64 lines
1.9 KiB
Python
64 lines
1.9 KiB
Python
import re
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import os.path
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import hashlib
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from collections import namedtuple
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Digest = namedtuple('Digest', ['is_tarsum', 'tarsum_version', 'hash_alg', 'hash_bytes'])
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DIGEST_PATTERN = r'(tarsum\.(v[\w]+)\+)?([\w]+):([0-9a-f]+)'
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DIGEST_REGEX = re.compile(DIGEST_PATTERN)
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class InvalidDigestException(RuntimeError):
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pass
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def parse_digest(digest):
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""" Returns the digest parsed out to its components. """
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match = DIGEST_REGEX.match(digest)
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if match is None or match.end() != len(digest):
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raise InvalidDigestException('Not a valid digest: %s', digest)
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is_tarsum = match.group(1) is not None
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return Digest(is_tarsum, match.group(2), match.group(3), match.group(4))
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def content_path(digest):
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""" Returns a relative path to the parsed digest. """
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parsed = parse_digest(digest)
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components = []
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if parsed.is_tarsum:
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components.extend(['tarsum', parsed.tarsum_version])
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# Generate a prefix which is always two characters, and which will be filled with leading zeros
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# if the input does not contain at least two characters. e.g. ABC -> AB, A -> 0A
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prefix = parsed.hash_bytes[0:2].zfill(2)
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components.extend([parsed.hash_alg, prefix, parsed.hash_bytes])
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return os.path.join(*components)
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def sha256_digest(content):
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""" Returns a sha256 hash of the content bytes in digest form. """
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def single_chunk_generator():
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yield content
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return sha256_digest_from_generator(single_chunk_generator())
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def sha256_digest_from_generator(content_generator):
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""" Reads all of the data from the iterator and creates a sha256 digest from the content
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"""
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digest = hashlib.sha256()
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for chunk in content_generator:
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digest.update(chunk)
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return 'sha256:{0}'.format(digest.hexdigest())
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def digests_equal(lhs_digest_string, rhs_digest_string):
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""" Parse and compare the two digests, returns True if the digests are equal, False otherwise.
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"""
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return parse_digest(lhs_digest_string) == parse_digest(rhs_digest_string)
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