83 lines
2.4 KiB
Python
83 lines
2.4 KiB
Python
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import re
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import os.path
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import hashlib
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DIGEST_PATTERN = r'([A-Za-z0-9_+.-]+):([A-Fa-f0-9]+)'
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REPLACE_WITH_PATH = re.compile(r'[+.]')
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REPLACE_DOUBLE_SLASHES = re.compile(r'/+')
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class InvalidDigestException(RuntimeError):
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pass
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class Digest(object):
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DIGEST_REGEX = re.compile(DIGEST_PATTERN)
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def __init__(self, hash_alg, hash_bytes):
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self._hash_alg = hash_alg
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self._hash_bytes = hash_bytes
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def __str__(self):
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return '{0}:{1}'.format(self._hash_alg, self._hash_bytes)
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def __eq__(self, rhs):
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return isinstance(rhs, Digest) and str(self) == str(rhs)
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@staticmethod
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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.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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return Digest(match.group(1), match.group(2))
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@property
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def hash_alg(self):
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return self._hash_alg
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@property
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def hash_bytes(self):
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return self._hash_bytes
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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 = Digest.parse_digest(digest)
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components = []
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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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pathish = REPLACE_WITH_PATH.sub('/', parsed.hash_alg)
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normalized = REPLACE_DOUBLE_SLASHES.sub('/', pathish).lstrip('/')
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components.extend([normalized, 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 sha256_digest_from_hashlib(sha256_hash_obj):
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return 'sha256:{0}'.format(sha256_hash_obj.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 Digest.parse_digest(lhs_digest_string) == Digest.parse_digest(rhs_digest_string)
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