initial import for Open Source 🎉

digest/digest_tools.py

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+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)