Created
June 11, 2019 12:26
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#!/usr/bin/env python3 | |
# -*- mode: python -*- | |
import sys | |
import hashlib | |
def calculate_multipart_etag(source_path, chunk_size, expected=None): | |
md5s = [] | |
with open(source_path,'rb') as fp: | |
while True: | |
data = fp.read(chunk_size) | |
if not data: | |
break | |
md5s.append(hashlib.md5(data)) | |
if len(md5s) > 1: | |
digests = b"".join(m.digest() for m in md5s) | |
new_md5 = hashlib.md5(digests) | |
new_etag = '"%s-%s"' % (new_md5.hexdigest(),len(md5s)) | |
elif len(md5s) == 1: | |
# file smaller than chunk size | |
new_etag = '"%s"' % md5s[0].hexdigest() | |
else: | |
new_etag = '""' | |
if expected: | |
if not expected==new_etag: | |
raise ValueError('new etag %s does not match expected %s' % (new_etag,expected)) | |
return new_etag | |
if __name__ == '__main__': | |
source_path = sys.argv[1] | |
chunk_size = sys.argv[2] | |
chunk_size = int(chunk_size) * 1024 * 1024 | |
try: | |
expected = '"%s"' % (sys.argv[3]) | |
except Exception as e: | |
expected = None | |
print(calculate_multipart_etag(source_path,chunk_size,expected)) |
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