_digest(algorithm, path):
"""Calculate the digest of a file and return it in hexadecimal notation."""
h = algorithm()
feed_file_path(h, path)
return h.hexdigest()
def guess_digest_algorithm(digest):
l = len(digest)
if l == 32:
return hashlib.md5
elif l == 40:
return hashlib.sha1
elif l == 64:
return hashlib.sha256
else:
return None
def verify_file_digest(path, expected_digest):
"""Verify the digest of a file, and return True if the digest matches with the given expected digest."""
algorithm = guess_digest_algorithm(expected_digest)
assert(algorithm is not None)
return file_digest(algorithm, path) == expected_digest
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