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quay/digest/digest_tools.py

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2019-11-12 16:09:47 +00:00
import re
import os.path
import hashlib
DIGEST_PATTERN = r'([A-Za-z0-9_+.-]+):([A-Fa-f0-9]+)'
REPLACE_WITH_PATH = re.compile(r'[+.]')
REPLACE_DOUBLE_SLASHES = re.compile(r'/+')
class InvalidDigestException(RuntimeError):
pass
class Digest(object):
DIGEST_REGEX = re.compile(DIGEST_PATTERN)
def __init__(self, hash_alg, hash_bytes):
self._hash_alg = hash_alg
self._hash_bytes = hash_bytes
def __str__(self):
return '{0}:{1}'.format(self._hash_alg, self._hash_bytes)
def __eq__(self, rhs):
return isinstance(rhs, Digest) and str(self) == str(rhs)
@staticmethod
def parse_digest(digest):
""" Returns the digest parsed out to its components. """
match = Digest.DIGEST_REGEX.match(digest)
if match is None or match.end() != len(digest):
raise InvalidDigestException('Not a valid digest: %s', digest)
return Digest(match.group(1), match.group(2))
@property
def hash_alg(self):
return self._hash_alg
@property
def hash_bytes(self):
return self._hash_bytes
def content_path(digest):
""" Returns a relative path to the parsed digest. """
parsed = Digest.parse_digest(digest)
components = []
# Generate a prefix which is always two characters, and which will be filled with leading zeros
# if the input does not contain at least two characters. e.g. ABC -> AB, A -> 0A
prefix = parsed.hash_bytes[0:2].zfill(2)
pathish = REPLACE_WITH_PATH.sub('/', parsed.hash_alg)
normalized = REPLACE_DOUBLE_SLASHES.sub('/', pathish).lstrip('/')
components.extend([normalized, prefix, parsed.hash_bytes])
return os.path.join(*components)
def sha256_digest(content):
""" Returns a sha256 hash of the content bytes in digest form. """
def single_chunk_generator():
yield content
return sha256_digest_from_generator(single_chunk_generator())
def sha256_digest_from_generator(content_generator):
""" Reads all of the data from the iterator and creates a sha256 digest from the content
"""
digest = hashlib.sha256()
for chunk in content_generator:
digest.update(chunk)
return 'sha256:{0}'.format(digest.hexdigest())
def sha256_digest_from_hashlib(sha256_hash_obj):
return 'sha256:{0}'.format(sha256_hash_obj.hexdigest())
def digests_equal(lhs_digest_string, rhs_digest_string):
""" Parse and compare the two digests, returns True if the digests are equal, False otherwise.
"""
return Digest.parse_digest(lhs_digest_string) == Digest.parse_digest(rhs_digest_string)